Article

Signalling of Nutritional Need by Magpie Nestlings

April 1992
Ethology 92(3):193 - 204

April 1992
92(3):193 - 204

DOI:10.1111/j.1439-0310.1992.tb00959.x

Authors:

Tomas Redondo

Spanish National Research Council

Francisca Castro

University of Cordoba (Spain)

The relationship between begging behaviour, chick nutritional state, and parental distribution of food within broods was studied in 4- and 5-chick magpie Pica pica broods under natural conditions. Three components of the begging display (duration, latency, and posture) were highly correlated with each other and also with the emission and duration of begging calls. Begging performance was strongly influenced by the food intake of nestlings during the preceding 1-h interval, indicating that begging may reliably reflect the nutritional need of nestlings. Daily growth during the preceding day, as well as average cumulative food intake by the brood during the preceding 24 h, seemed not to affect begging in a similar way. Begging signals employed by hungrier nestlings involved a higher degree of muscular activity, thus supporting the prediction that nestlings in greater need should employ more costly signals. Overall, those nestlings who begged more tended to obtain more food, but the relationship between feeding success and begging behaviour was weak due to a high variation between broods in the way that parents seemed to respond to variations in begging behaviour. Possible causes for this variation, and its implications for the evolution of reliable begging displays, are discussed.

Begging calls and mouth colouration as predictors of breeding success in blue tits

Article

Full-text available

Feb 2024

Nestlings normally exhibit a mix of traits that attract parental care, such as postural and vocal begging and carotenoid‐based mouth colouration. These signals are hypothesised to be signs of nestling needs (vocal begging) and quality (mouth colouration). Therefore, we hypothesised that broods, where nestlings beg for less time and display more saturated carotenoid‐based mouth colouration, would have lower nestling mortality. We tested these predictions in two wild blue tit (Cyanistes caeruleus) populations. The breeding success (here defined as the proportion of eggs that produced fledglings) was related to nestling mouth flanges' carotenoid‐based colour saturation. This means that blue tits that raised nestlings with more coloured flanges had a higher within‐population breeding success. Time spent in vocal begging, by contrast, was not associated with breeding success. Hence, our findings reveal that some communication signals displayed by nestlings (carotenoid‐based colouration) predict breeding success, in our study mostly reflecting the proportion of eggs that hatched, while begging intensity does not, probably because the former reflects a better maternal pre‐laying condition and nestling physiological status in the mid‐term.

Cooperación y conflicto entre hermanos de nido en Cigüeña Blanca (Ciconia ciconia)

Thesis

Feb 2018

Jose María Romero

Genetic conflicts among siblings in species with sexual reproduction and parental care, such as birds, manifest as sibling rivalry when nestmates compete for parental resources. Sibling competition is implemented through a diverse array of behavioural mechanisms, ranging from overt aggression and fratricide through non-virulent forms of scramble competition (e.g. begging signals) which may include a high level of tolerance among broodmates or even mutualism. Previous studies suggested that white stork (Ciconia ciconia) nestlings showed little or no aggression or physical interference as a result of parents feeding nestlings simultaneously, by regurgitating food on the nest floor. This pattern, which is shared by other stork species, is however exceptional among other bird families with close ecological and phylogenetic affinities, such as herons, ibises or pelicans. In these groups, nestmates usually compete despotically, often by overt aggression. The aims of this study were: 1) to elucidate the precise behavioural mechanisms regulating nestmate competition and communication within white stork broods, and 2) to unravel the ultimate evolutionary causes underlying variation in levels and mechanisms of nestmate competition among the highly diverse clade of subaltricial birds. First, we obtained behavioural samples from video recordings of natural feeding events involving 108 nestlings from 46 broods less than four weeks old, as well as data from three experimental setups. Second, we performed a phylogenetic comparative study based on a dataset including 192 species belonging to 16 families of altricial birds to determine ecological, behavioural and life-history predictors of the level of interference competition among nestmates. Results showed that white stork broods are characterized by a high level of broodmate tolerance, where interference competition is weak if not completely absent. Moreover, white stork nestlings display an elaborate repertoire of signals containing information about chick nutritional state which seem to be involved in cooperative begging and sibling negotiation, which suggests a highly prosocial evolutionary scenario. The comparative study revealed that the observed diversity in levels of interference competition among subaltricial birds is closely linked to a species’ life history: more virulent sibling rivalry is associated with a slow life history pace (low fecundity and mortality rates). It is suggested that this association is mediated by both short- and, specially, long-term effects of early nestling behaviour upon viability and fecundity later in life.

Effect of variation in nestling hunger levels on the begging behavior of nestlings and the provisioning behavior of adult American Kestrels

Thesis

Full-text available

Aug 2015

Katheryn Watson

Little is known about how variation in nestling begging intensity influences the behavior of adult raptors and how responses of adult males and females to such variation might differ. My objective was to manipulate the begging intensity of nestling American Kestrels (Falco sparverius) and examine the responses of adult males and females. I studied 12 pairs of kestrels nesting in nest boxes from 1 March to 1 July 2014 at the Blue Grass Army Depot, Madison County, Kentucky. Nest boxes were modified with a separate compartment for a camcorder to record nestling behavior, and a second camcorder was placed outside of nests to monitor adult behavior. To manipulate nestling hunger levels, 12 to 26-day-old nestlings in six nests were deprived of food for 24 hours and those in the other six nests were fed until satiated. At each nest, I alternated control (no treatment) and treatment (fed or food-deprived) days (control, treatment, control, and treatment) over a four-day period to minimize the possible effect of nestling age on adult and nestling behavior. Each day, nestlings and adults were video-recorded for four hours. Recordings were subsequently reviewed and, to quantify begging behavior, I: (1) determined the proportion of nestlings in broods begging when adults arrived at and left nests, (2) categorized begging intensity of each nestling as 0 (no gaping), 1 (gaping), 2 (gaping with neck extended), or 3 (wings flapping vigorously) when adults arrived at and left nests, and (3) noted how long nestlings continued to utter begging calls after adults left nests. I also determined the provisioning rates of adult males and females. Analysis revealed that the proportion of nestlings begging when adults arrived at nests did not differ among treatments (food-deprived, fed, and control; P = 0.057), but did differ at adult departure (P = 0.0002), with a smaller proportion of nestlings in the fed-treatment nests begging after being fed. Nestling begging intensity differed among treatments both when adults arrived at (P = 0.0011) and left nests (P < 0.0001), with nestlings in fooddeprived nests begging with greater intensity after food deprivation and those in fedtreatment nests begging with less intensity after being fed. In addition, food-deprived nestlings continued uttering begging calls longer (P = 0.007) after deprivation than during control periods. Adult male and female kestrels fed nestlings at similar rates (P = 0.10), v i and they fed nestlings (P = 0.0009) at higher rates after food deprivation than during control periods and at lower rates after fed treatments than during control periods. Adults provisioned food-deprived nestlings (mean = 4.2 visits/nestling/hour) at nearly four times the rate of satiated nestlings (mean = 1.1 visits/nestling/hour). My results suggest that the begging behavior of nestling American Kestrels varies with hunger level and is an honest signal of nestling need, and that adult kestrels respond to changes in nestling hunger levels by adjusting provisioning rates. Although the responses of adult kestrels to variation in nestling begging behavior suggest that natural selection might favor ‘dishonest’ begging by nestlings, i.e., begging with greater intensity to obtain more food, the potential costs of ‘dishonest’ begging may outweigh any possible benefit, e.g., increased likelihood of attracting predators and loss of indirect fitness benefits if increased begging has negative impacts on the condition of siblings and parents.

Begging behavior and host exploitation in parasitic cowbirds

Article

Full-text available

Jan 2002

Effect of Variation in Nestling Hunger Levels on the Begging Behaviour of Nestlings and the Provisioning Behaviour of Adult American Kestrels

Article

Full-text available

Jan 2018

Little is known about how variation in nestling begging intensity influences the behaviour of adult raptors and how responses of adult males and females to such variation might differ. Our objective was to manipulate the begging intensity of nestling American Kestrels (Falco sparverius) and examine the responses of adults. We studied 12 pairs of American Kestrels nesting in nest boxes from 1 March to 1 July 2014 at the Blue Grass Army Depot, Madison County, Kentucky. Nest boxes were modified with a separate compartment for a camcorder to record nestling behaviour, and a second camcorder was placed outside the nests to monitor adult behaviour. To manipulate nestling hunger levels, 12 to 26-day-old nestlings in six nests were deprived of food for 24 h and those in the other six nests were fed until satiated. At each nest, we alternated control (no treatment) and treatment (fed or food deprived) days over a 4 day period to minimise the possible effect of nestling age on adult and nestling behaviour. Nestling begging intensity differed among treatments, with nestlings in food-deprived nests begging with greater intensity after food deprivation and those in fed-treatment nests begging with less intensity after being fed. Adult male and female American Kestrels provisioned nestlings at similar rates, with both sexes feeding nestlings at higher rates after food deprivation and at lower rates after fed treatments. Thus, the begging behaviour of nestling American Kestrels varied with hunger level, and adult American Kestrels responded by adjusting provisioning rates. Although the response of adults to nestling begging suggests that natural selection might favour 'dishonest' begging to obtain more food, the potential costs of 'dishonest' begging, such as attracting predators, reduced immunocompetence, and loss of indirect fitness benefits if such begging negatively impacts siblings and parents, may outweigh any possible benefit.

Begging and Parental Care in Relation to Offspring Need and Condition in the Barn Swallow (Hirundo rustica)

Article

Dec 2000

Parents are selected to maximize their fitness by allocating care among their progeny in relation to the differential reproductive value of offspring. Nestlings have been hypothesized to signal need for parental care reliably through their begging behavior, but offspring condition as reflected by their reproductive value may likewise affect begging and hence provisioning. We assessed the relative importance of need and condition in determining begging behavior and feeding rate of nestling barn swallows (Hirundo rustica) through short‐term starvation, a challenge to their immune system with a foreign antigen negatively affecting condition, and brood size manipulation. Food deprivation but not condition or brood size manipulation increased nestling begging rate. Parents fed offspring depending on both need and condition but only when feeding broods that were reduced or of normal size. In enlarged broods, offspring received less food per capita than in reduced broods, and parents did not discriminate among nestlings relative to their need or condition. Thus, nestlings signal their need by increased solicitation. Parents allocate food to offspring dependent on both need and condition, with these effects depending on parental workload as determined by experimental brood size.

Decoding colouration of begging traits by the experimental addition of the appetite enhancer cyproheptadine hydrochloride in magpie ( Pica pica ) nestlings

Article

Full-text available

Jul 2016
J AVIAN BIOL

The colouration of some traits in nestlings of altricial birds may influence parental food allocation as it may reflect physical condition or hunger. There is increasing evidence of the relationship between colouration of begging traits and nestling performance. However, evidence of the influence of hunger level on nestling colouration is scarce, mainly because of difficulty of distinguishing between the effects of physical condition and hunger levels. Here, we used the appetite stimulant cyproheptadine hydrochloride to increase the sensation of hunger of magpie (Pica pica) nestlings for eight days and assessed the effect on the colouration of rictal flanges, mouth and body skin. We found that nestlings administered with cyproheptadine had flanges more conspicuous (chromatic visual contrast), more UV coloured and less yellow coloured than their control nestmates. Conversely, mouths of experimental nestlings were more yellow coloured and less UV coloured than controls. Our pharmacological experiment affected the strength of the relationship between body mass and some colour components of body skin (chromatic and achromatic visual contrasts, UV–chroma and Yellow– chroma) and of rictal flanges (chromatic visual contrasts, UV–chroma and yellow– chroma), but not for mouth colouration. These results taken together suggest that the effect of the cyproheptadine on nestling colourations is probably mediated by an increase in hunger levels of nestlings for rictal flanges and body skin colourations, and by an increase in physical condition in the case of mouth coloration.

Equivocal responses to experimental brood sizes in a hawk-cuckoo host: brood size as a reference for parental provisioning decisions?

Article

May 2016
ETHOLOGY

The number of offspring surviving until independence is the fundamental drive in the evolution of parental care. Because of the related costs, parental investment must be balanced with essential resources for parents themselves, among the resources available in the environment under the current parental condition. It is advantageous for parents to adjust their level of investment to the number of offspring; however, there is little evidence that parents employ numerical competence in adjusting their investment level. We investigated how parents respond to experimentally manipulated brood sizes in a passerine species, known as a host of a brood parasitic cuckoo whose chicks presumably deceive their hosts numerically. Parents reduced their provisioning to broods of reduced sizes, whereas parents did not increase provisioning to enlarged broods compared to that in the control condition. These parental responses can be attributed to the response of chicks to the experimental treatments compared to that in the control: chicks lowered begging intensity in the reduced condition, while they did not intensify being in the enlarged condition. Further analyses revealed that eagerness of parents to respond to chick begging intensity differed between the experimental treatments: strong parental response was detected toward begging chicks only in the reduced condition. We propose that the detected equivocality of parental responses might be related to the difference in the number of chicks between the unmanipulated and experimentally manipulated broods, the former reflecting the initial parental decision on the amount of resources to allocate to the brood.

Convergent characteristics of begging vocalisations in Australian birds

Article

Full-text available

Jun 2003

Mark A. Jurisevic

The acoustic structure and sound pressure level (i.e. loudness) of begging calls from nestlings and fledglings were examined for 12 species of Australian passerines and three species of parrots. There was a great deal of variation in the acoustic structure of the begging calls between species. Some calls were quite short in duration (0.06-0.1 s) while others were very long (0.98-1.51 s). However, most begging calls were loud and covered a wide range of frequencies consisting of noisy and/or harmonic components. These acoustic characteristics, which were observed in all species, presumably allow for efficient detection and location of the calling bird by parents, as well as signalling the birds' nutritional requirements. The potential negative consequences of producing these vocalisations are an increased risk of detection by predators and a high metabolic cost. The findings of this study suggest that the potential risks associated with begging in Australian birds are offset by the benefits gained from producing loud, wide band vocalisations that can be easily detected and located by parents.

