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Effects of host sociality on ectoparasite population biology

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Abstract

Theory predicts a positive relationship between parasite infection intensity and host density. However, this generalization is complicated in natural systems by differences in life history among parasite taxa, e.g., transmissibility. Accordingly, predictions relating host density to parasite load should be specific to each parasite taxon. To illustrate this, we studied parasites that differed greatly in life history in the context of the Galapagos hawk's (Buteo galapagoensis) variably cooperative mating system. Two louse (Phthiraptera) species were collected: Colpocephalum turbinatum (Amblycera), with 53 host species, and Degeeriella regalis (Ischnocera), with 10 host species, although B. galapagoensis was the only known Galapagos host. Sixty territorial adult male hawks from 26 groups of 1-6 males were quantitatively sampled for lice. Average abundance and intensity of C. turbinatum but not D. regalis were significantly larger in large groups of hawks than small groups. Males from the same polyandrous group harbored significantly correlated abundances of C. turbinatum but not D. regalis. Prevalence, average abundance, and intensity of C. turbinatum were significantly higher than D. regalis. These are the first results to demonstrate significant differences in a suite of population responses between these louse suborders in the context of host sociality.

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... Group living may also result in increased physiological social stress due to increased competition for resources, which synergizes with host susceptibility to parasite infestation (Beldomenico and Begon, 2010;Kappeler et al., 2015). However, most studies assessing the relationship between parasitism and colonial breeding targeted monospecific colonies or the interaction between a single host and a single parasite species, overlooking the likely interactions among different hosts, or different parasites within the same hostthe parasite infracommunity (Bush et al., 1997;Holt et al., 2003;Poulin, 2007; but see Whiteman and Parker, 2004;. In fact, bird colonies are often composed of different species, resulting in mixedspecies colonies, that reshape the structure and functioning of communities through the increased interaction between the grouping species (Gaglio et al., 2018;Catry and Catry, 2019). ...
... Feather chewing lice are permanent ectoparasites with a host range usually confined to species within the same family or genus (Clayton et al., 2008). They live on the feathers and seldom leave their host except to transfer among individuals through direct contact (e.g. between parents and their offspring), and thus are likely influenced by host sociality (Clayton and Tompkins, 1995;Rózsa et al., 1996;Whiteman and Parker, 2004;Ortego et al., 2007). ...
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Coloniality in birds is often associated with an increase in parasite burden, but whether the co-occurrence of several host species influences the prevalence and abundance of ectoparasites and their relationship with colony size or density remains poorly known. Here, we studied mixed-species breeding colonies formed after the provision of artificial breeding structures for restoring the lesser kestrel (Falco naumanni) population in Portugal, to investigate the influence of colony traits on ectoparasite infestation. We sampled four groups of ectoparasites (carnid flies, haematophagous mites, louse flies and chewing lice) in four hosts: lesser kestrels, European rollers (Coracias garrulus), feral pigeons (Columba livia) and spotless starlings (Sturnus unicolor). Each host species had a distinct infracommunity of ectoparasites, regardless of colony traits such as size, density or host richness. The abundance of the most common ectoparasite, Carnus hemapterus, was influenced by colony composition – number of nests of each host species – rather than by colony size or density, with its abundance being diluted with increasing numbers of less suitable hosts such as starlings. The increased contact between multiple species of hosts in breeding colonies may complexify host–parasite interactions and challenge our current knowledge on the ecological relationships between host sociality and parasitism.
... Reducing parasite aggregation lowers within-host competition and variance in reproductive success, increasing effective population size for parasites (Whitlock and Barton, 1997;Poulin, 2007). Empirical data support reduced aggregation for ectoparasites with increased host sociality: comparative studies show reduced aggregation of lice in colonial bird species relative to territorial species (Rózsa et al., 1996;Rékási et al., 1997) and in large vs small social groups of Galapagos hawks for amblyceran lice (Buteo galapagoensis; Whiteman and Parker, 2004). Taking these processes of parasite connectivity and aggregation together, we generally expect increases in the size and connectivity of host social groups to decrease the effects of genetic drift and promote responses to selection in parasite populations (reviewed in Nadler, 1995;Barrett et al., 2008). ...
... bechsteinii) and bird (B. galapagoensis) hosts (Whiteman and Parker, 2004;Reckardt and Kerth, 2009;van Schaik et al., 2015) that produced notable changes in the population structure of wing mites and amblyceran lice, respectively. This contrast between parasite taxa highlights the fact that host social behaviour is but one of many factors that can shape parasite population genetics, and it would be valuable to weigh its relative importance across a broader diversity of host-parasite systems. ...
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An animal's social behaviour both influences and changes in response to its parasites. Here we consider these bidirectional links between host social behaviours and parasite infection, both those that occur from ecological vs evolutionary processes. First, we review how social behaviours of individuals and groups influence ecological patterns of parasite transmission. We then discuss how parasite infection, in turn, can alter host social interactions by changing the behaviour of both infected and uninfected individuals. Together, these ecological feedbacks between social behaviour and parasite infection can result in important epidemiological consequences. Next, we consider the ways in which host social behaviours evolve in response to parasites, highlighting constraints that arise from the need for hosts to maintain benefits of sociality while minimizing fitness costs of parasites. Finally, we consider how host social behaviours shape the population genetic structure of parasites and the evolution of key parasite traits, such as virulence. Overall, these bidirectional relationships between host social behaviours and parasites are an important yet often underappreciated component of population-level disease dynamics and host–parasite coevolution.
... Studies of ectoparasites in wild raptors are scarce, mainly focusing in looking for the presence of parasites in rehabilitation centers (Pérez et al., 1996;Morishita et al., 2001;Miller et al., 2004, González-Acuña et al., 2006Oliveira et al., 2011) and scientific collections (Pfaffenberger & Rosero, 1984;Hunter et al., 1994;González-Acuña et al., 2006;Bush et al., 2012). Only few studies have focused on ectoparasites in raptors at natural environments (Hunter et al., 1994;Morishita et al., 1998;Rohner et al., 2000;Whiteman & Parker, 2004a, 2004bScott et al., 2017). In nocturnal raptors few studies have been made on ectoparasites prevalence and diversity (Rohner et al., 2000;Morishita et al., 2001). ...
... Colpocephalum pectinatum is a blood-feeding louse species that can be vector of endoparasites (Whiteman & Parker, 2004b). It is then very likely that this louse may decrease the body condition of Great horned owl fledglings that have moderate to high infestation levels but also can transmit endoparasites and pathogens which in turn may affect their survival. ...
Article
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Ectoparasites are important in avian host population because they can affect health condition, regulate population dynamics and alter interspecific competition. Studies of ectoparasites in wild raptors are scarce and even few have been made in owls. This is the first study of the prevalence and intensity of ectoparasites in Great Horned Owl (Bubo virginianus) fledglings. We studied ectoparasites on fledglings from nests in a fragmented arid landscape at Baja California peninsula, during the breeding seasons of 2015 and 2017. The fledglings of 40 days of age were handled and taken from their nests for the collection of ectoparasites. A total of 81 epizoic species were collected from 36 nestlings from 15 nests, distributed in five orders: Diptera (Icosta americana); Hemiptera (Cimicidae gen. sp.); Phthiraptera (Neohaematopinus sciurinus, Colpocephalum pectinatum); Siphonaptera (Orchopea sp.) and Mesostigmata (Ornihtonysus sylviarum). Likewise, one species of chewing lice (n=5) (Geomydoecus telli) and one species of feather mite (n=7) were also recorded associated with the Great Horned Owl. Five species were hematophagous parasites. Louse fly I. americana and chewing louse C. pectinatum showed the highest levels of prevalence (26.5% and 20.6% respectively), while the hematophagous feather mite Ornihtonysus silviarum presented the higher mean intensity in only one nest (15.5). The flea Orchopea sp. and the chewing louse G. telli and sucking louse N. sciurinus exhibited the lowest values of prevalence and mean intensity; these species have been recorded in association mainly with rodents, so probably they could have been transmitted to the owls when they were captured as preys and taken into their nest. Additionally a bug (Cimicidae gen. sp.) was found in one host. Colpocephalum pectinatum is the first recorded from Great Horned owl, such as new host. The abundance of ectoparasites in one owl nest was independent of their abundance in neighbor nests (Moran´s I = 0.010; z = 0.16, P > 0.05). We discuss the implications of ectoparasitism for a Great Horned owl population in fragmented habitat of the Baja California arid desert.