Parental influence on begging call structure in zebra finches ( Taeniopygia guttata ): evidence of early vocal plasticity

Article

Full-text available

Nov 2015

Begging calls are signals of need used by young birds to elicit care from adults. Different theoretical frameworks have been proposed to understand this parent-offspring communication. But relationships between parental response and begging intensity, or between begging characteristics and proxies of a young's need remain puzzling. Few studies have considered the adjustment of nestling begging features to previous experience as a possible explanation of these discrepancies. In this study, we tested the effect of a heterospecific rearing environment on individual developmental trajectories of the acoustic structure of nestling begging calls. Fifty-two zebra finch chicks were fostered either to Bengalese finch or to zebra finch parents, and begging calls were recorded at several stages of nestling development. Acoustic analyses revealed that the development of the spectral features of the begging calls differed between experimental conditions: chicks reared by Bengalese finches produced higher pitched and less broadband begging calls than chicks reared by conspecific parents. Differences were stronger in males than females and were not explained by differences in growth rate. We conclude that nestling begging calls can be plastic in response to social interactions with parents.

Parent-absent calls are related to nestling reaction time and parental food allocation in the spotless starling

Article

Jul 2015
BEHAVIOUR

Absent repeat calls (ARC) are produced by nestlings of some bird species when parents are not at the nest, and play a role in sibling interactions and parental investment. We explored if individual traits influencing begging also determine ARC in the spotless starling (Sturnus unicolor), and whether this behaviour explains nestling feeding success. We video-taped natural broods and examined the effects of experimental feeding in this behaviour. Experimentally fed chicks stopped calling and received fewer feedings. Among un-fed chicks, absence calls were more frequent in smaller nestlings. We found a positive relationship between nestling reaction time to parental arrival and food acquisition: chicks that reacted first received more feedings that slower chicks. ARC performance was also positively related to reaction time: chicks that produced more calls also reacted first to parents. These results suggest that ARC may have important effects on resource allocation and family interaction networks.

Breeding and begging behaviour in the Plain Laughingthrush

Article

Full-text available

Nov 2023

Simple Summary Food allocation among nestlings of altricial birds is crucial for understanding the evolution of parent–offspring conflicts within avian families. Empirical studies have yet to reach a consensus on whether parents or offspring determine the food distribution within the brood. In the case of the Plain Laughingthrush (Garrulax davidi), we explore the relationship between parental feeding strategies and nestling begging behaviors. Due to hatching asynchrony, larger nestlings often outcompete their smaller siblings for food, although they do not consistently exhibit higher begging intensity. Generally, nestlings with the highest begging intensity are more likely to be fed first, underscoring the importance of nestling begging in parental food allocation. However, if the initial food recipients are already satiated and do not immediately consume the food, parents reallocate it to other nestlings. This re-feeding tactic reduces the chance of early-hatched nestlings monopolizing food due to their larger size. Our research demonstrates that, while parental food allocation primarily depends on nestling begging intensity, the decision to re-feed hinges on whether the initial recipients promptly ingest the food. Abstract Investigation on food allocation among nestlings of altricial birds is crucial in understanding parent–offspring conflicts within avian families. However, there is no consensus in empirical studies regarding whether parents or offspring determine the food allocation pattern within a brood. In the Plain Laughingthrush (Garrulax davidi), we examine the relationship between parental feeding strategies and nestling begging behaviors. Due to hatching asynchrony, larger nestlings have a competitive advantage in food acquisition over their smaller brood-mates; nevertheless, if the initial food-receivers were already satiated and did not immediately consume the food, parents would retrieve the food and re-allocate it to another nestling. This re-feeding tactic employed by parents reduced the likelihood of early-hatched nestlings monopolizing the food solely due to their larger body size. Our findings indicate that parents primarily allocated food based on nestling begging intensity, while their re-feeding tactic is determined by whether the first food-receivers have consumed the food. To date, our research demonstrates that while parental food allocation primarily hinges on the begging intensity of the nestlings, the decision to re-feed is contingent upon whether the initial recipients of the food ingest it immediately.

Passive and active parental food allocation in a songbird

Article

Full-text available

May 2023
BEHAV ECOL

Parent-offspring conflict over food allocation can be modeled using two theoretical frameworks: passive (scramble competition) and active choice (signaling) resolution models. However, differentiating between these models empirically can be challenging. One possibility involves investigating details of decision-making by feeding parents. Different nestling traits, related to competitive prowess or signaling cryptic condition, may interact additively or non-additively as predictors of parental feeding responses. To explore this, we experimentally created even-sized, small broods of pied flycatchers and manipulated nestling cryptic quality, independently of size, by vitamin E supplementation. We explored how interactions between nestling cryptic condition, size, signals, and spatial location predicted food allocation and prey-testing by parents. Parents created the potential for spatial scramble competition between nestlings by feeding from and to a narrow range of nest locations. Heavier supplemented nestlings grew faster and were more likely to access profitable nest locations. However, the most profitable locations were not more contested, and nestling turnover did not vary in relation to spatial predictability or food supply. Postural begging was only predicted by nestling hunger and body mass, but parents did not favor heavier nestlings. This suggests that size-mediated and spatial competition in experimental broods was mild. Pied flycatcher fathers allocated food in response to nestling position and begging order, while mothers seemingly followed an active choice mechanism involving assessment of more complex traits, including postural intensity interacting with order, position, and treatment, and perhaps other stimuli when performing prey-testings. Differences in time constraints may underlie sex differences in food allocation rules.

Evolutionary dynamics of hyperbolic language

Article

Full-text available

Feb 2023
PLOS COMPUT BIOL

Madison S. Krieger

Models of evolution of simple languages have typically assumed full alignment of the speaker and listeners interests, with perfect understanding representing the optimal outcome for both parties. In more realistic settings, communicating individuals will often desire different outcomes from one another. Previous work has shown that misalignment of speaker-listener interests reduces the maximum informativeness among Nash-equilibrium languages, and that multiple equilibrium languages (with different degrees of informativeness) are supported. We study the stochastic evolutionary dynamics of signaling games in which the alignment of speaker-listener interests can vary. We find that increased misalignment of speaker-listener interests is associated with a decrease in information transmission. Moreover, the most common languages to evolve are typically the most informative languages supportable as static Nash equilibria, suggesting a solution to the 'equilibrium selection problem'. In addition, our dynamics reveal the mechanism by which less informative languages evolve: words that previously signaled intense states come to be used hyperbolically for less intense states, with listeners' interpretation of these newly-ambiguous words evolving downward in response. We ground our results in linguistic data on intensifiers such as so and very, words which have unique dynamics-with constant recycling and innovation that match our theoretical results well.

Begging is an honest signal of hunger in a communally nesting bird with low genetic relatedness

Article

Full-text available

Oct 2022
BEHAV ECOL SOCIOBIOL

Kin selection theory predicts that conflict over resource allocation will intensify as relatedness between dependent young and adult caregivers decreases. As inclusive fitness constraints on dishonest signalling relax, begging behaviour is less likely to be a reliable indicator of hunger or condition. Therefore, dishonest signalling is expected to be especially prevalent in communally breeding species, for which offspring survival often depends on care from both related and unrelated adults. We evaluated the scope for conflict and its consequences for dishonest signalling in the greater ani (Crotophaga major), a communally nesting cuckoo in which multiple unrelated pairs lay in the same nest. Using video recordings of nearly 2500 feeding events across 10 nests, we demonstrate that begging behaviour is a reliable signal of hunger, with hungrier nestlings begging more intensely. We also show that begging may communicate reliable information about condition in the long term, with smaller nestlings begging more intensely than their larger broodmates. Ultimately, larger nestlings and those who begged more intensely were more likely to receive food, indicating that both begging signals and scramble competition influence resource allocation. Together, our results indicate that honest begging signals can persist even when caregivers and young are unrelated. Significance statement Offspring solicit food from their adult caregivers through a variety of begging behaviours. These behaviours can convey important information about offspring hunger and/or long-term condition, but may be exaggerated, if offspring attempt to gain more than their proportionate share of resources. We examined whether offspring exaggerate their begging behaviour, such that it is not a reliable indicator of their hunger or condition, in the greater ani. Greater anis breed communally, with multiple pairs sharing a single nest simultaneously such that nestlings are fed by both their parents and unrelated adult caregivers. Theory predicts that begging should be less reliable if offspring and caregivers are unrelated, but we found that greater ani begging behaviour reliably communicated hunger, and potentially long-term condition, to adults. This study is the first to evaluate begging signal reliability in a communally breeding species.

Coloration of spotless starling nestlings shows genetic and environmentally determined characteristics while begging for food

Article

Nov 2020

Similar to other signals, coloration of traits expressed by nestlings while they are begging for food are assumed to reflect their phenotypic conditions, and, therefore, they should be environmentally determined. However, these colorations are also species specifics and, thus, a genetic component explaining the evolution of nestling coloration should exist; a possibility rarely explored in the literature. Cross‐fostering experiments allowed us to quantify genetic and environmental components of coloration of mouth, flanges and skin in a spotless starling Sturnus unicolor population. In addition, by supplementing some nestlings within each brood with non‐pigmented antioxidants (Vitamin E or Vitamin complex), we explored the effects of food supplementation on coloration of begging‐related traits and plasma carotenoid concentration. We detected significant genetic components of colorations of skin and mouth, but not of flanges or plasma carotenoid concentration. Moreover, experimental supplementation with Vitamin E affected UV coloration of mouth, flanges and skin, while vitamin‐complex supplementation exclusively affected flange coloration. Furthermore, coloration of flanges, but not that of other traits, predicted plasma carotenoid concentration suggesting a direct link between these two traits. All these results suggest that coloration of begging‐related traits is a multifaceted signal informing parents about genetic characteristics, and of short‐term needs of nestlings, including antioxidative capacity, that parents could use to adjust feeding efforts, and deciding which chick to feed. Future research should focus on the parents' perspective, taking into account their feeding effort and feeding preferences in relation to genetically and/or environmentally determined coloration of begging‐related traits. A free Plain Language Summary can be found within the Supporting Information of this article

HATCHING ASYNCHRONY, BROOD REDUCTION, AND FOOD LIMITATION IN A NEOTROPICAL PARROT

Article

Full-text available

May 1997

A number of hypotheses for hatching asynchrony suggest that the size hierarchy among nestlings produced by hatching asynchrony is adaptive and confers benefits to parents. We assessed the costs and benefits of asynchronous hatching in the Green-rumped Parrotlet (Forpus passerinus), a small Neotropical parrot that hatches large clutches very asynchronously. We manipulated eggs to create broods of four, six, or eight young that hatched synchronously or asynchronously. In a second experiment, we tested whether food limits offspring survival by experimentally feeding later hatched young in large asynchronous broods. We also examined the premise that food varies unpredictably by sampling seeds throughout several breeding seasons. Experimentally synchronized broods generally fledged as many or more young than asynchronous broods. Synchrony particularly outperformed asynchrony in broods of eight, where food demands should have been greatest. Nestlings had a higher probability of fledging from synchronous broods than from asynchronous broods, from small rather than medium or large broods, and if they were early hatched rather than later hatched. Most mortality in asynchronous broods occurred within 12 d of hatching, and a significantly greater proportion of later hatched chicks died with empty crops than did early hatched chicks. Later hatched chicks grew more slowly than their earlier hatched nestmates, but at fledging they were as heavy or heavier than earlier hatched chicks. Chicks from asynchronous broods were slightly heavier at fledging than synchronous chicks, but there was no correlation between fledging mass and the likelihood of being resighted in subsequent years. Cormack-Jolly-Seber model estimates revealed no significant differences in annual survival rates between young fledged from synchronous and asynchronous broods. Female chicks fledged from synchronous broods were recruited into the study population at a lower rate than those from asynchronous broods. Older chicks from reduced broods were less likely to fledge than chicks from broods that fledged all their young. Parents of large synchronous and asynchronous broods provisioned their young at similar rates and did not differ significantly in their subsequent survival. Females that raised experimentally synchronous and asynchronous broods showed no significant differences in the likelihood, timing, or success of their next breeding attempt. A marginally higher proportion of last-hatched chicks that received supplemental food survived to fledging than last-hatched control chicks, but feeding had no effect on penultimate chicks. Seed densities showed a high degree of autocorrelation over spans of 30–50 d. Asynchronous hatching appears to result in the mortality of the smallest young, due in part to the inequitable distribution of food among nestmates, rather than to food limitation, and as a direct result of the size disparities among nestmates. Thus, parrotlet parents appeared to derive no detectable short- or long-term benefits from the staggered hatching of their young through increased nestling growth and survival, reduced parental efforts, or increased parental survival. Although other adaptive benefits from hatching asynchrony are possible that were not tested directly in these experiments (e.g., ‘‘insurance’’ that some nestlings will survive), they seem insufficient to account for the extreme hatching asynchrony observed in the parrotlet. Instead, benefits to egg survival derived from the early onset of incubation may offset the costs of asynchronous hatching.

Variable parental responses to changes in offspring demand have implications for life history theory

Article

Full-text available

Aug 2019
BEHAV ECOL SOCIOBIOL

Parental care, a component of reproductive effort, should evolve in response to its impact on both offspring and parent fitness. If so, manipulations in brood value should shift levels of care in predictable ways, provided that appropriate cues about the change in offspring value are altered. Prior brood size manipulations in birds have produced considerable variation in responses that have not been fully investigated. We conducted paired, short-term (2 h) reductions and enlargements in brood size (± 2 nestlings) of house sparrows in each of 4 years. Parents at reduced broods shifted parental care downward in all four seasons. Parents experiencing increased broods responded significantly variably across years; in some, they increased care, but in others, they decreased care compared with control periods. Nestlings in both treatments gained less mass than during control sessions, with year producing variable effects. We found evidence that parents experiencing reduced broods behave as if recurring predation is a risk, but we found no evidence that parents with enlarged broods were responding to inappropriate cues. Instead, parent sparrows may be behaving prudently and avoid costs of reproduction when faced with either broods that are too small or too large. We modified a published model of optimal care, mimicked our empirical manipulation, and found that the model replicated our results provided cost and benefit curves were of a particular shape. Variation in ecology among years might affect the exact nature of the relationship between care and either current or residual reproductive value. Other data from the study population support this conclusion. Significance statement Parent animals often adjust their levels of care in response to manipulations of offspring value, but considerable variation in these responses exists. This suggests either a mismatch between manipulation and natural cues or undetected subtleties in the fitness consequences of care. Over 4 years, we conducted manipulations of offspring number in the biparental house sparrow (Passer domesticus). We found little evidence that parents misinterpreted cues regarding the change in number, but they behaved differently depending on the year of the manipulation. A model recovered the observed patterns if a parameter influencing the curve relating offspring fitness to levels of care was altered. This parameter should vary with food supply, and our data suggested that this varied in the years of our study. Our results emphasize that predictions about patterns of parental care are risky without attending to the shapes of fitness curves and that some organisms may be particularly sensitive to food supply.

Bioacoustic monitoring of animal vocal behavior for conservation

Article

Full-text available

Jun 2019

The popularity of bioacoustics for threatened species monitoring has surged. Large volumes of acoustic data can be collected autonomously and remotely with minimal human effort. The approach is commonly used to detect cryptic species and, more recently, to estimate abundance or density. However, the potential for conservation‐relevant information to be derived from acoustic signatures associated with particular behavior is less well‐exploited. Animal vocal behavior can reveal important information about critical life history events. In this study, we argue that the overlap of the disciplines of bioacoustics, vocal communication, and conservation behavior—thus, “acoustic conservation behavior”—has much to offer threatened species monitoring. In particular, vocalizations can serve as indicators of behavioral states and contexts that provide insight into populations as it relates to their conservation. We explore the information available from monitoring species' vocalizations that relate to reproduction and recruitment, alarm and defense, and social behavior, and how this information could translate into potential conservation benefits. While there are still challenges to processing acoustic data, we conclude that acoustic conservation behavior may improve threatened species monitoring where vocalizations reveal behaviors that are informative for management and decision‐making.

Context-dependent strategies of food allocation among offspring in a facultative cooperative breeder

Article

Full-text available

Apr 2019

Natural selection should favor adoption of parental strategies that maximize fitness when allocating investment among offspring. In birds, begging displays often convey information of nestling need and quality, allowing parents to make adaptive food allocation decisions. We investigated how adults utilized cues likely to represent nestling competitive ability (begging position) and need (begging intensity) and a cue independent of nestling control (nestling sex) to distribute food among nestlings in a facultative cooperative breeder, the black-throated tit (Aegithalos concinnus). We found that parents reduced their efforts when helped, suggesting that parents of helped broods would have the potential to satisfy nestling needs more than unhelped parents. This suggestion was supported by the fact that nestling mass increased faster in helped than in unhelped nests. We found no effect of nestling sex on food allocation, but, as predicted, we found that adults responded differently to begging signals in relation to the presence of helpers and brood size. First, helped parents were more responsive to nestling begging intensity than parents without helpers. Second, female parents and helpers had a stronger preference for nestling begging position in large than in small broods. Third, the preference for nestling begging position was greater for unhelped than for helped female parents. These results provide evidence that carers adjust their preference for different offspring begging signals based on availability of food resources.

Positive association between facial and vocal femininity/masculinity in women but not in men

Article

Apr 2019
BEHAV PROCESS

Multicomponent stimuli improve information reception. In women, perceived facial and vocal femininity-masculinity (FM)are concordant; however, mixed results are found for men. Some feminine and masculine traits are related to sex hormone action and can indicate reproductive qualities. However, most of the current research about human mate choice focuses on isolated indicators, especially visual assessment of faces. We therefore examined the cross-modal concordance hypothesis by testing correlations between perceptions of FM based on facial, vocal, and behavioral stimuli. Standardized facial pictures, vocal recordings and dance videos of 38 men and 41 women, aged 18–35 years, were rated by 21 male and 43 female students, aged 18–35 years, on 100-point scale (0 = very feminine; 100 = very masculine). All participants were Brazilian students from University of Sao Paulo. In women, facial and vocal FM correlated positively, suggesting concordant information about mate quality. Such results were not found in men, indicating multiple messages, which agree with women's multifaceted preference for male FM. In both sexes, FM of dance did not correlate with voices or faces, indicating different information and distinct process of development. We thus partially supported the cross-modal concordance hypothesis.

Does host-absent vocalisation of common cuckoo chicks increase hosts’ food provisioning behaviour?

Article

Full-text available

Jul 2018
BEHAV ECOL SOCIOBIOL

Parent-absent vocalisation is produced by nestlings of several bird families when the parents are away from the nest. An analogous behaviour, host-absent vocalisation, has been found in some species of avian brood parasites and there are several explanations why this behaviour could have evolved. Using playback experiments, we examined whether polygynous great reed warblers (Acrocephalus arundinaceus) adjust their food provisioning behaviour in response to host-absent begging vocalisation uttered by the common cuckoo (Cuculus canorus) chicks. We found that both on monogamous and polygynous nests, host pair members responded to the broadcasted parasite begging signals by increasing their feeding rates; yet, they did not deliver larger volumes of food as a consequence of somewhat smaller prey brought per visit. Nevertheless, we propose that host-absent vocalisation of the common cuckoo chick may still represent a signal of hunger that may compensate for other, deficient components of parasite begging display. However, the efficiency of this signal may be limited by the foster parents’ provisioning abilities and local prey availability. Significance statement Bird chicks beg loudly for food when their parents are at the nest, as well as when the parents search for food elsewhere. The same applies to young parasites raised by their hosts. Experimental playback of host-absent begging calls of cuckoo chicks increased great reed warbler feeding frequency but had no effect on the volume of food delivered. Host-absent vocalisation may represent signal of hunger; however, its effectiveness may be limited by provisioning abilities of the hosts.

Influencias ambientales en la expresión y selección de caracteres melánicos en el cernícalo vulgar (Falco tinnunculus)

Thesis

Full-text available

Sep 2017

David López-Idiáquez

The animal kingdom is a constant source of conspicuous structures and behaviours that have drawn the attention of the scientific community. These traits play a crucial role in animals’ life, since they are the pillars where communication systems lay on and help individuals to resolve many conflicts, both within and between species. Animal communication can occur by very different means, but always in a bidirectional fashion that involves a sender, modulating the behaviour of the receiver. When the communication process occurs among individuals of a given species, signalling takes place in different contexts, depending on the interests of signallers and receivers. For example, signallers and receivers can share interests, as fitness benefits of one part may depend upon the fitness benefits of the other. This scenario can be found when individuals involved in the communication process are genetically related, like for instance, between parents and offspring. Alternatively, the interests of signallers and receivers can collide, when individuals compete for limited resources for example. Finally, the interests of signallers and receivers can diverge. For instance, during mate choice, males signal their quality aiming to obtain as many females as they can, while females may use these signals to find a single male of the highest quality. However, an essential requirement to obtain stable communication systems, is that the signals has to be a reliable proxy of individual condition. Signal honesty is based on the differential cost of production or maintenance paid by low and high quality individuals. Form an evolutionary perspective, the presence of stable communication systems is indicative that, at least in average, the signals used in them are reliable. If they were not reliable, Natural Selection will favour individuals that not react to those dishonest signals and, in the end, the communication system vanishes. It is easy to realise that all individuals within a single species do not exhibit the same traits with equal intensity, as can be seen for example, in the antlers of red deer. The most obvious difference is that in this species, males and not females show conspicuous antlers. In addition, among males there is also a variance in the size of their antlers depending on different individual characteristics. This example perfectly illustrates that the expression of a certain trait, secondary sexual in this case, is determined by several factors, that can be inherent to the individual, like sex or age, or be associated with environmental heterogeneity, like food availability. Besides, these factors do not act in isolation, and they can interact between them. The study of the factors that modulate signal expression is crucial to understand both, the message that is transmitted and the evolutionary pressures behind the expression of the trait. The use of colour-based traits is one of the most typical ways of signalling. Among terrestrial animals, birds are of the most coloured groups, exhibiting traits varying in multiple colours and shapes. These colourations can be grouped in two different categories. First, pigmentary colouration, whose physiological origin occurs by the deposition of pigments like melanin or carotenoids. Second, structural colouration, in which colours are generated by the interaction of the microscopic structure of the feather and light, as for example the iridescent gorgets present in many hummingbirds. Melanin-based traits are one of the most common in the animal kingdom. This pigment is responsible of many colours, however, melanins are, usually, associated with colours like black, grey, brown and reddish-brown. Melanins are generated from the amino acid tyrosine, in a process known as melanogenesis. In this process, two different types of melanin can be produced, eu-melanin and pheo-melanin, that are responsible of blackish and brownish colorations respectively. Melanin-based traits have a crucial role within animal communication. It has been, for example, shown that the presence of certain melanin-based traits can be used by females to choose their mates during mate choice, reflect individual age or reliably show individual quality to name some. Still, the main role of these traits has been pointed towards a signalling function of the individual status, showing the competitive capabilities of the bearers. In this thesis, I describe the different mechanisms and functions associated with the expression melanin-based traits, using the common kestrel (Falco tinnunculus) as study species. Kestrels are medium-sized diurnal raptors, exhibiting a reversed sexual dimorphism, where males are 20% smaller than females. In addition, they also are dimorphic in coloration, males being more conspicuous than females. Specifically, males have grey heads, rump and tails, and brown bodies with a variable number of black spots covering it. Females exhibit duller plumages, mostly brown with black bars in the body, except in the rump and tail, where they can present a variable proportion of grey colouration. Kestrels have a homogeneous distribution in the Iberian Peninsula, and our study areas are located in central Spain. First, Campo Azálvaro region, located between Segovia and Ávila, there are 62 nest-boxes that have been subjected to an individual-based monitoring since 1994. Second, with the aim of increasing the number of observations and the environmental heterogeneity, we also studied a kestrel population located in Villalar de los Comuneros (Valladolid) during the experiment performed in Chapter IV. The pivotal point of this thesis is to study the factors that modulate the expression of different melanin-based traits and their function in different environments. These aspects are developed in 5 different chapters, in addition to a general introduction (Chapter I). The first two are focused on exploring the factors that modulate the expression of melanin-based traits: - In Chapter II, I explore how age and environment modulate the expression of the number and size of the spots shown in the plumages of adult males and females. - In Chapter III, I study the influence of the above-mentioned factors in a different trait, rump colouration, only in adult females, as is the sex where there is variation in the expression of this trait.In the remaining three chapters, we explored the function that melanin-based traits have during different stages of kestrels’ life-cycles. - In Chapter IV, I focus on the role of female rump colouration as a signal of status within an intra-sexual competition context during the pre-laying period. - In Chapter V, I explore the association between the duration of the post-fledgling dependence period, offspring rump colouration and survival rates to the first winter. In addition, I study the influence that this period has on future reproduction of parents. - In Chapter VI, I explore the role of plumage and rump colouration as personality index during the nestling growth. Finally, in Chapter VII, I present and discuss in an integrative manner the main results obtained in this thesis.

No evidence that kin selection increases the honesty of begging signals in birds

Article

Full-text available

Aug 2017

Providing plausible mechanisms to explain variation in the honesty of information communicated through offspring begging signals is fundamental to our understanding of parent–offspring conflict and the evolution of family life. A recently published research article used comparative analyses to investigate two long-standing hypotheses that may explain the evolution of begging behavior. The results suggested that direct competition between offspring for parental resources decreases begging honesty, whereas indirect, kin-selected benefits gained through saving parental resources for the production of future siblings increase begging honesty. However, we feel that evidence for a role of kin selection in this context is still missing. We present a combination of arguments and empirical tests to outline alternative sources of interspecific variation in offspring begging levels and discuss avenues for further research that can bring us closer to a complete understanding of the evolution of offspring signaling.

Western bluebird parents preferentially feed hungrier nestlings in a design that balances location in the nest

Article

Full-text available

Mar 2017
BEHAV ECOL SOCIOBIOL

Parents may feed nestlings based on positional cues resulting from sibling competition for favored positions at the front of a nest cavity, or they may assess begging intensity regardless of location within the nest. We independently manipulated proximity to the nest entrance and hunger level to determine whether western bluebird (Sialia mexicana) parents favor hungrier nestlings or instead feed nestlings closest to the nest entrance. We used a balanced design to vary hungry and fed nestlings between the back and front of the nest box. We deprived half of the nestlings in each brood of food for an hour, and then, each nestling was constrained using Plexiglas dividers to a quadrant in the nest box. We videotaped inside the box to assess begging intensity and food delivery to individual nestlings. Hungry nestlings begged more intensely and received more food than fed nestlings, regardless of their proximity to the nest entrance. However, when delivering the first feed to nestlings, parents favored front nestlings over hungry nestlings, possibly due to a bias resulting from the manipulation, which involved replacing and rearranging nestlings after a 1-h period. Overall, parents did not favor nestlings in the front of the nest over those in the back. Parents therefore are able to distinguish hungrier nestlings and preferentially feed them under favorable environmental conditions, when brood reduction is uncommon. Significance statement When parents choose which offspring to feed, they may assess begging signals, which can include movements and vocalizations that vary in intensity. Alternatively, cavity-nesting species may use simple rules such as favoring offspring that have pushed to the front of the nest. We conducted an experiment to determine whether western bluebird (Sialia mexicana) parents would preferentially feed hungry nestlings over fed nestlings when Plexiglas dividers prevented competition and equalized the frequency with which hungry and fed nestlings were in the front versus back of the nest. After depriving half of each brood of food for an hour, we measured begging intensity and food delivery. Parents preferentially fed hungrier nestlings, which begged more intensely, regardless of their position in the nest, indicating that parents are able to distinguish between hungry and fed nestlings.