... We surveyed populations of lice on adult accentors and their offspring over the course of the host´s breeding season, molting, autumn and spring (Tompkins et al. 1996, Whiteman and Parker 2004. ...
... However, little attention has been given to cooperative breeders, despite abundant data on other aspects of their biology (Heer 1994,1996, Nakamura 1995. Well documented intraspecific variation in sociality, a characteristic of some cooperative breeders, is a key advantage when relating host density to parasite abundance (Rózsa et al., 1996, Whiteman andParker 2004). From spring to autumn, the horizontal louse transmission in accentors is likely to be very low because birds maintain individual distances, also during nighting and sleeping. ...
Article
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Of the 105 inspected accentors, 52 birds yielded lice. Species Philopterus emiliae highly prevailed to Ricinus subpallidus. Only four birds were infested by both species. There was an apparent decrease in the number of lice Ph. emiliae in August and late autumn (October - November) but 85 per cent of the accentors caught in Septem- ber yielded Philopterus lice. In total, we collected 221 specimen of lice, 89 % (196) of all individuals were Ph. emiliae and only 11 % were R. subpallidus. The ratio males: females of Ph. emiliae was biased towards females from summer to winter. The average number of louse individuals was the lowest in summer, 1.8 on individual alpine accentors. Among adult birds, the female accentors were more often infested by females than males of Ph. emiliae. The female-biased sex ratios of lice and female louse loads of the females of accentors clearly signalize that there is the vertical transmission in lice in summer and autumn. The same sex ratio of lice, approximately 2:1 towards the lice females, was also found in wintering males of accentors. We hypothesize that these findings may result from the increased frequency of horizontal transmission via increased body-to body contacts among nighting accentors in winter.
... Our results support the hypothesis that water acts as a major dispersal barrier for Galápagos hawks, severely restricting gene flow among islands [12,25]. Host dispersal is limited by geographical distance among islands [25] and lice rarely move independently of their hosts [26]. Thus, we expected to find that D. regalis would show similar patterns of population divergence between islands as observed in hawks (co-divergence). ...
... Similar to the isolation and diversification of populations following establishment on an island, louse infrapopulations may undergo additional isolation events when establishing on new host individuals. Epidemiological evidence indicates that D. regalis is transmitted primarily from parent to offspring host [26]. The number of lice transmitted among hosts is expected to be small. ...
Article
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Understanding the mechanisms driving the extraordinary diversification of parasites is a major challenge in evolutionary biology. Co-speciation, one proposed mechanism that could contribute to this diversity is hypothesized to result from allopatric co-divergence of host-parasite populations. We found that island populations of the Galápagos hawk (Buteo galapagoensis) and a parasitic feather louse species (Degeeriella regalis) exhibit patterns of co-divergence across variable temporal and spatial scales. Hawks and lice showed nearly identical population genetic structure across the Galápagos Islands. Hawk population genetic structure is explained by isolation by distance among islands. Louse population structure is best explained by hawk population structure, rather than isolation by distance per se, suggesting that lice tightly track the recent population histories of their hosts. Among hawk individuals, louse populations were also highly structured, suggesting that hosts serve as islands for parasites from an evolutionary perspective. Altogether, we found that host and parasite populations may have responded in the same manner to geographical isolation across spatial scales. Allopatric co-divergence is likely one important mechanism driving the diversification of parasites.
... One of the likely costs accruing to flocking species is the increase in the risk of ectoparasite transmission, exacted by the close proximity of hundreds or thousands of individuals. Such individual proximity can favour parasite transmission in comparison with solitary species (Whiteman and Parker, 2004). Therefore, it is expected that more gregarious birds have higher parasite loads than solitary birds. ...
... Our results notwithstanding, we should caution against the easy generalization that a relationship between parasite load and sociality does not exist. Whiteman and Parker (2004) suggest that the relationship between host density and parasite abundance should be specific to each parasite taxon due to differences in the parasite biological traits such as transmissibility for instance. In this context, predictions on the relationships between parasite load abundance and host sociality can be fulfilled in more mobile parasites such as fleas, ticks or flies than less mobile parasites such as the chewing lice (Rózsa, 1997). ...
Article
Flocking behaviour does not favour high chewing lice load in shorebirds. As shorebirds show a high variability in the flocking behaviour among species from solitary ones to species forming flocks of hundreds of individuals, they offer a good opportunity to test if the proximity of individuals in highly gregarious species increases the risk of horizontal ectoparasite transmission in comparison with solitary species. We investigate whether there exists a higher ectoparasite load in gregarious shorebirds compared to solitary ones at Salinas del Cabo de Gata, Almeria, Spain. Seven species of shorebirds (Scolopacidae and Charadriidae) were captured with mist-nets during the night. Ectoparasites were estimated by means of visual examination of seven body regions and differentiated in five levels of infestation. Flock size was divided into three categories: solitary species, species forming flocks up to 99 individuals and species forming flocks of more than one hundred. Based on the application of a phylogenetic comparative method, our results show that the abundance of chewing lice is not related with flocking behaviour.
... Although it might be expected that parasites could be more abundant where woodpigeons exhibit high densities (Hoi et al., 1998), especially those that benefit from the concentration of host activities in time and space, such as chewing lice (Gil and Brumm, 2014), urbanisation appears to have a negative effect on woodpigeon ectoparasite infestation. This has greater relevance in highly gregarious species such as woodpigeons (Whiteman and Parker, 2004), which in many cases feed and roost in large numbers (Murton, 1965). In our case, despite the fact that the urban population was at least three to four times more dense, urban woodpigeons presented clearly lower parasitic infestations than the rural woodpigeons. ...
Article
The type of habitat occupied by avian populations has a marked effect on the parasitises they host. The growth of cities and urban areas in recent decades has favoured some species of birds adapted to these types of habitats - urban exploiters - although the effects of urbanisation on the parasitism of wildlife are not always well known. This study compares the ectoparasites characteristic of two differentiated populations of woodpigeons, one located in a predominantly urban environment and the other in a rural one. Most of the species found were chewing lice, with Columbicola claviformis and Campanulotes bidentatus being dominant. Despite the higher density of the urban population, woodpigeon individuals were characterised by a lower abundance of chewing lice, as well as the presence of ectoparasites typical of feral pigeons such as Hohorstiella lata and the hippoboscids fly, Pseudolynchia canariensis. Similarly, birds with lower weights showed a higher parasitic load, which became more noticeable in urban woodpigeons. The lower ectoparasite load of urban hosts represents a health advantage compared with rural populations, which could be one of the causes of greater growth and reproductive success in urban populations of woodpigeons.
... To standardize sampling effort and minimize effects of handling the animal, each bat was examined for 2 min. This sampling protocol has been effective for predicting total ectoparasite abundance in several other taxa (Whiteman and Parker, 2004). The collected ectoparasite samples were preserved in individually labeled vials with 70% ethanol until further processing. ...
Article
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Condition-dependent acoustic signals that potentially reveal information about the signaler’s physical or physiological condition are common and important in the animal kingdom. Given the negative effects of parasites on the health and fitness of their hosts, it is reasonable to expect animal acoustic signals to reflect detailed information concerning parasite infection. However, despite previous studies having verified the potential of sexually selected vocalizations to provide information on parasitism based on the correlations between call acoustic properties and parasitism in some animal taxa, less is known about whether acoustic signals used in a non-sexual context also reflect parasite infection especially for highly vocal bats. We thus investigated the relationships between the acoustic properties of distress calls and echolocation pulses and the infestation intensity of gamasid mites and bat flies in Chinese horseshoe bats (Rhinolophus sinicus) to determine whether acoustic signals potentially contain information about parasite infection. We found that bats infected with more gamasid mites uttered significantly shorter echolocation pulses, suggesting that echolocation pulses may contain information on the intensity of mite infection. Additionally, bats infected with more gamasid mites emitted distress calls with narrower bandwidth, while bats with more bat flies emitted calls with longer pause duration. These results suggest that distress calls may not only reflect a signaler’s parasite infection intensity but also may provide information concerning infection with specific parasites. In short, our findings suggest that acoustic signals of bats potentially reflect detailed information about parasite infection.