Eavesdropping and cue denial in avian acoustic signals

Article

Aug 2016

Although some signals seem adapted to maximize transmission of cues to intended receivers, others appear to have been selected to deny specific types of cues to unwanted receivers. We review three categories of avian vocal signals that have been suggested to show adaptation for cue denial: aerial predator alarm calls, begging calls, and soft songs and calls. Evidence supports the conclusion that aerial alarm calls are adapted to deny localization cues and that begging calls and soft songs are adapted to deny detection. Selection for denial of cues in acoustic signals has also been documented in a variety of other animals. In summary, eavesdropping by unwanted receivers is often as important in shaping the structure of acoustic signals as is selection for transmission to intended receivers.

Post-fledging survival of altricial birds: Ecological determinants and adaptation

Article

Full-text available

Jul 2016
J FIELD ORNITHOL

For altricial young, fledging is an abrupt step into an unknown environment. Despite increasing numbers of studies addressing the post-fledging period, our current knowledge of the causes and consequences of post-fledging survival remains fragmentary. Here, we review the literature on post-fledging survival of juvenile altricial birds, addressing the following main questions: Is low post-fledging survival a bottleneck in the altricial reproductive cycle? What is known of proximate and ultimate causal factors such as trophic relations (food and predation), habitat conditions, or abiotic factors acting in the post-fledging period? We analyzed weekly survival estimates from 123 data series based on studies of 65 species, covering weeks 1–13 post-fledging. As a general pattern, survival of fledglings was low during the first week post-fledging (median rate = 0.83), and improved rapidly with time post-fledging (week 4 median rate = 0.96). For ground-nesting species, survival immediately after leaving nests was similar to egg-to-fledging survival. For species breeding above-ground, survival during the first week post-fledging was substantially lower than during both the nestling period and later post-fledging stages. Thus, the early post-fledging period is a bottleneck of markedly elevated mortality for most altricial species. Predation was the main proximate cause of mortality. Various factors such as habitat, annual and seasonal variation in the environment, and the physical condition of fledglings have been found to affect post-fledging survival. Individual survival depended strongly on physical traits such as mass and wing length, which likely influence the ability of fledglings to escape predation. Trophic relationships at various levels are the main ultimate driver of adaptation of traits relevant to survival during the pre- and post-fledging periods. Spatiotemporal dynamics of food resources determine the physical development of juveniles and, in turn, their performance after fledging. However, predators can cause quick and efficient selection for fledgling traits and adult breeding decisions. Parental strategies related to clutch size and timing of breeding, and the age and developmental stage at which young fledge have substantial effects on post-fledging survival. The intensity and duration of post-fledging parental investment also influences fledgling survival. Post-fledging mortality is therefore not a random and inevitable loss. Traits and strategies related to fledging and the post-fledging stage create large fitness differentials and, therefore, are integral, yet poorly understood, parts of the altricial reproductive strategy. Para juveniles altriciales, salir del nido es un paso abrupto hacia un ambiente desconocido. A pesar del incremento en los estudios investigando el periodo posterior a la salida, nuestro conocimiento actual de las causas y consecuencias de la supervivencia luego de salir del nido es fragmentada. Aquí, revisamos la literatura sobre la supervivencia de aves juveniles altriciales posterior a su salida del nido, con el fin de responder las siguientes preguntas principales: es la baja supervivencia luego de salir del nido un cuello de botella en el ciclo reproductivo altricial? Que sabemos sobre los factores causales últimos y proximales, como las relaciones tróficas (comida y depredación), condiciones del hábitat o factores abióticos que influencian el periodo posterior a la salida del nido? Analizamos estimados semanales de supervivencia de 123 series de datos basados en estudios de 65 especies, cubriendo 1–13 semanas posteriores a la salida del nido. Como patrón general, la supervivencia de los volantones fue baja durante la primera semana posterior a la salida (mediana de la tasa = 0.83) y mejoro rápidamente con el tiempo luego de la salida (semana 4 mediana mediana de la tasa = 0.96). Para especies que anidan en el suelo, la supervivencia inmediatamente después de salir del nido fue similar a la supervivencia de huevo a volantón. Para especies que anidan por encima del suelo, supervivencia durante la primera semana posterior a la salida fue substancialmente menor que durante los periodos de anidación y periodos tardíos posteriores a la salida. Consecuentemente, el periodo temprano posterior a la salida del nido es un cuello de botella con una marcada mortalidad elevada para la mayoría de especies altriciales. Depredación fue la principal causa proximal de mortalidad. El hábitat, variación anual y estacional del ambiente y la condición de los volantones han sido reportados como factores que afectan la supervivencia posterior a la salida del nido. La supervivencia individual dependió fuertemente de caracteres físicos como masa, longitud del ala, los cuales probablemente influencian la habilidad de los volantones de escapar a los depredadores. Relaciones tróficas en varios niveles son el factor ultimo de adaptación de caracteres relevantes para la supervivencia durante los periodos previos y posteriores a la salida del nido. La dinámica espacio-temporal de los recursos alimenticios determinan el desarrollo físico de los juveniles y por lo tanto su rendimiento después de salir del nido. Sin embargo, los depredadores pueden causar selección rápida y eficiente para los caracteres de los volantones y de las decisiones de reproducción en los adultos. La intensidad y la duración de la inversión parental posterior a la salida del nido también influencia la supervivencia de los volantones. La mortalidad posterior a la salida del nido es por lo tanto no aleatoria y una perdida inevitable. Los caracteres y las estrategias relacionadas con la salida del nido y la etapa posterior a esta salida, crean diferencias grandes en la aptitud y por lo tanto son una parte integral pero poco comprendida de la estrategia de reproducción altricial.

Nest-dwelling ectoparasites reduce begging effort in Pied Flycatcher (Ficedula hypoleuca) nestlings

Article

Jun 2016
IBIS

Corticosterone triggers high-pitched nestlings' begging calls and affects parental behavior in the wild zebra finch

Article

Jun 2016
BEHAV ECOL

Nestlings beg to parents to communicate their need. Nevertheless, the specific signal driving parental care remains only partially understood. No study to date has been able to link a specific change in the physiological state of the young with, on the one hand, the modulation of a precise component of its begging behavior and, on the other hand, a direct modification of parental behavior reflecting an adjustment to an appropriate level of care. Here we orally administrated either exogenous corticosterone or a peanut oil control to free-living zebra finch nestlings and recorded begging behavior directly after treatment. Using a continuous automated monitoring system to record parental behavior in the wild, we simultaneously monitored the rate and duration of parental nest visits and foraging behavior at artificial feeders during 6 days posttreatment. We show that corticosterone modified the begging calls’ spectrum. Parents of corticosterone-treated broods spent more time in the nest and in feeders, and their older nestlings gained more body mass. Begging calls thus show a corticosterone-driven flexibility, which may inform parents of nestlings’ physiological state and allow them to provide an appropriate level of care.

Effects of variation in nestling hunger levels and begging on the provisioning behavior of male and female Eastern Phoebes ( Sayornis phoebe )

Article

Full-text available

Mar 2016

Nestling birds solicit food from their parents using conspicuous vocalizations and visual begging displays, and evidence suggests begging represents an honest signal of need that adults use to determine provisioning rates. Less is known about how adult males and females may differ in response to changes in nestling begging behavior as a result of variation in hunger levels or how nestling begging and adult provisioning may vary seasonally in multi-brooded species. To examine these parent-offspring interactions, we manipulated hunger levels of nestling Eastern Phoebes (Sayornis phoebe) during the 2011 breeding season in central Kentucky. Both first and second broods were divided into three treatments: whole brood fed (n = 12), whole brood deprived (n = 16), and some fed/some deprived (split; n = 14). Food-deprived nestlings begged with increased intensity, and fed broods begged with less intensity. Adult Eastern Phoebes adjusted their provisioning rates accordingly, provisioning food-deprived nestlings at higher rates than fed and split broods. These results suggest that nestling begging is an honest signal of hunger and parents respond to variation in nestling begging by adjusting their provisioning behavior. Provisioning rates of male and female phoebes did not differ, but post-treatment responses of adults differed for first and second broods. For both first and second broods, adults reduced provisioning rates to nestlings in fed and split broods. However, food-deprived nestlings in first broods were fed at similar rates before and after treatment, whereas food-deprived nestlings in second broods were provisioned at much higher rates after treatment. Differences in the provisioning of first and second broods may represent a trade-off between investment in current and future reproduction.

Pied Flycatcher nestlings incur immunological but not growth begging costs

Article

Full-text available

Apr 2016
BEHAV ECOL

Many theoretical models on the evolution of nestling begging assume this behavior is costly, so that only nestlings in real need of food would profit from giving intensive signals to parents. However, evidence accumulated for the last 2 decades is either contradictory (growth costs) or scant (immunological cost). Here, we experimentally test the existence of both costs in pied flycatcher (Ficedula hypoleuca) nestlings, a species in which parents appropriately respond to honest begging signals. Nestlings were paired by nest of origin and similar body mass. In each pair, a nestling was forced to beg for 51 s/meal, whereas the other begged for only 3.4 s/meal, both receiving the same amount of food. Simultaneously, the nestling immune response to an antigen (phytohemagglutinin) was measured. Experimental nestlings showed reduced immunocompetence compared with control chicks, which in this species could be regarded as a genuine direct cost. High-begging nestlings also gained less mass during the daylight activity hours. However, they lost less mass while resting at night, resulting in similar mass gains for both groups across the whole daily cycle. This suggests that negative effects of excess begging on mass gain can be compensated for by nestlings, thus avoiding the negative fitness consequences (i.e., cost) of a retarded growth. Mixed results found in previous studies may reflect interspecific differences in compensatory changes in mass gain. But if such differences do not map into fitness consequences, they may be of little help to answer the question of whether begging entails direct growth costs.

Oxidative Stress in Early Life: Associations with Sex, Rearing Conditions, and Parental Physiological Traits in Nestling Pied Flycatchers

Article

Feb 2016

Conditions experienced during early development can affect the fitness of an organism. During early life, oxidative stress levels can be particularly high due to the increased metabolism and the relatively immature antioxidant system of the individual, and this may have medium- and long-term fitness consequences. Here we explore variations between levels of oxidative stress measured during early life in relation to sex, breeding conditions (hatching date and brood size) and parental condition and levels of oxidative markers in a wild population of the Pied Flycatcher (Ficedula hypoleuca) followed during two years. A marker of total antioxidant capacity (TAS) in plasma and total levels of glutathione (GSH) in red blood cells as well as a marker of oxidative damage in plasma lipids (malondialdehyde, MDA) were assessed simultaneously. Our results showed that nestling total GSH levels were associated with parental oxidative status, correlating negatively with maternal MDA and positively with total GSH levels of both parents with a high estimated heritability. This suggests that parental physiology and genes could be determinant for endogenous components of antioxidant system of the offspring. Moreover, we found that total GSH levels were higher in female than in male nestlings, and that hatching date was positively associated with antioxidant defences (higher TAS and total GSH levels).These results suggest that different components of the oxidative balance are a variety of environmental and intrinsic influencing factors. Future experimental studies must disentangle the relative contribution each of these on nestling oxidative status, and how the resulting oxidative stress at early phases shape adult phenotype and fitness.

Maternal effects and life history trade-offs in a cooperative breeder, the sociable weaver (Philetairus socius)

Thesis

Full-text available

Dec 2013

Matthieu Paquet

Maximizing of the number copies of genes that are transmitted to the next generations involves a series of tradeoffs. In cooperatively breeding species some sexually mature individuals do not breed but instead help other individuals to raise their offspring. These helpers are particularly interesting in a life history context as they create a predictably favorable breeding environment and their presence can thus influence evolutionary trade-offs. A major evolutionary trade-off that is often neglected in studies on cooperative breeding is maternal allocation, notably through maternal effects that are epigenetic modifications of offspring phenotype. Here we investigate whether there are maternal effects induced by the presence of helpers and their possible consequences on females and their offspring in a colonial cooperative breeder of southern Africa, the sociable weaver Philetairus socius. Our results show that females lay smaller eggs in the presence of helpers and in addition these eggs have lower corticosterone and testosterone concentrations. Our results also show a higher survival probability of females breeding in groups, which may be partially due to their lower investment in eggs. In addition, a study of roosting chamber temperatures in relation to group size suggests further benefits for parents and helpers, particularly through lower costs of thermoregulation that could also allow energy savings for survival. To start understanding the consequences of helpers presence and differential maternal allocation for offspring we conducted a cross fostering experiment. Our results show that eggs produced by females breeding in larger groups produce chicks that beg at a lower rate, showing that maternal effects may influence chicks’ behavior. Finally, we investigated post-fledging survival through capture-recapture analyses and, surprisingly, found that fledglings have a lower survival probability when raised with helpers. Taken together, these results demonstrate the importance of studying maternal effects on cooperative breeders and open several research prospects on family conflicts and life history trade-offs according to the presence of helpers.

COSTS AND BENEFITS OF COOPERATIVE INFANT CARE IN WILD GOLDEN LION TAMARINS (LEONTOPITHECUS ROSALIA)

Article

Jan 2009

Jennifer Siani

High begging intensity of great spotted cuckoo nestlings favours larger-size crow nest mates

Article

Full-text available

Jun 2015

In nests of birds parasitized by a larger non-evicting brood parasite, host chicks typically are at disadvantage in competing for food and often starve. However, when host chicks are larger, they may benefit from the presence of the parasite, which contributes to the net brood begging signal but cannot monopolize the food brought to the nest. Here, we show that, despite a higher begging intensity, great spotted cuckoos (Clamator glandarius) did not outcompete larger size carrion crow (Corvus corone corone) nestlings. Furthermore, cuckoos’ exaggerated begging allowed crow nest mates to decrease their begging intensity without negative consequences on food intake. Assuming an energetic cost to chicks of begging intensely, our results suggest that crow chicks sharing the nest with a cuckoo may obtain an advantage that should be weighed against the loss of indirect fitness due to parasitism.