... A growing number of studies have focused on the phylogeography and population genetic relationships of rodent hosts and their associated ectoparasites showing that factors such as host switching [8][9][10], social structure of the hosts [11][12][13], and the closeness of the relationship between the host and its parasite (e.g. host specificity, [14][15][16]) determine the structure of parasitic populations. ...
Article
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Background Laelaps agilis C.L. Koch, 1836 is one the most abundant and widespread parasitic mite species in the Western Palearctic. It is a permanent ectoparasite associated with the Apodemus genus, which transmits Hepatozoon species via the host’s blood. Phylogenetic relationships, genealogy and host specificity of the mite are uncertain in the Western Palearctic. Here, we investigated the population genetic structure of 132 individual mites across Europe from their Apodemus and Clethrionomys hosts. Phylogenetic relationships and genetic variation of the populations were analyzed using cytochrome c oxidase subunit I (COI) gene sequences. Results We recovered three main mtDNA lineages within L. agilis in the Western Palearctic, which differentiated between 1.02 and 1.79 million years ago during the Pleistocene period: (i) Lineage A, including structured populations from Western Europe and the Czech Republic, (ii) Lineage B, which included only a few individuals from Greece and the Czech Republic; and (iii) Lineage C, which comprised admixed populations from Western and Eastern Europe. Contrary to their population genetic differentiation, the lineages did not show signs of specificity to different hosts. Finally, we confirmed that the sympatric congener L. clethrionomydis is represented by a separated monophyletic lineage. Conclusion Differences in the depth of population structure between L. agilis Lineages A and C, corroborated by the neutrality tests and demographic history analyses, suggested a stable population size in the structured Lineage A and a rapid range expansion for the geographically admixed Lineage C. We hypothesized that the two lineages were associated with hosts experiencing different glaciation histories. The lack of host specificity in L. agilis lineages was in contrast to the co-occurring highly host-specific lineages of Polyplax serrata lice, sharing Apodemus hosts. The incongruence was attributed to the differences in mobility between the parasites, allowing mites to switch hosts more often.
... In terms of pathogen transmission, for example, group size was long ago hypothesized to increase risk of parasite or infectious disease transmission based on the theory of island biogeography (Freeland 1979). However, while many studies provide evidence that infectious disease risk does increase in larger groups (Ezenwa 2004, Whiteman and Parker 2004, Caillaud et al. 2013, others show the opposite relationship, with smaller groups having higher levels of parasite infection (Arnold and Anja 1993, Semple et al. 2002, Bordes et al. 2007). The potential for social interactions to somehow reduce the risk of acquiring parasites led to the discovery that some properties of the social network operate as a buffer to reduce disease spread (Naug 2008, Nunn et al. 2015a, Stroeymeyt et al. 2018. ...
Article
Social structure can regulate information and pathogen transmission via social contact or proximity, which ultimately affects individual fitness. In theory, the social relationships that mediate information transmission also favor the spread of socially transmitted pathogens, creating a tradeoff between them. However, the mechanisms underlying the development and maintenance of individual relationships under such pressures remain underexplored. Here, we outline the evolutionary mechanisms of social transmission while presenting evidence that network plasticity results from individuals navigating between the costs and benefits of social relationships. We provide perspectives for the development of the field, considering this underexplored social tradeoff and the evolutionary processes underlying it. We believe that the study of the social transmission tradeoff has the potential to become a major new research direction in behavioural and evolutionary ecology.
... Different forms of sociality are thought to provide a variety of fitness benefits, including shared resources, reduced predation, improved communication or better access to mates (Eisenberg, Muckenhirn, & Rudran, 1972;Alexander, 1974;van Schaik, 1983;Emlen, 1984;Krause & Ruxton, 2002, Silk, 2007. Sociality may also come with costs associated with group living, including increased disease transmission (Ewald, 1994;Langwig, Frick, Bried, Hicks, Kunz, & Marm, 2012;Kappeler, Cremer, & Nunn, 2015), parasite load (Côt e & Poulinb, 1995;Whiteman & Parker, 2004), physiological stress (Creel, Dantzer, Goymann, & Rubenstein, 2013) and reproductive interference by other group members (Clutton-Brock et al., 1998;Lukas & Huchard, 2014), as well as the time and energy costs devoted to developing and maintaining social connections that could otherwise be devoted to activities directly related to individual survival or reproduction such as foraging or parental care. Given that these fitness benefits and costs of sociality may vary in direction or magnitude due to ecological circumstances such as food abundance, weather patterns or temporal variability in these factors (Emlen, 1994;Hatchwell & Komdeur, 2000;Rubenstein & Lovette, 2007;Schradin, K€ onig, & Pillay, 2010;Schradin & Pillay, 2005;Shen, Emlen, Koenig, & Rubenstein, 2017;Shuster & Wade, 2003), it is no surprise that there is considerable variation in the presence or expression of different types of social behaviours among species. ...
Article
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Comparative studies aid in our understanding of specific conditions favouring the initial evolution of different types of social behaviours, yet there is much unexplained intraspecific variation in the expression of social behaviour that comparative studies have not yet addressed. The proximate causes of this individual variation in social behaviour within a species have been examined in some species but its fitness consequences have been less frequently investigated. In this study, we quantified the fitness consequences of variation in the sociality of prairie voles, Microtus ochrogaster. We characterized sociality of voles in seminatural enclosures using an automated behavioural tracking system paired with social network analyses to quantify the degree of spatial and temporal co-occurrence of different voles. We then assessed the relationship between sociality and both mating success (number of different conspecifics with which an individual produced offspring) and reproductive success (total number of offspring surviving to first capture). We measured the number of social connections each individual had with all voles and with only opposite-sex voles (unweighted degree) through social network analyses. Both female and male voles varied in the number of social connections they had with all conspecifics and with opposite-sex conspecifics. In both analyses, females and males with an intermediate number of social connections had higher mating success overall and, for the analysis with all connections, produced more offspring. Males with many or few social connections also had the lowest average body mass. Overall, our results suggest some limit on the fitness benefits of sociality. Although there was substantial individual variation in our measure of vole social behaviour, intermediate levels of social connections may be most favourable.
... The macroparasites in the studies included herein were all ectoparasites, and their biology may explain our result. Ectoparasite transmission is often dependent on host-to-host contact [46,48], and thus host density is probably a critical factor in parasite success [46]. Host density may play a more important role than host genetic diversity here such that similarly aggregated populations varying in diversity might be equally susceptible to infection. ...
Article
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There is evidence that human activities are reducing the population genetic diversity of species worldwide. Given the prediction that parasites better exploit genetically homogeneous host populations, many species could be vulnerable to disease outbreaks. While agricultural studies have shown the devastating effects of infectious disease in crop monocultures, the widespread nature of this diversity-disease relationship remains unclear in natural systems. Here, we provide broad support that high population genetic diversity can protect against infectious disease by conducting a meta-analysis of 23 studies, with a total of 67 effect sizes. We found that parasite functional group (micro- or macroparasite) affects the presence of the effect and study setting (field or laboratory-based environment) influences the magnitude. Our study also suggests that host genetic diversity is overall a robust defence against infection regardless of host reproduction, parasite host range, parasite diversity, virulence and the method by which parasite success was recorded. Combined, these results highlight the importance of monitoring declines of host population genetic diversity as shifts in parasite distributions could have devastating effects on at-risk populations in nature.
... The lice of birds feed on nibbling or chewing dry skin and feathers, sweat and mucus secretion, and some lice feed on eggs and nymphs of the same type (Ford et al. 2004) and on the dry blood collected on the skin in the place of irritation caused by lice (Whiteman and Parker 2004). ...
Article
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This study was conducted to detect the chewing lice infested migratory aquatic birds in Al-Dalmaj marsh during the period from October 2017 to March 2018, for this aim 154 birds specimens belonging to 11 bird species were examined for the chewing lice infestation. Results of the current study showed recorded nine species of ectoparasites were: Menacanthus stramineus (37.01%), Menacanthus corntus (18.18%) Menacanthus eurysternus (11.04%), Menopon gallinae (18.18%), Trinoton querquedulae (5.84%) Columbicola columbae (8.44%) Aaticola crasssicorins (3.90%), Fulicoffula gallinule (3.25%) and Saemundssonia lari (2.69%), two species of them recorded for the first time in Iraq were: M. eurysternus and T. querquedulae. No significant differences between males and females birds in infested with ectoparasites, while the infestation percentage of ectoparasites significantly decreased with weight increase at level (P ≤ 0.05). The double infestation was the highest with a significant difference followed by single infestation then the triple infestation. Al-Aredhi HS, Al-Mayali HM (2019) Chewing lice parasitic on migratory aquatic birds in Al-Delmaj marsh/ Iraq. Eurasia J Biosci 13: 555-559.
... Despite the widespread nature of this pattern, there remain important gaps in our understanding of why parasite populations thrive in certain hosts and locations, but not others (Atkinson et al., 2009). In particular, it is unclear whether these aggregated distribution patterns arise solely from differences in exposure to and transmission of parasites, or if more localized effects of variation in host quality and the environment in which the parasites live is also important (Whiteman and Parker, 2004;Balakrishnan and Sorenson, 2007;Gómez-Díaz et al., 2008;Thamm et al., 2009;Dallas and Presley, 2014). The ecology and population dynamics of parasites that commonly infect humans and domesticated animals has been fairly well described; however, there is still much to learn about the ecology of parasites in wild host populations and the mechanisms that shape the distributions of these parasites across the landscape. ...
Article
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Parasite populations are never evenly distributed among the hosts they infect. Avian nest ectoparasites, such as mites, are no exception, as their distribution across the landscape is highly aggregated. It remains unclear if this pattern is driven by differences in transmission events alone, or if the environment that parasites inhabit after transmission also plays a role. Here, we experimentally examined the influence of the post-transmission microclimate, nest characteristics, and host condition on ectoparasite population growth in a bird-ectoparasite system. We infested barn swallow (Hirundo rustica erythrogaster) nests with a standardized number of Northern Fowl Mites (Ornithonyssus sylvarium) and analyzed both biotic (nestling mass, wing length, number of other arthropods present in the nest, and brood size) and abiotic (temperature, humidity, nest lining, nest dimensions, and substrate upon which the nest was built) predictors of mite population growth. Our results suggest that mite populations were most successful, in terms of growth, in nests with higher temperatures, lower humidity, few other arthropods, and hosts in good condition. We also found that nests built on wooden substrates support larger populations of mites than those constructed on metal or concrete. These findings lend insight into the factors that drive large-scale patterns of ectoparasite distributions.
... This would ensure females of the chewing louse Mulcticola macrocephalus (Kellogg, 1896) were transferred to chicks during the incubation period. In addition, ectoparasite prevalence and intensities can also differ between species and are often influenced by host characteristics, such as body size [22], bill shape and size -used for preening - [22], age related behaviour [23], sociality [24], chick development (i.e., feather growth) and nesting behaviour [25]. For example, in contrast to our findings, ectoparasite intensity on young chicks of the European bee-eater Merops Apiaster (Linnaeus, 1758) was found to be lower as compared with adults [11]. ...
... Given that this parakeet is a gregarious species living in dense colonies, it was unexpected to find so few parasites in the parakeets collected, after thorough internal and external examination (CÔTÉ & POULIN, 1995;EZENWA, 2004;WHITEMAN & PARKER, 2004;RIFKIN et al., 2012). For instance, no Argas monachus was found. ...
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Central Chile has been identified as a unique ecosystem with high conservation priority because of its high levels of endemism and intensive anthropic pressure. Over a period of almost four decades, the monk parakeet has been successful in establishing and dispersing in urban Santiago, although little is known about its potential impact. Furthermore, nothing is known about its epidemiological risks towards animals or even humans. For this reason, we conducted the first parasitic survey of monk parakeets in Chile through capture, necropsy and thorough external and internal inspection of 92 adult individuals. Among these, 45.7% presented lice that were identified as Paragoniocotes fulvofasciatum, 1.1% had mesostigmatid acari and 8.9% had free-ranging acari. Among 89 parakeets, 19.1% had structures identified as Cryptosporidium sp. This study provides the first description of Cryptosporidium sp. in monk parakeets. Along with the presence of a mesostigmatid acarus in one parakeet, this serves as a public health warning, given that both of these parasites have zoonotic potential.
... Las densidades de parásitos en un hospedero pueden variar por el acicalamiento o roce con el ambiente, el contacto con otros individuos hospedadores (sociabilidad; Whiteman & Parker 2004) o la frecuencia con que los hospedadores frecuentan sitios donde se encuentran los estados de vida libre de los parásitos (Zhang 1998;Clayton et al. 1999;Walter & Proctor 2013). ...
Thesis
Se evaluó la variabilidad morfométrica del ácaro ectoparásito Eutrombicula araucanensis entre especies de lagartijas hospederas en diferentes localidades de Chile, con el objetivo de determinar si la identidad de la especie hospedera y la intensidad de infestación producen cambios en la morfometría del ácaro. Para evaluar la morfometría de los ácaros se trabajó con 794 E. araucanensis extraídos desde 172 lagartijas pertenecientes a cinco especies: Liolaemus pictus, L. tenuis, L. lemniscatus, L. septentrionalis y Pristidactylus torquatus capturadas en 11 localidades de Chile. Se seleccionó desde cada hospedador tres ácaros en promedio (n=111), a los que se les realizó morfometría tradicional considerando las medidas de setas y longitudes del escudo dorsal. Las variables obtenidas fueron resumidas mediante un análisis de componentes principales y posteriormente se realizó un análisis discriminante para evaluar diferencias atribuidas a la identidad del hospedador. La identidad de cada especie de lagartija hospedera se caracterizó mediante el largo, peso, comportamiento, hábito y hábitat, para posteriormente evaluar el efecto de la identidad del hospedero en la morfometría de E. araucanensis mediante regresión logística multinomial. Se evaluó las diferencias atribuidas a la localidad mediante un análisis discriminante. Para evaluar el efecto de la intensidad de infestación con el tamaño de los ácaros se realizó una regresión lineal en cada especie de lagartija por separado. Eutrombicula araucanensis mostró variación morfométrica, sin embargo, esta variación no estuvo asociada a la identidad de la especie hospedadora, sino más bien a la localidad de muestreo. Probablemente existe un límite geográfico de variación morfométrica en los 38°S que esté aislando a E. araucanensis. No hubo diferencias morfométricas de E. araucanensis con respecto al nivel de infestación en ninguna especie de lagartija, probablemente la intensidad de infestación deba ser mayor para causar diferencias morfométricas en los parásitos. Se concluye que E. araucanensis es un ácaro que presenta amplia variabilidad morfométrica dada por la localidad más que por efecto de la especie hospedera o por el nivel de infestación.
... Moving beyond single-species studies, research comparing networks across species offers valuable insights to fundamental questions at the nexus of animal behavior and disease ecology. For example, infection risk is often predicted to increase with group size [5]; however, studies examining this relationship offer mixed results (e.g., [42,43]). Griffin et al. studied empirical social networks for 19 primate species and found that larger groups tended to exhibit higher modularity (i.e., subgrouping) and lower parasite species richness, indicating that modularity may reduce infection risks in large groups [25]. ...
Article
Social interactions are important in everyday life for primates and many other group-living animals; however, these essential exchanges also provide opportunities for parasites to spread through social groups. Network analysis is a unique toolkit for studying pathogen transmission in a social context, and recent primate–parasite network studies shed light on linkages between behavior and infectious disease dynamics, providing insights for conservation and public health. We review existing literature on primate–parasite networks, examining determinants of infection risk, issues of network scale and temporal dynamics, and applications for disease control. We also discuss analytical and conceptual gaps that should be addressed to improve our understanding of how individual and group-level factors affect infection risk, while highlighting interesting areas for future research.