A cross-fostering experiment reveals that prenatal environment affects begging behaviour in a cooperative breeder

Article

Apr 2015

Prenatal breeding conditions have broad influences on maternal allocation to reproduction which can strongly affect future begging behaviours of offspring. The social environment is part of the prenatal environment; however, its influence on maternal allocation has been poorly investigated and experimental tests linking prenatal conditions to begging behaviour have seldom been conducted. In cooperative breeders the presence of additional carers, the helpers, generally predicts an increase in provisioning during the nestling stage. Since begging is costly, in these species producing offspring that beg less in the presence of helpers may be a way of saving energy not only for the offspring but also for the future survival and reproduction of females. To date, whether mothers may manipulate begging behaviour in relation to helper presence is unstudied. We conducted a cross-fostering experiment in a cooperatively breeding bird, the sociable weaver, Philetairus socius, to disentangle the possible effects of prenatal and postnatal environments on begging behaviour. Pre- and postnatal environments correspond here to the number of carers in the nest of origin and the foster nest, respectively. As predicted, begging was influenced by the prenatal environment, with nestlings originally from larger groups begging less. In addition, chicks fed by more foster birds also begged at a lower rate. We conclude that the prenatal environment influences begging behaviour. This result has important implications for understanding cooperative breeding strategies since producing offspring that beg less with more helpers may allow energy savings for females and related offspring and helpers.

Intensity of mouth colouration in blackcap nestlings affects food distribution among siblings but not provisioning of the whole brood

Article

Full-text available

Sep 2012
IBIS

Ewa Wegrzyn

Among various begging stimuli, mouth coloration has received increasing attention in recent years, and previous research has demonstrated that mouths of nestling Canaries Serinus canaria get redder with the extent of food deprivation and that parents preferentially feed nestlings of redder gapes. This study assesses whether the intensity of red mouth colour in nestling Blackcaps Sylvia atricapilla is a signal in parent–offspring communication. This is one of the few species with a naturally red gape in which the function of mouth redness has been tested. Three predictions were experimentally tested: (1) reddening the gape of a single nestling within a brood increases its provisioning in relation to other siblings; (2) reddening the gapes of all nestlings within a brood increases parental feeding rate; and (3) food deprivation increases nestling mouth redness. The effect of nestling quality on mouth redness was also assessed. The intensity of gape coloration affected food distribution, but in a way opposite to that expected: an increase in mouth redness of the nestling caused reduced feeding by parents. However, reddening the gapes of all nestlings had no effect on provisioning of the whole brood, suggesting that Blackcap parents use different cues for provisioning particular nestlings and the whole brood. Intensity of mouth redness in Blackcap nestlings was not affected either by food deprivation or by nestling quality in terms of mass and rank in the nest.

Intensity of mouth coloration in Blackcap Sylvia atricapilla nestlings affects food distribution among siblings but not provisioning of the whole brood

Article

Full-text available

Jan 2013

Factors Affecting Vocalization in Tengmalm's Owl (Aegolius funereus) Fledglings during Post-Fledging Dependence Period: Scramble Competition or Honest Signalling of Need?

Article

Full-text available

Apr 2014
PLOS ONE

Begging behaviour of nestlings has been intensively studied for several decades as a key component of parent-offspring conflict. There are essentially two main theories to account for intensity of food solicitation among offspring: that intensity of begging is related to some form of scramble competition between nest mates or that it offers honest signalling of need to parents. The vast majority of studies which have addressed begging behaviour have been based on observations of, and experiments on, nestlings and have not considered begging behaviour, during the post-fledging period. Begging vocalizations in this post-fledging phase of dependence have rarely been studied, despite the importance of vocalizations as a communication method between offspring and parents, particularly for nocturnal species. We radiotracked 39 fledglings of the Tengmalm's owl (Aegolius funereus) in two years with different availability of prey: 2010 (n = 29 fledglings) and 2011 (n = 10 fledglings) and made 1320 nightly localizations in which we recorded presence or absence of begging calls. Within years, the most important measures related to the probability of vocalization were body condition at fledging, time of night, number of surviving siblings, age and weather conditions. Begging intensity increased with age in both years; however, in the year with low prey availability fledglings vocalized significantly more often. The main factor causing these differences between years was probably the different availability of prey, affecting breeding success, post-fledging behaviour, and thus also both short- and long-term needs of offspring. We believe that our results suggest honest signalling of their fledgling's need.

Effect of alarm calling by male Red-winged Blackbirds on nestling begging and female provisioning behavior

Article

Dec 2011
J FIELD ORNITHOL

Nestling begging and parental provisioning can attract nest predators and reduce reproductive success, so parents and their offspring might be expected to respond adaptively by minimizing predator-attracting cues when predators threaten nests. Male Red-winged Blackbirds (Agelaius phoeniceus) are well known for their antipredator alarm calls that contain information about the approach of potential nest predators. We examined the begging behavior of nestlings and the provisioning behavior of females in response to antipredator alarm calls of males to test the adaptive response hypothesis. Playback experiments provided no evidence that alarm calls function to switch off vocal begging; nestlings were equally likely to beg vocally during playback and control periods. Video recordings showed that male alarm calling had no significant effect on inappropriate vocal begging (in the absence of an adult), but significantly reduced the incidence of spontaneous calling (in the absence of begging). Adult females responded to male antipredator alarm calls by delaying their provisioning visits. In addition, although having no significant effect on use of nest-arriving calls by females, male alarm calling significantly reduced their use of nest-leaving calls. We conclude that nestling and female Red-winged Blackbirds respond to male alarm calls in ways that might reduce the risk of predation, but nestlings beg vocally when females arrive to feed them, regardless of male alarm calling, perhaps to avoid a competitive disadvantage with broodmates.

Metabolic Costs and Honest Signalling of Need during the Development of Endothermy in American White

Article

Sex disparity in COVID-19 infection and mortality

Article

Full-text available

Jun 2020

The outbreak of Covid-19 is caused by a severe acute respiratory syndrome novel coronavirus 2 (SARS-CoV-2) that was officially reported in China at the end of December 2019, and is now spread across more than 180 countries worldwide. The source of this virus is not very clear; however, many research investigations speculated its origin from an unknown animal to humans. The sweep of viral infection is too high and the number of infected people is doubled every 3-10 days worldwide in the initial 6 months. Early data on Covid-19 suggests a higher infection and mortality rate among males as compared to females. In worldwide data analysis, we found that among European nations, viral infection in females is equal to or more than males, whereas in India, it is approximately thrice among males. When it comes to Covid-19 mortality, males are more susceptible than females across all regions with a few exceptions. In this article, we have discussed likely reasons for sex disparity in Covid-19 infection and mortality with a focus on India.

Diversity of the bacterial community and secondary sexual characters in the peacock

Thesis

Apr 2017

Haider AL-Murayati

Bird feathers harbour numerous microorganisms that could be acquired from the surrounding environment, these microorganisms may exert intense selection on their hosts by reducing fecundity and survivorship. Several bacterial taxa that live on feathers have the ability to degrade feather keratin and cause damage to feather structure and may alter the feather colouration. Birds use visual signals such as bright colours or exaggerated ornamentation for socio-sexual communication as well as species recognition. Only healthy individuals are able to produce exaggerated secondary sexual characters and still remain resistant to debilitating parasites. Peacocks (Pavo cristatus) is a polygamous species that have different exaggerated ornamentation, the most notable secondary sexual characters of the peacock are their long-decorated trains that comprise the magnificent ocelli which contain three different iridescent colours. Through a culture based technique we isolate feather bacterial community from differently coloured parts of the ocelli of the peacock’s train. The study reveals that there was a heterogeneous distribution of bacteria among the differently coloured parts of ocelli. The abundance and prevalence of specific bacterial taxa was related to the degree of feather degradation, expression of different secondary sexual character, changes in ocelli colouration and daily growth increment. Furthermore, we found a small effect of the expression of secondary sexual characters on biasing of brood sex ratio towards production of more sons than daughters. The work presented in this thesis provide evidence that feather ocelli may consider as a reliable signal of the diversity and the abundance of bacteria in peacock and in consequence indication for the individual quality and that allowing the choosy females to pick males with a specific bacterial community.

Surprising flexibility in parental care revealed by experimental changes in offspring demand

Article

Dec 2016

Parental behaviour often exhibits plasticity to factors expected to affect the benefits or costs of care. For example, parent songbirds typically increase their provisioning behaviour as nestlings mature. Several mechanisms exist that could allow parents to track nestling age and provide appropriate care. We performed a short-term experiment on house sparrows, Passer domesticus, in which offspring of different ages were exchanged to assess the level of flexibility parents exhibit and the likely cues they use. We found that a pair's rate of food delivery, an individual parent's visit rate to the nest, the duration of a foraging trip, and both the time a parent was in the nest and how long they perched near the nest after emerging from feeding nestlings changed according to the age of the offspring at the time. This shift in parenting was evident by the second visit after the swap. The amount of food brought per trip did not change with either natural or manipulated age. While females spent more time in the nest than males, there were no sex differences in the responses to the experiment. Food delivery rate increased nestling mass gain during each phase of the experiment, suggesting that parental plasticity in delivery was beneficial to offspring. However, there was an additional effect of the experiment on nestling weight gain, suggesting possible effects of food type brought during each phase of the experiment. Parent sparrows appear to use cues of offspring age over a time span that differs greatly from the natural time course of changes in nestling demand. This extension of plasticity into unnatural conditions has implications for understanding individual differences in plasticity and how at least some organisms might adjust to rapid and unusual environmental change.

Starving honey bee (Apis mellifera) larvae signal pheromonally to worker bees.

Article

Full-text available

Feb 2016

Starving honey bee (Apis mellifera) larvae signal pheromonally to worker bees.

Article

Feb 2016

Zhi-Jiang Zeng

Starving honey bee (Apis mellifera) larvae signal pheromonally to worker bees

Article

Full-text available

Feb 2016

Cooperative brood care is diagnostic of animal societies. This is particularly true for the advanced social insects, and the honey bee is the best understood of the insect societies. A brood pheromone signaling the presence of larvae in a bee colony has been characterised and well studied, but here we explored whether honey bee larvae actively signal their food needs pheromonally to workers. We show that starving honey bee larvae signal to workers via increased production of the volatile pheromone E-β-ocimene. Analysis of volatile pheromones produced by food-deprived and fed larvae with gas chromatography-mass spectrometry showed that starving larvae produced more E-β-ocimene. Behavioural analyses showed that adding E-β-ocimene to empty cells increased the number of worker visits to those cells, and similarly adding E-β-ocimene to larvae increased worker visitation rate to the larvae. RNA-seq and qRT-PCR analysis identified 3 genes in the E-β-ocimene biosynthetic pathway that were upregulated in larvae following 30 minutes of starvation, and these genes also upregulated in 2-day old larvae compared to 4-day old larvae (2-day old larvae produce the most E-β-ocimene). This identifies a pheromonal mechanism by which brood can beg for food from workers to influence the allocation of resources within the colony.

A trade-off between predation risk and sibling competition in the begging behavior of Coal and Great Tits

Article

Oct 2005
J FIELD ORNITHOL

Gregorio Moreno-Rueda

Sibling competition selects nestlings to beg as quickly as possible when a stimulus in the nest entrance is presented. However, predation risk may select for nestlings to properly assess stimuli before begging, because nestlings that beg to erroneous stimuli may signal their position to a predator. The begging behavior of Coal Tit (Parus ater) and Great Tit (Parus major) nestlings to an artificial stimulus imitating a predator was examined. Sightless nestlings begged to the stimulus, but older nestlings did not. Developmental improvement of the sentient capacity, especially the acquisition of vision, might explain results of this study.

Current Ornithology

Chapter

Full-text available

Jan 1995

In most animals, offspring from a reproductive bout usually hatch, emerge, or are born within a relatively short time of each other compared to the time required for their development. Thus, hatching or birthing in most animals is synchronous. This is especially likely to be true for animals with internal fertilization and development, where the birth of alll offspring occurs simultaneously (e.g., some fihes, snakes, and most mammals). Synchronous reproduction also occurs in animals with external fertilization or development when all zygotes are subject to the same environmental conditions (e.g., many insects, anurans, and fishes). Thus, in most the behavior of parents has little effect on the time between the emergence of their first and last young.

The Role of Energetic Costs in the Evolution of Begging Behavior of Nestling Passerines

Article

Jan 1997

John P. McCarty

A Review of Parent-Offspring Conflict and Brood Reduction in the Pelecaniformes

Article

Full-text available

Jan 1987

Hugh Drummond

According to Trivers' (1974) theory of parent-offspring conflict, sexual reproductive leads to a fundamental asymmetry in the reproductive interests of parents and their offspring, which should generate conflict between them. Because the behavior of some pelecaniformes has been cited in support of the theory, information on the six families comprising the order was reviewed to test the theory provisionally and to identify areas where further research is needed. Information on tropicbirds and frigatebirds is insufficient to reach conclusions, but studies of pelicans, boobies, cormorants, and anhingas (suborder Pelecani) supported some predictions and failed to support others. Parent-offspring conflict over distribution of food among contemporary sibs is supported by offspring behavior and to some degree by parental behavior. Brood reduction appears to be common in all four families in species laying multiple-egg clutches, but there is no clear evidence of the predicted conflict between parents and senior offspring over elimination of the junior chick, whether chick loss is facultative or obligate; rather, parent-offspring cooperation is indicated. Parent-offspring conflict over distribution of food between successive broods is supported by observations of parental and offspring behavior in pelicans, boobies, and cormorants. Lack of behavioral conflict could reflect an evolutionary solution to underlying conflict of interests or, alternatively, congruence of those interests; and behavior consistent with predictions is susceptible to alternative explanations. Problem-oriented studies including behavioral description and analysis of fitness benefits are needed to clarify these issues. /// Segun la teoría de conflicto padre-hijo de Trivers (1974), la reproducción sexual conduce a una asimetría fundamental en los intereses reproductivos de los padres y sus crias, la cual debería de generar conflicto entre ellos. Dado que la conducta de algunos pelecaniformes ha sido citada en apoyo a la teoria, se hizo un resumen de la información sobre las seis familias que integran el orden para ponerla a prueba e identificar a las areas donde se requiere de mas investigación. La información que se tiene sobre las aves del trópico y sobre las fragatas no es suficiente para llegar a conclusiones, pero los estudios de los pelícanos, los bobos, los cormoranes y los ahuizotls (el suborden Pelecani) dan apoyo a algunas predicciones mas no a otras. Conflicto padre-hijo sobre la distribución del alimento entre hermanos comtemporaneos esta apoyado por la conducta de las crias y en cierto grado por la conducta de los padres. La reducción de la nidada parece ser común en las cuatro familias en las especies que ponen nidadas de varios huevos, pero no hay evidencias claras del predicho conflicto entre los padres y la cria mayor sobre la eliminación de la cria menor, ni cuando la perdida de crias en facultativa ni cuando es obligada; mas bien, la cooperación padre-hijo esta señalada. Conflicto padre-jijo sobre la distribucion del alimento entre nidadas sucesivas está apoyado por las observaciones de la conducta de los padres y las crias en los pelícanos, los bobos y los cormoranes. La falta del conflicto conductual podria reflejar una solución evolutiva al conflicto subyacente de intereses o, alternativamente, la congruencia entre dichos intereses; y la conducta que es consistente con las predicciones es suceptible a las explicaciones alternativas. Se requieren de estudios enfocados en problemas específicos que incluyan a la descripción conductual y el análisis de los beneficios en términos de la adecuación, para aclarar estos puntos.