... In the absence of data on transmission rates for the vast majority of bat pathogens, we assumed transmission rate values for our models. Transmission rate is a function of the host-parasite system (Fenton et al. 2002) and variation in transmission can be influenced by intrinsic characteristics of the host, like mating strategy or dispersal ability (Whiteman and Parker 2004) both of which can be linked to sociality. To our knowledge, no comprehensive review exists linking host social behavior of bats (i.e., group size, mating system or any index of sociality) to any measurement of parasitism, including diversity, abundance, or rate of transmission, although such studies exist for rodents (e.g., Bordes et al. 2007), primates (e.g., Nunn et al. 2003), and ungulates (e.g., Ezenwa 2004). ...
Article
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Host behavior can affect host-pathogen dynamics, and sociality is predicted to increase risk of pathogen exposure. Many species minimize costs of parasitism by only aggregating seasonally, such as during reproductive periods, but colonial species may still be limited in their potential to evade pathogens. Bats are among the most gregarious mammals and females of many temperate species form maternity colonies in summer where they communally raise pups in both natural and anthropogenic roost structures. Social network structure may differ between natural and anthropogenic roosts in ways that affect pathogen dynamics. We used social network analysis to quantify interactions of big brown bats (Eptesicus fuscus) in a tree-roosting colony, where the colony is divided among multiple trees each day, and a building colony, where most of the colony roosts together each day. We simulated transmission of a pathogen throughout both sets of networks. We tested three hypotheses: (1) network metrics differ between pregnancy and lactation; (2) changing network structure between reproductive stages influences predicted pathogen dynamics; and (3) network metrics and predicted pathogen dynamics differ between colonies of bats in trees versus buildings. Network structure was weaker for bats roosting in trees during pregnancy and lactation compared to bats roosting in a building, and our models showed that a hypothetical pathogen would spread more rapidly for bats in the building colony. Our results are important for understanding variation in social tendencies and pathogen transmission among colonies of bats and have implications for conservation and public health. Significance statement Host behavior, particularly social behavior, can affect dynamics of wildlife pathogens. Bats are highly social mammals and females of temperate species form colonies in spring and early summer in tree or building roosts. Thermal characteristics of trees and buildings appear to differ in ways that affect roosting behavior and social interactions. We used social network analyses to quantify interactions of big brown bats in tree and building roosts and simulated consequences for pathogen dynamics. Network structure was weaker for bats roosting in trees with more frequent roost switching and relatively diffuse contacts across the network. Our models showed that a hypothetical pathogen could spread up to four times faster in a building colony compared to a colony of bats roosting in trees. Our results are important for understanding how sociality can influence pathogen dynamics in bats and have implications for conservation and public health.
... Within animal populations, there is considerable heterogeneity in the degree to which individuals are parasitized, with a minority of hosts harboring the majority of parasites Poulin 2007). Beyond the contribution of environmental conditions (such as rainfall, for instance: Altizer et al. 2006) and parasite-specific characteristics (including transmission mode: Whiteman and Parker 2004;Bordes et al. 2007;Viljoen et al. 2011), variation in host susceptibility and exposure to parasites may owe to factors intrinsic to the host or related to its species' social organization. These influential factors may include the host's body condition (Ezenwa and Jolles 2008;Turner et al. 2012), age (Hayward et al. 2009;Gillespie et al. 2010), social status (Muehlenbein and Watts 2010;Hawley et al. 2011;Fairbanks and Hawley 2012), sex (Moore and Wilson 2002;Poulin 1996;Zuk and McKean 1996), reproductive state (Hausfater and Watson 1976;Festa-Bianchet 1989), and group size (Côté and Poulin 1995;Rifkin et al. 2012). ...
Article
Within animal societies, demographic and social factors, as well as the different reproductive efforts of group members, may influence individual patterns of reproductive success and parasitism. In mammals, such relationships have been studied primarily in male-dominant species. To better understand these linkages in other social systems, we studied a female-dominant cooperative breeder, the meerkat (Suricata suricatta). This species is characterized by intense intrasexual competition and extreme reproductive skew in both sexes. Within adults, we examined heterogeneities in infection by 6 species of endoparasites in relation to host factors (e.g., weight, age, social status, sex, and group size). We explored potential trade-offs between reproduction and parasitism in dominant and subordinate animals of both sexes. Whereas weight and age were predictive of a few parasite taxa, social status or sex predicted parasite species richness and patterns of infection for the majority of parasites examined. Moreover, a significant interaction between sex and status for 2 nematode taxa revealed that dominant females were the most at risk of infection. Lastly, a positive relationship between group size and parasitism was evident in females only. In sum, compared with subordinates, dominant meerkats may experience increased exposure to directly transmitted parasites. Coupled with hormone-mediated immunosuppression, the increased susceptibility of dominant females may reflect energy allocation for preferentially maintaining dominance and breeding status over parasite defense. In species in which female intrasexual competition is intense, this trade-off between reproduction and health may be more pronounced in females than in males.
... There are several reasons why increases in the density or contact rate of hosts may fail to increase parasite transmission. The response of parasite prevalence and abundance may differ as a function of the route of transmission (Arneberg 2001, Fenton et al. 2002, Whiteman and Parker 2004 or dilution effects . Long-term increases in parasite burden due to increased host density or contact are even more difficult to predict, as host species may display density-dependent disease resistance (Wilson et al. 2002a), acquired immunity (Craig et al. 1996), or alterations in behaviors that reduce risk and extent of infection (Loehle 1995). ...
... Some empirical evidence supports this prediction. For example, Whiteman & Parker [5] found higher louse abundance in larger aggregations of Galapagos hawks (Buteo galapagoensis), while Ezenwa [6] discovered a positive association between prevalence of intestinal parasites and group size in African artiodactyls. Across primates, malaria prevalence increases with group size in comparative tests [7,8], and a recent study found evidence for positive selection on genes related to immunity in species living in larger groups [9]. ...
Article
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Increased risk of infectious disease is assumed to be a major cost of group living, yet empirical evidence for this effect is mixed. We studied whether larger social groups are more subdivided structurally. If so, the social subdivisions that form in larger groups may act as barriers to the spread of infection, weakening the association between group size and infectious disease. To investigate this 'social bottleneck' hypothesis, we examined the association between group size and four network structure metrics in 43 vertebrate and invertebrate species. We focused on metrics involving modularity, clustering, distance and centralization. In a meta-analysis of intraspecific variation in social networks, modularity showed positive associations with network size, with a weaker but still positive effect in cross-species analyses. Network distance also showed a positive association with group size when using intraspecific variation. We then used a theoretical model to explore the effects of subgrouping relative to other effects that influence disease spread in socially structured populations. Outbreaks reached higher prevalence when groups were larger, but subgrouping reduced prevalence. Subgrouping also acted as a 'brake' on disease spread between groups. We suggest research directions to understand the conditions under which larger groups become more subdivided, and to devise new metrics that account for subgrouping when investigating the links between sociality and infectious disease risk. © 2015 The Author(s) Published by the Royal Society. All rights reserved.
... Many factors have been postulated to affect prevalence and intensity of flea parasitism among and within host species (Krasnov et al., 2002c;Whiteman and Parker, 2004;Krasnov et al., 2005;Kiffner et al., 2013). Most factors fall broadly into 2 categories: host factors and environmental factors. ...
Article
The relative importance of both environmental factors and host factors in explaining variation in prevalence and intensity of flea parasitism in small mammal communities is poorly established. We examine these relationships in an East African savanna landscape, considering multiple host levels: across individuals within a population, across populations within species, and across species within a landscape. We sampled fleas from 2672 small mammals of 27 species. This included a total of 8283 fleas, with 5 genera, and 13 species identified. Across individual hosts within a site, both rodent body mass and season affected total intensity of flea infestation, although the explanatory power of these factors was generally modest (<10%). Across host populations in a landscape we found consistently positive effects of host density and negative effects of vegetation cover on the intensity of flea infestation. Other factors explored (host diversity, annual rainfall, anthropogenic disturbance, and soil properties) tended to have lower and less consistent explanatory power. Across host species in the same landscape, we found that host body mass was strongly positively correlated with both prevalence and intensity of flea parasitism. The average robustness of a host species to disturbance was not correlated with flea parasitism. Cumulatively, these results provide insight into the complex roles of both intrinsic (host) and extrinsic (environmental) factors in explaining complex patterns of flea parasitism across a landscape.
... Similarly cooperatively breeding species, which live and interact at higher local densities, may be subject to higher rates of parasitism than pair breeding species. Indeed, there is some evidence that cooperatively breeding birds may invest more in parasite defence than pair breeding birds (Spottiswoode, 2008) and Whiteman and Parker (2004) found ectoparasite infection increased with group size in cooperatively breeding Galapagos hawks (Buteo galapogoensis). In contrast, there was no effect of group size on presence of malaria in the Seychelles warbler. ...
Article
This copy of the thesis has been supplied on condition that anyone who consults it is understood to recognise that its copyright rests with the author and that no quotation from the thesis, nor any information derived therefrom, may be published without the authors prior, written consent.
... However, flocking can also have negative effects on individuals. For example, living in large flocks increase aggression and intraspecific competition and may provide greater exposure to parasites or disease vectors (KRAUSE & RUXTON 2002, WHITEMAN & PARKER 2004, BEAUCHAMP 2007. Therefore, it is of conservation and ecological interest to understand whether individuals experience different crowdedness conditions in different-sized flocks as these experiences may be directly related to the costs and benefits of flock formation. ...
Article
Migrating in flocks has various benefits but also incurs costs, which depend on the conditions individuals experience in flocks of various sizes. Here we quantified such conditions by using recently developed methods to measure crowdedness in animal groups using data on flock sizes of the endangered Fennoscandian population of the globally threatened Lesser White-fronted Goose Anser erythropus. Data were gathered on migration in Hortobágy National Park (E Hungary) between 1994 and 2006. Data on 548 sightings of the species suggested that the dis-tribution of flock sizes was skewed and that flock sizes were significantly larger in the autumn than in the spring. Despite this difference, mean crowding values, i.e., the group size in which an average individual occurs, were remarkably similar in the spring and in the autumn. These results show that even though flock size varied seasonally, the social environment experienced by the average individuals was surprisingly stable across seasons. Such stability can be impor-tant in the consistency of the benefits and costs of migrating in flocks. Our results also draw at-tention to the importance of quantifying crowdedness in animal groups as these measures can provide information different from those provided by looking at mean group size alone.
... An alternative explanation for the outliers is host dispersal. Symbiont dispersal abilities are related to host dispersal range (Whiteman & Parker, 2004), and P. clarkii populations are subject to dispersal movements of up to 2.5 km (Siesa et al., 2011). ...
Article
Symbiosis represents a widespread and successful lifestyle, but research on symbiotic associations has been mainly focused on parasites. Three general patterns in parasite ecology have been proposed: (i) aggregation, (ii) positive and tight correlation between mean symbiont abundance and its variance and (iii) positive correlation between abundance and prevalence of symbionts. The factors affecting abundance and prevalence within symbiont species can be grouped into host features and environmental conditions. According to research in parasite ecology, environmental conditions seem to play a minor role. We investigated whether the three most recognised parasite patterns were also evident in a non‐parasitic freshwater ectosymbiont and analysed the effects of host features (sex, body size, density and ecdysis) and environmental conditions (climate and water chemistry) on abundance and prevalence of the symbiont. Our species model was an exotic ectocommensal ostracod, A nkylocythere sinuosa , inhabiting the invasive crayfish P rocambarus clarkii in Europe. We sampled 373 crayfish from 26 Spanish localities. We modelled both abundance per occupied host (i.e. intensity) and prevalence using zero‐altered models and a backward model selection of host and environmental variables, and assessed model performance through graphical analyses of Pearson residuals and the relationship between observed and fitted values of the finally selected model. We observed all three parasite patterns in A. sinuosa . Abundance of A. sinuosa was most strongly related to conductivity (negative effect), followed by host density (positive) and ecdysis (negative), with moderate relationships to variables related to water chemistry ( concentration, alkalinity/(Cl ⁻ + ) and Cl ⁻ / ratios). Prevalence was related mainly to crayfish density (positive effect) and also to climatic conditions (maximum temperature of warmest month, annual precipitation and precipitation seasonality). Our results suggest that some ‘parasite rules’ may actually be general ‘symbiont rules’. Moreover, our symbiont model was markedly affected by climatic conditions at a regional scale acting on prevalence, and water chemistry at a local level acting on symbiont abundance. This supports the hypothesis of a prominent role of environmental conditions influencing population parameters of non‐parasitic freshwater ectosymbionts. Physiological tolerances to highly unstable environmental factors, together with dependence on highly variable external food sources, probably underlie the high sensitivity to environmental conditions of this category of symbiont.
... Therefore, social insects are highly exposed to epidemics. Living enclosed in stable humid environments even up to several years, in dense groups of genetically related individuals with frequent contact and exchange of fluids, and with high energy supplies stored in the form of brood and food reserves, the colonies of social insects offer ideal conditions for the invasion by and dispersion of parasites and infectious diseases [6,34,35,[60][61][62]. ...
Article
Full-text available
The successful life of insect societies has evolved from the division of labor among more or less specialized individuals, who carry out all necessary tasks for the maintenance and growth of the colony. The extreme division of labor has produced workers specialized in the removal of dead members of the colony, an evident and highly stereotyped behavior called undertaking which consists of the ability to recognize and dispose of the dead members of the colony using specific chemical cues. Although living in enclosed nests has contributed to the ecological success of social insects due to environmental control, it also poses disadvantages. Nests of social insects, containing dense groups of genetically close individuals with frequent physical contact, present ideal conditions for the incidence and dispersion of infectious diseases. To maintain strict microbiological control inside the nest, these insects have evolved hygienic behavioral strategies to avoid and control the proliferation of pathogens. Undertaking behavior is one of the fundamental strategies to exert microbiological control inside the nest by means of suitable management and removal of dead members of the colony, to prevent the emergence of epidemics that may lead the insect society to extinction. Therefore, undertaking behavior has been fundamental to the evolution of social insects. This stereotyped behavior constitutes an excellent model for the understanding of both social evolution and the neurobiological basis of social behavior. In this paper, we review the present knowledge on undertaking behavior, and outline some perspectives of the study of such far-reaching behavior of social organization.
... The amount of time spent on visual examination and dust-ruffling has varied among studies (Lindell et al. 2002, Whiteman and Parker 2004, Balakrishnan and Sorenson 2007, Martin et al. 2007). Long observation times or repeated bouts of ruffling may stress birds (Silverin 1998). ...
Article
Two methods commonly used to quantify ectoparasites on live birds are visual examination and dust-ruffling. Visual examination provides an estimate of ectoparasite abundance based on an observer's timed inspection of various body regions on a bird. Dust-ruffling involves application of insecticidal powder to feathers that are then ruffled to dislodge ectoparasites onto a collection surface where they can then be counted. Despite the common use of these methods in the field, the proportion of actual ectoparasites they account for has only been tested with Rock Pigeons (Columba livia), a relatively large-bodied species (238-302 g) with dense plumage. We tested the accuracy of the two methods using European Starlings (Sturnus vulgaris; ~75 g). We first quantified the number of lice (Brueelia nebulosa) on starlings using visual examination, followed immediately by dust-ruffling. Birds were then euthanized and the proportion of lice accounted for by each method was compared to the total number of lice on each bird as determined with a body-washing method. Visual examination and dust-ruffling each accounted for a relatively small proportion of total lice (14% and 16%, respectively), but both were still significant predictors of abundance. The number of lice observed by visual examination accounted for 68% of the variation in total abundance. Similarly, the number of lice recovered by dust-ruffling accounted for 72% of the variation in total abundance. Our results show that both methods can be used to reliably quantify the abundance of lice on European Starlings and other similar-sized passerines.