Elicitation of Vocalizations and Pecking in Ring-Billed Gull Chicks

Article

Full-text available

Jan 1981
BEHAVIOUR

Laboratory experiments were conducted on ring-billed gull chicks to ascertain the effect of different stimuli on the frequency of peer and distress calling or pecking at visual objects. Hungry chicks pecked more and gave more peer calls than satiated chicks but fewer distress calls. Cold, a sudden noise, and pain produced an increase in distress calling but a decrease in peer calling. Conversely, increased warmth and pressure on a chick's back- stimuli associated with brooding - produced the opposite effect. Presentation of visual models, especially those resembling gulls, resulted in an increase in pecking and peer calling and a decrease in distress calling. Models with small visual features were effective in eliciting pecks but not peer calls. The playback of different parental calls had little effect on the response tendencies of either hand-reared or parent-reared chicks although parent-reared chicks emitted fewer distress calls during the alert call playback than during any of the other calls. These results support the hypothesis that in the ring-billed gull, the distress call is a request for general aid and is given when a chick is in physical discomfort or out of visual contact with its parent whereas the peer call is a request for food and is given by hungry chicks, especially when stimuli indicate the parents' proximity to the chick.

Parent-Offspring Conflict

Article

Full-text available

Feb 1974
Am Zool

Robert Trivers

When parent-offspring relations in sexually reproducing species are viewed from the standpoint of the offspring as well as the parent, conflict is seen to be an expected feature of such relations. In particular, parent and offspring are expected to disagree over how long the period of parental investment should last, over the amount of parental investment that should be given, and over the altruistic and egoistic tendencies of the offspring as these tendencies affect other relatives. In addition, under certain conditions parents and offspring are expected to disagree over the preferred sex of the potential offspring. In general, parent-offspring conflict is expected to increase during the period of parental care, and offspring are expected to employ psychological weapons in order to compete with their parents. Detailed data on mother-offspring relations in mammals are consistent with the arguments presented. Conflict in some species, including the human species, is expected to extend to the adult reproductive role of the offspring: under certain conditions parents are expected to attempt to mold an offspring, against its better interests, into a permanent nonreproductive.

Parent-Offspring Conflict in Budgerigars

Article

Full-text available

Jan 1985
BEHAVIOUR

Melopsittacus undulatus clutches hatch extremely asynchronously, yet all nestlings grew at similar rates and fledged at similar sizes and ages. This independence of hatch order and performance seemed due primarily to the mother budgerigar's allofeeding strategy: females allofed offspring mainly on the basis of size, and only secondarily attended to begging rate. Offspring of a given age and size were treated the same by their mothers regardless of hatch order, and offspring undersized for their age were fed as if they were younger. In contrast, male budgerigars attended to offspring begging rates. Males tended to initiate feeding bouts when offspring begged, and to allofeed vigorous beggers more often. -from Authors

Begging Behavior in Budgerigars

Article

Full-text available

Jan 1989
ETHOLOGY

Five hypotheses about relationships between begging rates, feeding rates and other variables were investigated in captive budgerigar nestlings from 23 days post‐hatch to fledge date (Period 4). Within families, nestlings that begged more frequently during Period 4 were fed more often by their parents, but there was no indication that nestling weight on day 23 was related to begging rates in the subsequent growth interval. Instead, last‐hatched nestlings begged more than their older siblings. Last‐hatched nestlings were not “undersized” at the beginning of Period 4 relative to their siblings, and they experienced less competition than their siblings had at comparable ages. Even so, last‐hatched budgerigars begged more often, were fed more often and fledged at heavier weights than their older nestmates. Across families, there was a strong positive relationship between average Period 4 begging rate and average parental feeding rate, but this relationship was much weaker when brood sex ratio was taken into account: female‐biased broods had much higher begging and feeding rates than male‐biased broods. Brood size was related to begging, with higher ratios of begging to feeding rates for family members than for single nestlings. Taken together, these results suggest that relationships between feeding and begging behavior in budgerigars are more complex than theoretical models have suggested. More studies of avian begging and feeding patterns are required before we can generalize about the control of parental food allocations in birds.

A genetic analysis of parent-offspring conflict

Article

Full-text available

Dec 1978

1. When there is no cost to the selfish behavior, selection favors the spread of selfish alleles at offspring loci when the ratio of cost c to the parents' future offspring to benefit b to the selfish offspring is less than 2 for full-sibs and 4 for half-sibs. Selection on the parent favors offspring alleles where c/b1. For monogamous parents, parent-offspring conflict exists when b. 2. When performance of a selfish act involves a cost (), the relationship b no longer defines the conditions for the spread of selfish alleles. As increases, the upper limit of c/b decreases and the lower limit of b increases. 3. No conflict exists between parent and offspring over the best strategy to maximize reproductive success. When selfish alleles spread or when there is a cost to selfish behavior or parental counterstrategies, then RS is lowered for both parents and offspring. 4. The spread of selfish offspring alleles leads to a reduction in r and K. The spread of altruistic alleles leads to an increase in r and K. 5. Conflict exists between selfish offspring alleles and alleles at other independently assorting offspring loci. 6. In order to define the effects of an offspring behavior on its fitness, not only the ratio of cost to benefit but also the magnitude of b must be defined. Alleles with equal values of V, when V=b-0.5c, will not spread relative to one another. 7. Parent alleles that counteract offspring selfish alleles can spread as long as b. When the ratio c/bc/b>1.5, parent counteracting alleles spread faster than do offspring selfish alleles. 8. A number of factors, including the action of other offspring loci, parental counterstrategies, and the cost of selfish behavior will tend to favor the expression of selfish alleles with a low ratio c/b and a low to moderate magnitude of b. Selfish alleles with a high ratio c/b and a high benefit b should be relatively uncommon. 9. Winning parent-offspring conflict depends on the biological constraints of the situation, and is mainly determined by the relative costs of offspring selfish behavior and parental counteracting behavior.

Early stages of vocal ontogeny in the Magpie (Pica pica)

Article

Full-text available

Apr 1991

Tomas Redondo

The vocal repertoire of magpie (Pica pica) chicks consists of six calls: Begging Trill (BT), Soft Whistle (SW), Begging Scream (BS), Alarm Call (AC), Distress Call (DC) and Brief Contact Note (BCN). Both BT and SW have a tonal structure and their occurrence is restricted to the nestling period. At fledging, there is a gradual change from BT into BS and a sudden appearance of harsh calls similar to those of adult birds (AC, DC, BCN), without evident transitional forms with preceding tonal calls. Both the existence and the structural design of calls seem to be adapted for providing nestlings with immediate benefits linked to the two major chapters of allocation of parental care. Emission rates of BT increase with hunger motivation under laboratory conditions. Their structure suggests that they are easily located but liable to suffer from environmental degradation. BS of fledglings may be more resistant to degradation, a trait which may facilitate the identification by parents of their own offspring. Both AC and DC attract parents to defend the nest against potential predators, and their structure make them to be easily located and detectable at long distances. BCN are given by fledglings during bouts of locomotory activity (exploration and play) and they probably help in maintaining the cohesion of the group under conditions of poor visibility. In accordance, this call may be fairly located at short distances. The function of SW was unclear. It is given during periods of nestling inactivity between begging bouts, and could be easily elicited by tactile and auditory stimuli. After laboratory experiments, it is concluded that SW serve to indicate parents that nestlings are in good condition, hence to benefit from the parental willingness to invest in a brood with high prospects of survival. Since (i) there is a widespread lack of continuity in the development of adult vocalizations starting from nestling calls, and (ii) nestling calls seem to have evolved to provide birds with benefits in the short-term, these facts argue against the prevailing idea that the main function of calls early in ontogeny is to act as precursors of adult vocalizations.Das Lautrepertoire von Elsternestlingen besteht aus 6 Lautuerungen: Betteltrillern (BT), Sanftes Pfeifen (SP), Bettelkreischen (BK), Alarmruf (AR), Angstschreien (AS) und kurzer Kontaktruf (KR). BT und SP sind tonal und treten nur whrend der Nestlingsperiode auf. Zum Zeitpunkt des Ausfliegens geht BT graduell in BK ber und pltzlich treten auch ohne vorausgehende tonale bergangsformen rauhe Rufe hnlich denen der Altvgel auf (AR, AS, KR). Sowohl die Existenz als auch die Struktur der Lautuerungen scheinen als Anpassungen im Zusammenhang mit einer Optimierung der Brutpflege zu interpretieren zu sein. Die Emissionsrate von BT steigt unter Laborbedingungen mit der Hungermotivation. Die Struktur legt nahe, da BT leicht geortet werden kann, aber auch leicht von der Umgebung verschluckt wird. BS der flggen Jungen scheint davon weniger betroffen zu sein, so da die Eltern leichter ihre Jungen identifizieren knnen. AR und AS veranlassen die Altvgel, ihr Nest gegenber potentiellen Prdatoren zu verteidigen; die Struktur der Laute begnstigt ihre Ortung und Wahrnehmung ber grere Entfernungen. KR werden von den flggen Jungen bei lebhafter lokomotorischer Aktivitt (Exploration, Spiel) geuert; sie tragen vielleicht dazu bei, die Gruppe auch unter erschwerten optischen Kontaktmglichkeiten zusammenzuhalten. Die Funktion von SP blieb unklar. SP war whrend inaktiver Perioden zwischen Bettelverhalten zu hren und konnte leicht durch taktile und akustische Reize ausgelst werden. Nach Laborexperimenten ist zu schlieen, da SP den Eltern Wohlbefinden der Jungen anzeigt und so Bereitschaft zur Investition in eine Brut mit hoher berlebenswahrscheinlichkeit frdert. Da (1) zwischen den Rufen der Altvgel und dem Repertoire der Nestlingen weitgehend keine kontinuierlichen bergnge festzustellen und (2) Nestlingsrufe offensichtlich im Hinblick auf kuzfristige Gewinne zu interpretieren sind, spricht gegen die allgemein vorherrschende Ansicht, das Lautrepertoire in frhen Stadien der Ontogenie sei hauptschlich ein Vorlufer der Adultlaute.

Feeding chases in the Adélie penguin

Chapter

Jan 1978

David H. Thompson

Song sparrow 'rules' for feeding nestlings

Article

Jan 1981

J.R. Reed

Behavioural Ecology: An Evolutionary Approach

Article

Jan 1978

Was reizt den Trauerfliegenschnäpper (Muscicapa hypoleuca) zu füttern?

Article

Jan 1953

L. Von Haartman

The Life of Birds

Article

Jan 1976

Sensory Factors in the Behavioral Ontogeny of Altricial Birds

Chapter

Dec 1985
ADV STUD BEHAV

S.N. Khayutin

The chapter discusses the formation of feeding and defense behavior and the conditions eliciting them, as well as their interaction at all stages of nestling life, with features of the species' ecological environment. While analyzing these forms of behavior, special attention is paid to the dynamics of their sensory basis at the successive stages of early post-embroyonic development, to the maturation of sensory mechanisms, and the time of onset of their full-scale functioning— that is, to the intra- and inter-sensory heterochronics, enabling adaptation to the ecological environment of the species. The data presented in the chapter were collected during the past 10 years in the Oka-Terrace Reserve. The chapter is illustrated with experiments. The experiments were conducted in the laboratory but approximated natural conditions as much as possible: the nest was placed in the shielded nest-box with background noise and light levels equal to those in the wild. The nest temperature was automatically maintained constant. EMGs were recorded from the awake nestlings through wire electrodes implanted in their neck muscles. All electrophysiological data were obtained from the experiments with pied flycatchers. Sounds used for communication between nestlings and adult birds were analyzed with a Kay-Electric 7029A sonagraph.

Role of the Chick's Begging Behavior in the Regulation of Parental Feeding Behavior of Larus glaucescens

Article

Jan 1975

Bryan A. Henderson

Biostatistical Analysis (2nd ed.).

Article

Jun 1986

Parent-Offspring Interactions in Zebra Finches

Article

Jul 1978

The begging behavior of immature Zebra Finches has both visual and acoustic components. Begging nestlings gape at their parents, exposing characteristic mouth markings and a moving tongue. They also emit begging calls. Both components undergo changes as the offspring mature, and there is a shift from the visual to acoustic modality as the primary stimulus for feeding. Recorded fledgling begging calls were broadcast inside the cages of Zebra Finch parents with offspring. These begging calls stimulated parental feeding and other behaviors associated with feeding. The offspring also responded to recorded calls by showing begging behavior. Parents were sensitive to recorded begging calls from approximately day 16 to day 28 after the first offspring hatched, although there was substantial variation in these times among pairs of parents.

Begging Response in Nestling Red-winged Blackbirds (Agelaius phoeniceus): Effect of Body Temperature

Article

Sep 1990
Physiol Zool

Altricial birds are essentially ectothermic at hatching. Parental brooding is the primary thermoregulatory mechanism, and body temperature ( $T_{b}$ ) is about 5° C lower and more variable than adult $T_{b}$ . Thermoregulation improves with growth, and a stable $T_{b}$ near adult levels can soon be maintained. We hypothesize that the thermal performance curves for whole-animal behavior and for neuromuscular contractility should shift during development to match the normal $T_{b}$ range. We tested this hypothesis with 1- and 8-d-old nestling red-winged blackbirds (Agelaius phoeniceus). We measured several parameters of the begging display used to release parental feeding behavior at $T_{b}$ 's from 15° to 42° C. We also measured some of the isometric contractility properties of the sciatic-gastrocnemius system as a function of tissue temperature from 15° to 42° C. The optimal temperature for begging height, begging speed, gape width, and isometric tetanic force increased 5°-15° C between 1-d-old and 8-d-old birds. The temperature sensitivity ( $Q_{10}$ or $R_{10}$ ) of all variables except gape width also increased with age, resulting in a narrower range of near-optimal performance. The behavior parameters were more temperature-sensitive than the neuromuscular tetanic responses. The absolute performance of 8-d nestlings was better than that of 1-d nestlings except at low temperatures.

Female and Male Specialization in Parental Care and Its Consequences in Black-Billed Magpies

Article

Feb 1988

Deborah Buitron

The breeding biology of a small population of individually marked Black-billed Magpies (Pica pica) was studied from 1978 through 1981 in Wind Cave National Park, South Dakota. Mates cooperated extensively in nest building, defense of nest site, and care of eggs, nestlings, and fledglings. The two sexes specialized in different types of parental care, with the result that both parents were needed to fledge young. Of the types of parental care that I was able to measure, males contributed more than females to raising young and were also more active in expelling intruders and driving away predators. Feeding of young peaked the week after fledging and parental care continued for another 5 to 6 weeks. Indi- vidual variability in parental behavior and two cases of the care of young by unrelated adults are also discussed. Key words: Black-billed Magpies; Pica pica; parental care; individual variability.

The Handicap Principle in Parent-Offspring Conflict: Comparison of Optimality and Population-Genetic Analyses

Article

Feb 1991

The evolution of offspring handicap is studied in two ways. First, the problem is formulated in terms of a population game in which each player, parent and offspring, seeks to increase its own fitness. Second, we study the dynamics of an exact two-locus model in which one locus affects the behavior of offspring and the other affects that of parents. It is shown that the latter approach leads to a more complicated "game structure," in which parents maximize a weighted average number of offspring, with lower weight ascribed to the handicapped type. The weights depend on the rate of recombination. Under the assumption of fitness maximization, used in the game-theoretical approach, it is shown that a handicap always evolves. The two-locus analysis, however, produces a more realistic set of specific conditions for initial success and fixation of the handicap. When linkage is loose, these latter conditions coincide with a verbal prediction of Zahavi. With tight linkage, however, conditions for this evolution of offspring handicap are significantly restricted.

Supply and Demand in Tree Swallow Broods: A Model of Parent-Offspring Food-Provisioning Interactions in Birds

Article

Feb 1988

David J. T. Hussell

A supply-and-demand model was developed to describe parent-offspring food-provisioning interactions in nidicolous birds. The supply function represents the feeding response of the parents to the hunger signals of the brood, and the demand function describes the hunger-signaling response of the brood to the feeding rate. The intersection of the two functions is an equilibrium point representing the feeding rate and hunger-signaling level observed in the real world. The model was tested for broods of six tree swallows at 13 days of age. It was shown that the supply function shifts in response to changes in food abundance in the environment and that compensating shifts in the demand function occur in accordance with the nutritional condition of the young. The resulting feeding rates are relatively stable over wide ranges of food abundance and hunger-signal level, indicating that the behavioral system enables parents to adjust feeding rates to the needs of the young, in spite of variations in their environmen...

Models of parent-offspring conflict

Article

Jan 1985

Geoff A. Parker

Clutch Size, Fecundity and Parent-Offspring Conflict

Article

Apr 1991

Selection often acts in different ways on genes expressed in parents and offspring leading to parent-offspring conflict. The effect of parent-offspring conflict on the evolution of reproductive strategies is explored. Models are constructed using kin-selection techniques and it is argued that these are frequently more useful than techniques from classical population genetics. Parent and offspring optima are compared in models of (1) the trade-off between the number and size of offspring, (2) clutch size and (3) the evolution of reproductive effort with age structure. Parent-offspring conflict over clutch size is examined in more detail. Models of sibling competition are reviewed and it is suggested that the reduction in parental fitness caused by sibling competition may lead to selection on clutch size. The possibility that the parent may be selected to produce a hierarchy of sizes of young in order to reduce sibling conflict is investigated. The preliminary results give little support for this hypothesis. An extreme form of sibling conflict, siblicide, is also discussed. In some cases, the kin-selection approach fails in the analysis of siblicide and classical population genetic models are required. The paper concludes that parent-offspring conflict is a potentially significant, and often overlooked, factor influencing the evolution of reproductive strategies. Birds in their little nests agree And 'tis a shameful sight, When children of one family Fall out, and chide, and fight Isaac Watts, Love between Brothers & Sisters, 1721. Birds in their little nests agree With Chinamen, but not with me. Hilaire Belloc, On Food.

Clutch Size, Fecundity and Parent-Offspring Conflict: Discussion

Article

Apr 1991
PHILOS T R SOC B

The Occurrence, Context and Functional Significance of Aggressive Begging Behaviours in Young American White Pelicans

Article

Jan 1987
BEHAVIOUR

Aggressive behaviours occurring in association with about 90% of all feedings developed in American white pelican chicks approximately three weeks old. These behaviours involved aggression directed toward self (Convulstion) and other young (Aggression). Observation of feedings revealed that: (1) when both Convulsion and Aggression occurred before or after a given feeding, convulsion bore a closer temporal relationship to the feed itself than did Aggression, (2) the frequency of both Aggression and Convulsion prior to feeding increased as the length of the begging bout increased, (3) the frequency of Convulsion and Aggression following feeding was not related to the duration of the feed but did depend on the amount fed (as measured by throat distension). Observations of identifiable parents and chicks revealed that most chicks receive a single feeding each day, each parent returning to the colony every two days. The frequency of multiple feeds given to the same chick on the same day or (by the presumed same parent) two days later was not related to the frequency of Aggression or Convulsion given after a feeding. The close association of these displays with feeding and low-intensity begging suggests that they function primarily as begging displays or, for Aggression, to drive other young away from the parent food source. Evidence suggesting that Convulsion may be a manifestation of parent-offspring conflict is discussed. Alternative proposed functions of Convulsion and Aggression are not supported by data collected in this study.

The cost of honesty

Article

Aug 1977

Amotz Zahavi

Energy, Calling, and Selection

Article

Aug 1988
Am Zool

Michael Joseph Ryan

SYNOPSIS. Acoustic signals often mediate the mating process and are under selection through the action of female choice. Acoustic signalling requires relatively large amounts of energy input, but metabolic energy is coupled to acoustic energy inefficiently. Although not necessarily a cause and effect relationship, females often prefer signals with more energy. Females may prefer more intense calls, more complicated calls, or calls produced at a greater repetition rate. I discuss various evolutionary changes that could increase acoustic energy received by the female and examine how these changes are influenced by other factors inherent to communication systems: signal radiation, species recognition, sexual selection, the physiology of the receptor system, and environmental bioacoustics. I conclude that these factors constrain the ability of the animal to maximize energy received by the female. I then consider how two hypotheses, the good genes hypothesis and the runaway sexual selection hypothesis, attempt to explain the evolution of female choice for signals with greater energy content.

The Evolution of Begging: Sibling Competition and Parent-Offspring Conflict

Article

Jul 1986

Alan B. Harper

Two offspring traits are allowed to evolve: average (or typical) rate of begging and rate of change of begging intensity with changes in parental investment. Rate of change of parental investment with changes in begging intensity also can evolve. Chicks should vary their rate of begging in response to fluctuations in investment, and parents should respond to these changes so that any fluctuations in parental investment are compensated for on subsequent feeding trips. But the typical rate of begging can evolve to a high level as siblings compete for food from their parents. Typical begging intensity should vary with clutch size; the pattern of variation depends on whether the costs of begging are primarily the attraction of predators or are individual energetic costs. Species that raise just one chick at a time should show a low average begging intensity. -from Author

Parental Feeding Behaviour and Sibling Competition in the Pied Flycatcher Ficedula hypoleuca

Article

Nov 1987

Karin Gottlander

Parents almost exclusively fed the nestlings closest to them, but begging intensity also influenced a nestling's probability of receiving food. Probably because of the relatively slight weight spread among the nestlings, no difference in begging behaviour according to weight could be detected. Experimental heavier nestlings were, on average, significantly closer to the optimal position than in the natural situation. The nestlings tried to remain in the optimal position and had better chances to obtain 2 feeds in sequence during the experimental than during the unmanipulated period. Females tended to distribute food less evenly than males and to favour light nestlings; hence there may be a potential for parents to counteract sibling competition leading to an asymmetry of food allocation. A trade-off may exist between amount of time that can be spent identifying particular nestlings to feed and other activities.-from Author

Parental feeding rate in relation to begging behavior in assynchronously hatched broods of the great tit, emphParus major. An experimental study

Article

Jun 1983
BEHAV ECOL SOCIOBIOL

Variations in the begging behaviour of the nestlings of altricial birds can provide the parents with information about the nestlings' nutritional needs and thus influence the parental feeding rate. In a series of four experiments, the stimulus situation encountered by great tits on their feeding visits to the brood was manipulated to explore its effect on feeding rate.A higher feeding rate was observed under the following conditions: (1) after a period of food deprivation, as compared with both normal conditions and satiation through artificial feeding; (2) in periods when recorded begging calls were played during feeding visits, as compared with control periods; (3) after temporary removal from the nest of heavier, as compared with lighter, siblings. The lighter nestlings in the brood benefitted more —in terms of gain in weight — from the increase in parental feeding rate following the playing of begging calls than did the heavier nestlings. Differences in weight spread within broods did not affect the amount of food the parents brought.We conclude that parental feeding rate is affected not simply by the begging of the hungriest nestling, but rather by the behaviour of all the nestlings in the brood, which makes possible an adjustment of the feeding rate to the average hunger level of the brood. The effects of hatching asynchrony and sibling competition on parental feeding rate are discussed.

Honest signalling: The Philip Sidney game.

Article

Dec 1991

John Maynard Smith

Presents a model to illustrate A. Grafen's (1990) mathematical proof of A. Zahavi's (1981) argument that if a signal is to accurately represent the state of the sender, it must be costly. The model shows that honest signals must be costly if there is a conflict of interest between signaler and receiver, but cost-free signals can be honest if there is no such conflict. (PsycINFO Database Record (c) 2012 APA, all rights reserved)

The increase in risk of predation with begging activity in broods of Magpies Pica pica

Article

Jun 1992
IBIS

Begging activity in broods of Magpies Pica pica was measured as the average total number of begging nestlings and the number of nestlings giving begging calls between 5 and 9 days since the first nestling hatched. There was considerable between-brood variation in begging activity relative to day-to-day variation within broods. Predation between 7 and 20 days of age was more frequent among those broods which had not previously suffered from brood reduction due to nestling starvation. Broods which were preyed upon showed significantly higher levels of begging activity than broods of a comparable size that were not preyed upon. In addition, the time elapsed from hatching to predation showed a negative correlation with the total number of begging nestlings. Within broods, those nestlings with the highest begging motivation (measured as the latency to respond when stimulated) seemed to be more readily taken by predators. These results confirm the existence of costs associated to begging in the form of an enhanced risk of being detected by predators.

Selective resistance to approach: A precursor to fear responses to an alarm call in great tit nestlings Parus major

Article

Oct 2004
DEV PSYCHOBIOL

Olof O. Rydéan

The reactions of 10-day-old great tit nestlings to 3 auditory stimuli were studied. The stimuli, presented on a series of feeding occasions, were (1) the species' “seeet” alarm call, (2) a song strophe of the great tit, and (3) a song strophe of the tree-creeper (Certhia familiaris). In contrast to earlier findings in studies of older nestlings, these younger nestlings did not respond to the alarm call with cessation of begging. However, a significant differential effect of the alarm call was demonstrated when the conditioning rates for the nestlings' begging response to each of the 3 stimuli were determined. Thus, conditioning was significantly slower to the alarm call than to the other stimuli. The results agree with the general conception that responses to species-specific calls develop gradually during early ontogenesis. Thus fear responses to the alarm call, such as cessation of begging and “freezing,” which are elicited in newly fledged young, are preceded by weaker aversive tendencies that are not obvious from observations of the nestlings' behavior in nature. It is suggested that the nestlings' exposure to contrasting auditory stimulation–their own begging call and the parental feeding call–constitutes the experiential base for withdrawal responses to the “seeet” call.

Signalling of Need by Offspring to Their Parents

Article

Jul 1991
NATURE

Charles Godfray

THE young of birds and mammals often solicit food from their parents in ways that appear to be costly and to reduce their fitness1, 2. Thus birds in the nest beg vigorously for food, incurring energetic costs and possibly attracting predators3; the behaviour of young mammals requiring to suckle (bleating or crying, for example) similarly appears costly1, 2. If solicitation is a means by which the young communicate need to their parents, why has a less expensive form of communication not evolved4? An answer to this question is provided by the theory of parent-offspring conflict: natural selection acting on genes expressed in the young will lead to greater demands for parental resources than is optimal for the parent1, 5. The accurate communication of offspring need is evolutionarily unstable as offspring will be selected to demand extra resources. Models of parent-offspring conflict have shown that an evolutionarily stable equilibrium can exist at which an offspring solicits resources in a way that reduces its fitness, and a parent provides extra resources to prevent further expensive solicitation6-11. I present an alternative explanation for costly solicitation by showing that the level of offspring solicitation can be a true reflection of offspring need as long as solicitation is costly and the benefits of extra resources increase with need. My analysis suggests that the parent normally allocates resources using accurate information about the condition of the young. The requirement that the signalling system is costly is a direct consequence of the potential for parent-offspring conflict.