... Also, colony size and density can influence individual parasite loads and prevalence (Marshall 1982;Walter 1996). Because host population size and density affect parasitism, roosting biology is expected to influence parasite load or prevalence Whiteman and Parker 2004). ...
Article
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We investigated the ectoparasitic mite loads (Macronyssus: Macronyssidae: Acarina) on 2 species of flat-headed bats, Tylonycteris pachypus and T. robustula (Mammalia: Chiroptera: Vespertilionidae) in 2 counties of Guangxi Province, southern China, from 2002 to 2005. In Longzhou County both species of bat occur sympatrically, but only T. pachypus occurs in Ningming County. Individuals of the smaller species (T. pachypus) harbored significantly more mites than did those of T. robustula. In both species males harbored more mites than nonreproductive females, pregnant females had more mites than lactating and nonreproductive females, and juveniles harbored more mites than adults. Mite load on both species of bats showed significant seasonal variation, declining from spring to winter. No correlation was found between mite load and size of the host colony. We discuss our findings in relation to the ecology and biology of both hosts and parasites.
Article
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The crested ibis has survived a dramatic population decline during the twentieth century, declining from a range across much of China, Japan, the Korean peninsula and nearby Russia, to a known world population of seven individuals. These formed the basis of a successful breeding program in Shaanxi, China. We examined ibises in this breeding program for ectoparasites, to establish whether any of the three chewing louse species known from this host had survived this severe host population bottleneck. We recovered representatives of three species of lice, identified as the same species as those previously known from the wild populations: Ardeicola nippon, Colpocephalum nipponi, and Ibidoecus meinertzhageni. Of these, the two first species were recovered from almost all examined hosts, whereas I. meinertzhageni was more rare. As these lice are host specific, this implies that all three louse species remarkably survived this bottleneck, and are now thriving in both the reintroduced and captive populations of crested ibis. This constitutes an unintentional success story in the conservation of parasitic species. We provide the first photos of all three species, as well as a preliminary assessment of their conservation status, and discuss the future of chewing louse conservation.
Article
In the past 25 years, studies on interactions between chewing lice and their bird hosts have increased notably. This body of work reveals that sampling of live avian hosts, collection of the lice, and the aggregated distributions of louse infestations pose challenges for assessing louse populations. The number of lice on a bird varies among host taxa, often with host size and social system. Host preening behavior limits louse abundance, depending on bill shape. The small communities of lice (typically one–four species) that live on individual birds show species-specific patterns of abundance, with consistently common and rare species, and lower year-to-year population variability than other groups of insects. Most species of lice appear to breed continuously on their hosts, with seasonal patterns of abundance sometimes related to host reproduction and molting. Competition may have led to spatial partitioning of the host by louse species, but seldom contributes to current patterns of abundance.
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Despite the key role that knowledge on breeding biology of Accipitriformes plays in their management and conservation, survey of the state-of-the-art and of information gaps spanning the entire Neotropics has not been done since 1995. We provide an updated classi cation of current knowledge about breeding biology of Neotropical Accipitridae and de ne the taxa that should be prioritized by future studies. We analyzed 440 publications produced since 1995 that reported breeding of 56 species. ere is a persistent scarcity, or complete absence, of information about the nests of eight species, and about breeding behavior of another ten. Among these species, the largest gap of breeding data refers to the former “Leucopternis” hawks. Although 66% of the 56 evaluated species had some improvement on knowledge about their breeding traits, research still focus disproportionately on a few regions and species, and the scarcity of breeding data on many South American Accipitridae persists. We noted that analysis of records from both a citizen science digital database and museum egg collections signi cantly increased breeding information on some species, relative to recent literature. We created four groups of priority species for breeding biology studies, based on knowledge gaps and threat categories at global level. Group I (great scarcity of information, plus higher categories of threat): Leptodon forbesi, Cryptoleucopteryx plumbea, and Buteogallus lacernulatus; Group II (breeding data have recently increased, but threat categories are high): Spizaetus isidori, Accipiter gundlachi, Buteogallus coronatus, Pseudastur occidentalis, and Buteo ventralis; Group III (“Near reatened” species with still scarce breeding information): Accipiter poliogaster, Accipiter collaris, Buteogallus aequinoctialis, and Pseudastur polionotus; and Group IV (other priority cases): Buteo ridgwayi, Buteo galapagoensis, four eagles (Morphnus guianensis, Harpia harpyja, Spizaetus ornatus and Buteogallus solitarius), Leptodon cayanensis, Accipiter superciliosus, Buteogallus schistaceus, and the three Leucopternis hawks (L. semiplumbeus, L. melanops and L. kuhli). We also discuss the way that novel breeding data can show in what manners di erent species and populations are responding to environmental changes.
Technical Report
Durante los días 5–9 de diciembre de 2016, el taller para desarrollar un Plan de Salud de la Vida Silvestre de Galápagos se llevó a cabo en Puerto Ayora, Galápagos. Al taller asistieron 43 participantes representantes de organizaciones estatales en Ecuador (Agencia de Regulacióny Control de la Bioseguridad y Cuarentena para Galápagos, Dirección del Parque Nacional Galápagos, Instituto Nacional de Biologíay Ministerio de Agricultura, Ganadería, Acuacultura y Pesca); universidades tanto del Ecuador (Escuela Superior Politécnica del Litoral –Facultad de Ciencias de la Vida, Universidad Central del Ecuador, y Universidad San Francisco de Quito) como de Estados Unidos (Colorado State University; North Carolina State University College of Veterinary Medicine; University of California, Davis School of Veterinary Medicine; and College of Veterinary Medicine, University of Minnesota); funcionarios/as de organizaciones de conservación no gubernamentales con base en las Galápagos (Fundación Charles Darwin, Island Conservation, Galápagos Conservancy,Sea Shepherd, y WILDAID) así como otras organizaciones internacionales (Houston Zoo,San Diego Zoo Global, San Diego Zoo, Wildlife Conservation Society, Zoological Society of London y Fundación Pro Zoológicos). La Visión del Plan de Salud para los próximos 25 años es la siguiente: “Un impacto antropogénico menor y decreciente habilita ecosistemas funcionales y resilientes que sostienen poblaciones silvestres saludables, en equilibrio con sus parásitos naturales, y cumplen con sus roles ecológicos.” Definimos parásitos en el sentido ecológico amplio, incluyendo virus, bacterias, hongos, protozoos, helmintos, artrópodos, y anélidos que tienen un ciclo de vida parasitario. Las actividades del taller siguieron los procesos de trabajo de CBSG, donde los expertos ensalud de vida silvestre conformaron seis gruposde trabajo para analizar la situación actual y recomendaron prioriades de salud de las especiesnativas de Galápagos, especies domésticas ysilvestres, y sus ecosistemas. Estos grupos fueron los siguientes: Reptiles Endémicos de Galápagos Aves Endémicas de Galápagos Mamíferos Endémicos de Galápagos Especies Introducidas e Invasoras en Galápagos Animales Domésticos Protocolos y Recopilación de Datos cuando se Manipulan Animales Silvestres
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Selected haemetophagous phthirapterans have been convicted to act as reservoir and transmitter of pathogens among their hosts. Amblyceran Phthiraptera are generally believed to exhibit varying degree of haemetophagy. The microscopic examination of 100 adults (both sexes) and 47 nymphal instars of an amblyceran louse, Colpocephalum turbinatum revealed their non haemetophagous nature as any red content compatible with host blood was not detected in their crops. The crops of the lice were found packed with only feather barbules. On seven instances the pieces of egg chorion and in 20 cases the presence of epidermal tissue were also detected in crop contents. However, the presence of any triturating agent (any structure which can help in grinding the feather contents) was not noticed. SEM studies on the ventral side of the head of the louse do not indicate the presence of any pointed gear which can be used to pierce the skin blood vessels of host. Present study suggests that few amblyceran species of Phthiraptera are not in haemetophagous in nature.