Development of Parent‐Young Interaction in Asynchronously Hatched Broods of Altricial Birds

Article

Jan 1981
ETHOLOGY

In bird species which have developed a brood reduction strategy, initial inequality among siblings is established through asynchronous hatching. After hatching, the maintenance of a weight hierarchy within the brood and its spread is governed by the allocation of feeds to the chicks and by the rate of parental feeding. In the present study, the initiation of parental feeding and subsequent changes in the feeding procedure were studied in asynchronously hatched broods of the great tit Parus major and the blackbird Turdus merula. During the period of hatching the brood was roused by a parental feeding call on most visits to the nest which made feeding more effective. Late-hatched young initially increased their chances to receive feeding offers by showing a high rate of spontaneous begging. In addition, they were more dependent than the older young on a high rate of mobility in order to be fed and they showed increasing mobility with age. Crucial changes in the feeding procedure took place at the end of the hatching period when the parents ceased to emit feeding calls and in the last few days before the abandonment of the nest when the biggest young started to jump towards the parents at feeding. These periods were identified as critical for late-hatched young. We argue that parental feeding rate is a feature of parent-young interaction that develops in order to adapt parental investment in individual nestlings to changes in food conditions when the brood is being raised.

Calling energetics of a neotropical treefrog, Hyla microcephala

Article

Jul 1989

We investigated the calling energetics of Hyla microcephala, a neotropical treefrog with an unusually complex vocal repertoire. Males respond to the calls of other individuals by adding secondary click notes to their calls, thereby increasing the total number of notes given per minute. Rates of oxygen consumption of males calling in metabolic chambers were 0.41–2.80 ml O2/(gh), corresponding to calling rates of 205–6330 notes/h. Note rate explained 95% of the variance in meta-bolic rate; the effect of variation in body size and temperature was small. Data from playback experiments with males in the field showed that note rate increased as as the number of notes in a stimulus call increased, and this resulted in substantial increases in the cost of calling. Average metabolic rates for males in the field were about 1.7 ml O2/(gh), for a net cost of calling of about 20 J/h for an average-size male. However, estimated metabolic rates varied by more than 300% and were strongly influenced by the proximity and calling activity of other males in the chorus. Male H. microcephala appear to conserve energy by reducing calling rates when only a few males are active and increasing calling efforts only when vocal competition among males is intense.

Nestling American robins compete with siblings by begging

Article

Nov 1991

The evolution of intense begging by dependent nestling birds has recently been the subject of several theoretical papers. The interesting problem here is that nestlings should be able to communicate their nutritional status to parents in ways that are less costly energetically and less likely to attract predators. Thus, conspicuous begging behaviour is thought to have evolved as a result of either competition among nestmates or the manipulation of their parents to provide more food than would otherwise be favoured by selection. We studied sibling competition for parental feedings in the American robin (Turdus migratorius). We demonstrate that the probability that an individual nestling received food was related to several indices of begging. When we experimentally prevented parents from feeding part of their brood, both the intensity of begging and the number of feedings subsequently received by food-deprived nestlings increased. Furthermore, the begging intensity of those nestlings that were not food-deprived also increased in response to the begging of their hungrier siblings.

Locatability of begging calls in nestling altricial birds

Article

Jun 1988

Nestling begging calls of altricial species of birds have design features (wide frequency range, abrupt onsets and modulation in amplitude and frequency) that make them easily located by birds and mammals, and so may attract predators to the nest. To be maintained by natural selection, such calls must also be beneficial. It is argued here that sibling competition for food during the early stages of nestling development favours locatability of begging calls, presumably because noisy nestlings attract the attention of parents. In the magpie, Pica pica, begging calls of nestlings have a wider frequency spectrum before the nestlings' eyes have opened, a trait that increases their locatability. A strategy of having locatable calls should spread if favoured by mechanisms that overcome the increased predation risk associated with such calls. Two mechanisms are proposed: increased attenuation of the signals by emphasizing higher frequencies (a feature commonly found in begging calls) and dispersion of energy over a wide time-frequency range, a trait that, because of sound degradation, probably masks the estimate of source distance by predators. This hypothesis agrees with predictions of models of intra-brood conflict: when predation costs are higher, level of solicitation (locatability) should decrease. Hole-nesting species, which have a lower risk of predation, have calls with wider frequency ranges and lower (less attenuable) medium frequencies than those of open-nesting species of a similar weight.

Shared and unshared parental investment, parent-offspring conflict and brood size

Article

Dec 1986

Taking as our starting point Trivers' (1974) account of parent-offspring conflict, we develop models of the influence of brood size on the optimal level of parental investment (PI) in the whole brood for parent and offspring, and on the magnitude of conflict between them. A modification of Trivers' model is proposed. In general, the benefit of an act of PI to an offspring in a brood of size N is (N+1)/N times the benefit to its parent. Therefore as brood size increases, offspring benefit approaches parental benefit, and this is because an increasing proportion of the offspring's benefit is being gained through siblings, to which offspring and parent are equally related. A distinction is drawn between ‘shared’ and ‘unshared’ types of PI. When PI is shared the total benefit accruing is not directly gained by all offspring but is shared amongst them (e.g. food brought to the young). In contrast, unshared PI can simultaneously benefit some or all of the brood (e.g. types of anti-predator defence). For shared investment, PI and conflict are predicted to increase with brood size. Two models of unshared anti-predator defence are described. If the predator characteristically takes the whole brood when it strikes (e.g. altricial nestlings) PI is predicted to increase and conflict decline with brood size, although this effect is inhibited or even reversed for high risk defence tactics because of the higher cost to larger broods if the parent dies. When the predator takes a single offspring (e.g. precocial birds) the parent's optimum PI is independent of brood size, the offspring's optimum PI declines in larger broods and conflict again declines with brood size. The parent is commonly expected to win the conflict over anti-predator care. Predictions concerning PI levels gain support from existing data, largely for birds, but evaluation of those for conflict must await the collection of new data. The distinction between shared and unshared investment is applicable to altruistic behaviour in general.

Sibling competition, parent-offspring conflict and clutch size

Article

Mar 1992

Population genetic models have shown that exploitation competition for resources between siblings can often lead to severe reductions in offspring fitness. As the parental optimum is normally the absence of competition, the presence of sibling competition is an aspect of parent-offspring conflict. Phenotypic techniques are developed for modelling sibling competition in broods where all members have equal competitive ability. Two forms of sibling competition are modelled, one suggested by competition between nestling birds, and the second suggested by competition between the larvae of gregarious insects. The phenotypic models confirm the genetic analysis and allow the study of the relationship between sibling competition and clutch size (the genetic models assumed infinite clutch size). Conflict may either increase or decrease with clutch size depending on how the costs of competition are spread among the members of the brood. It is also shown that in the presence of sibling competition, parents may be selected to produce smaller clutches than those that would be optimum in the absence of sibling competition.

The corruption of honest signalling. Anim Behav 41: 865-873

Article

May 1991

It is argued that recent analyses of the evolution of animal signals, which claim that signalling systems must be honest indicators of underlying quality, have neglected a vital consideration: the costs receivers pay in assessment. Where the costs of fully assessing a signaller are high, in terms of energy, time, or risk, and the value of the extra information gained is low, then it will pay receivers to settle for cheaper, but less reliable, indicators of quality instead. Thus, it is argued, honest assessment will be replaced by conventional signalling. Conventional signals are open to cheating, but cheating will be kept at low frequencies by the frequency-dependent benefits of occasional assessment (or ‘probing’), so dishonest signalling remains stable. The concept of ‘honesty’ is discussed.

MacNair MR, Parker GA. Models of parent-offspring conflict. III. Intra-brood conflict. Anim Behav 27: 1202-1209

Article

Nov 1979

A genetic model of parent-offspring conflict is developed for the situation where conflictors cause the parent to redirect resources from contemporaneous siblings to themselves, by increased solicitation. It is shown that there is no restriction on the spread of genes causing such conflict if there is no direct cost associated with it. We examine the effect of imposing on the conflictors a cost of the extra solicitation when the cost is felt (a) by the individual conflictor only, and (b) by all members of the brood equally. It is shown that the Evolutionarily Stable Strategies for the two situations allow a greater degree of solicitation when its cost is borne by the whole brood. Multipaternity of broods also increases the degree of conflict.

The function of feeding chases in the Chinstrap Penguin Pygoscelis antarctica

Article

Oct 1992

Crèching chinstrap penguin chicks chase their parents on the run before being fed. This characteristic behaviour of Pygoscelid penguins has been interpreted in several ways. In an observational study of several colonies in a rookery on Deception Island, South Shetlands, the frequency and duration of feeding chases in families with one and two chicks were compared. Significantly more feedings occurred outside the crèche in two-chick than in one-chick families. Chases were significantly more frequent and prolonged in families with two than in those with single chicks. This difference was independent of the number of chicks present in the interactions (one or two siblings in two-chick families). Chases during feedings by single chicks were significantly less frequent and prolonged than those by one chick when its sibling was absent. Siblings chasing more intensively obtained more feedings. There was no increase in chasing effort with chick age. These results suggest that feeding chases allow parents to regulate food distribution between siblings according to their needs or hunger but they could also allow brood reduction in times of food crises.

Models of parent-offspring conflict. V. Effects of the behaviour of the two parents

Article

May 1985

Geoff A. Parker

In the absence of any parent-offspring conflict, the total parental investment per offspring should be less when two parents collaborate in caring for the offspring than when only one parent invests. This does not necessarily mean that offspring fare less well when both parents invest. The ‘ideal’ amount of parental investment for an offspring to take is always greater than is ‘ideal’ for the parent to allocate (Trivers 1974). The offspring's optimum is higher if the offspring's action affects the reproductive success of only one parent and lower if both parents are affected (e.g. two-parent investment, or lifelong monogamy). The difference between the parental optimum and the offspring optimum depends on the mating system and on the form of conflict (between successive broods, or within broods), and prescribes a ‘conflict range’. The extent of conflict cannot be deduced solely from a knowledge of the average relatedness between siblings. The conflict is likely to be resolved by an ESS in which intermediate (compromise) levels of investment are paid out to offspring, which nevertheless continue to make costly demands for yet more investment. The degree of conflict can be measured by the extent to which offspring subject their parents to aggressive demands for extra investment, and is likely to be greater when two parents collaborate equally over investment than when only one parent invests. When only one parent invests, conflict is higher if sibling-competition is between siblings in the same broods (intra-brood) than when it is between progeny in successive broods (inter-brood). However, the reverse will tend to be the case when both parents invest equally.

Food Shortage Influences Sibling Aggression In The Blue-Footed Booby

Article

May 1989

In the blue-footed booby, Sula nebouxii, the first-hatched chick sometimes eliminates its broodmate in the first few weeks, when food is short. To test the hypothesis (based on descriptive data) that sibling aggression increases with food deprivation and intensifies when the senior chick's weight is 20–25% below potential, both chick's necks were taped to inhibit ingestion and behaviour was compared with controls. Under deprivation, pecking increased, rising steeply when seniors were at roughly the proposed weight threshold; begging increased, with seniors possibly suppressing begging of juniors; and in young broods (less than 6 weeks old) the senior chick's feeding advantage increased from 37 to 57% more attempted parental feeds than its sibling during deprivation. Pecking rates were more than three times higher in young broods than in old broods, where differential feeding was absent, and the effect of food deprivation on pecking increased with age in the first 6 weeks and subsequently declined with age. These age-related changes may be partly due to developmental improvement in walking ability, enabling older juniors to evade aggression. When deprivation ended, pecking, begging and feeding tended to return to baseline values, implying a reversible mechanism. The aggressive tendency of the senior chick appears to be influenced by the amount of food delivered to the brood, an effect possibly mediated by the chick's nutritional condition or hunger.

Models of parent-offspring conflict. I. Monogamy

Article

Mar 1978

Theoretical models for Trivers (1974) concept of parent-offspring conflict are examined for species in which the effects of the conflict are felt by full sibs. A rare conflictor gene will spread if (f(m) greater than 1/2(m + 1), where f(m) is the fitness gained by a conflictor relative to a non-conflictor offspring (f(m) greater than 1), and m is the amount of parental investment taken by a conflictor relative to m = 1 for a non-conflictor. The range of m alleles which can spread against the parent optimum decreases as the cost to the parent increases until a point is reached where there is no conflict of evolutionary interests. There would be no polymorphism for conflictor: non-conflictor alleles unless special conditions prevail. The conflictor allele which spreads most rapidly as a rare mutant against the parental optimum is not an evolutionarily stable strategy (ESS). The ESS for parent-offspring conflict in monogamous species has mo = f(mo)/2[df(mo)/dmo]. The analytical solutions are confirmed throughout by simulations.

The cost of honesty (further remarks on the handicap principle)

Article

Sep 1977

Amotz Zahavi

Biological Signals as Handicaps

Article

Jul 1990

Alan Grafen

An ESS model of Zahavi's handicap principle is constructed. This allows a formal exposition of how the handicap principle works, and shows that its essential elements are strategic. The handicap model is about signalling, and it is proved under fairly general conditions that if the handicap principle's conditions are met, then an evolutionarily stable signalling equilibrium exists in a biological signalling system, and that any signalling equilibrium satisfies the conditions of the handicap principle. Zahavi's major claims for the handicap principle are thus vindicated. The place of cheating is discussed in view of the honesty that follows from the handicap principle. Parallel signalling models in economics are discussed. Interpretations of the handicap principle are compared. The models are not fully explicit about how females use information about male quality, and, less seriously, have no genetics. A companion paper remedies both defects in a model of the handicap principle at work in sexual selection.

Distribution of food within broods of barn swallows

Jan 1986
286

McGillivray W. B.

The corruption of honest signalling

Jan 1991
865

Dawkins

Models of parent-offspring conflict. III. Intra-brood conflict

Jan 1979
1202

MacNair

Signalling of Nutritional Need by Magpie Nestlings

Abstract

No full-text available

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