Chapter
A parasite depends, during its entire life or at least part of it, on other organisms, but parasites often “jump” from one host species to another and may be able to colonize new host species. The chances of parasite spillover, the first step in such a host switch, may be influenced by factors such as the local ecosystem, community composition, and modes of transmission, among others. In Galapagos, for example, seabirds show a spatially clustered community, with several species that are related and/or nest in close proximity, a seemingly perfect scenario for host switching. However, only one instance of a straggling ischnoceran louse and larva (indicating successful reproduction on the new host) was found on a different host species, suggesting that the specifics of ectoparasite body size and host feather interbarbular space may prevent lice from readily switching hosts. On the other hand, the haemosporidian parasite, Haemoproteus multipigmentatus, of the Columbiform-specific sub-genus Haemoproteus, was found in significant numbers of Galapagos passerines. The spillover events occur where Galapagos doves (Zenaida galapagoensis), a widespread endemic, are present or abundant enough; however, there is no evidence of parasite development in the passerine birds. Thus, the Galapagos archipelago provides an exceptional host-parasite system to investigate details of parasite spillover and its implications for host health and survivorship.
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Parasite lineages commonly diverge when host lineages diverge. However, when large clades of hosts and parasites are analyzed, some cases suggest host switching as another major diversification mechanism. The first step in host switching is the appearance of a parasite on an atypical host, or “straggling.” We analyze the conditions associated with straggling events. We use five species of colonially nesting seabirds from the Galapagos Archipelago and two genera of highly specific ectoparasitic lice to examine host switching. We use both genetic and morphological identification of lice, together with measurements of spatial distribution of hosts in mixed breeding colonies, to test: (1) effects of local host community composition on straggling parasite identity; (2) effects of relative host density within a mixed colony on straggling frequency and parasite species identity; and (3) how straggling rates are influenced by the specifics of louse attachment. Finally, we determine whether there is evidence of breeding in cases where straggling adult lice were found, which may indicate a shift from straggling to the initial stages of host switching. We analyzed more than 5,000 parasite individuals and found that only ~1% of lice could be considered stragglers, with ~5% of 436 host individuals having straggling parasites. We found that the presence of the typical host and recipient host in the same locality influenced straggling. Additionally, parasites most likely to be found on alternate hosts are those that are smaller than the typical parasite of that host, implying that the ability of lice to attach to the host might limit host switching. Given that lice generally follow Harrison's rule, with larger parasites on larger hosts, parasites infecting the larger host species are less likely to successfully colonize smaller host species. Moreover, our study supports the general perception that successful colonization of a novel host is extremely rare, as we found only one nymph of a straggling species, which may indicate successful reproduction.
Article
A look on literature revealed that the population characteristics of Phthiraptera infesting Black Kite, Milvus migrans Boddaert deserved investigation. Thirty-two kites were sampled in district Rampur (U.P.) India during January 2011–December 2012, for the presence of phthirapteran ectoparasites. Two amblyceran species, Laemobothrion maximum Scopoli and Colpocephalum turbinatum Denny and one ischnoceran louse, Degeeriella regalis Giebel were recovered. The prevalence, intensity of infestation, sample mean abundance, range of infestation, sex ratios, and adult nymph ratios of three lice were recorded. C. turbinatum ranked first in the order of prevalence and intensity of infestation, followed by D. regalis. The prevalence and intensity of L. maximum was quite low.
Article
A cross-sectional survey was conducted in order to determine the epizootiology of ectoparasitic fauna infesting domestic cattle population of district Toba Tek Singh (T.T. Singh), Punjab, Pakistan. A questionnaire-based surveillance of 3864 cattle respondents, randomly selected through two-stage cluster sampling was conducted over a period of one year from March, 2011 to February, 2012. A total of 822 (21.27%) subjects were found infested with ectoparasites including ticks (39.1%), mites (4.34%), lice (23.23%), fleas (0.89%) and flies (5.32%). Taxonomic studies revealed following species: Hyalomma anatolicum and Rhipicephalus microplus of ticks; Ctenocepahlides (Ct). felis and Ct. canis of fleas; Haematopinus eurysternus, Damalinia bovis and Linognathus vituli of lice; Psoroptes bovis and Sarcoptes scabei of mites; and Stomoxys calcitrans of flies. Friesian cattle (Bos taurus) was significantly more proned to infestation as compared to Jersey (Bos taurus), cross-bred (Bos taurus × Bos indicus) and Sahiwal (Bos indicus). Among various determinants, age and sex of host; feeding and animal keeping systems were not found statistically associated with the prevalence of ectoparasites (P>0.05). However, cemented floor was having a positive statistical association with the ectoparasites (P<0.05). The prevalence of fleas, lice and mites was found higher in winter, while prevalence of ticks and fly reached to their peaks in summer and spring seasons, respectively. The data corresponds to a significant chapter of domestic cattle population and can help to restrict the spread of invasion, which causes skin and hide quality squalor and disease spread in the area.
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We tested for associations between body condition, territory ownership, and permanent parasite load of Galápagos Hawks (Buteo galapagoensis) on Isla Marchena, Galápagos. Two louse species were collected from most of the 26 hawks sampled: the amblyceran Colpocephalum turbinatum and the ischnoceran Degeeriella regalis. Nonterritorial hawks were in significantly poorer body condition than territorial hawks. Body condition was negatively correlated with the abundance of C. turbinatum. Nonterritorial hawks had significantly higher mean abundances, mean intensities, and median intensities of both louse species than territorial hawks. The amblyceran's mean abundance and intensity were significantly higher than the ischnoceran's. Abundances of the two lice were positively related when the population size of C. turbinatum was <100 individuals, and negatively related when >100 individuals. Parasite load and body condition both predicted territory ownership well. La Condición Corporal y la Carga Parasitaria Predicen la Posesión de Territorios en Buteo galapagoensis Resumen. Probamos la relación entre la condición corporal, la posesión de territorios y la carga parasitaria permanente en el Gavilán de Galápagos (Buteo galapagoensis) en la Isla Marchena, Galápagos. En la mayoría de los 26 gavilanes muestreados se colectaron dos especies de piojo: el ambliceránido Colpocephalum turbinatum y el ischnoceránido Degeeriella regalis. Los gavilanes no territoriales se encontraron en condiciones corporales significativamente peores que los gavilanes territoriales. Encontramos una correlación negativa significativa entre la condición corporal y la abundancia de C. turbinatum. Los gavilanes no territoriales tuvieron significativamente mayor abundancia, intensidad media e intensidad mediana de las dos especies de piojo que los gavilanes territoriales. La abundancia promedio y la intensidad de los ambliceránidos fueron significativamente mayores que las de los ischnoceránidos. Las abundancias de las dos especies de piojo estuvieron positivamente correlacionadas cuando el tamaño poblacional de C. turbinatum fue <100 individuos y negativamente correlacionadas cuándo fue >100 individuos. Tanto la carga parasitaria como la condición corporal predijeron bien la posesión de territorios.
Article
Population parameters of ectoparasites on feral pigeons, Columba livia Gmelin (Aves: Columbiformes: Columbidae), were estimated from 1995–2012 in southern Manitoba, Canada. The ectoparasites are chewing lice (Phthiraptera): Philopteridae – Campanulotes compar (Burmeister), Columbicola columbae (Linnaeus), and Coloceras tovornikae Tendeiro; Menoponidae – Hohorstiella lata (Piaget). We tested the hypotheses that both abundance and population stability are species-specific traits. Over 10 years, the four species of lice had distinct population dynamics. Campanulotes compar and C. columbae were more abundant than C. tovornikae and H. lata, had higher male to female sex ratios and higher ratios of nymphs to females, different levels of aggregation, and more stable populations. Campanulotes compar was more prevalent than C. columbae and its prevalence was more stable, and the two species also showed differences in the levels and stabilities of male and nymph to female ratios. Coloceras tovornikae had a higher prevalence and male to female sex ratio than H. lata, but the two species showed similar levels of stability for these parameters. The level of stability of these populations was relatively high compared with many other organisms, and in particular higher than for plant ectoparasites (Hemiptera: Aphididae). Although the four species occupy similar habitats, often on the same bird, and three of the four feed in a similar way, the population biology of each species is distinct. The life history traits that lead to these differences have yet to be determined.
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We list all described species and subspecies of parasitic lice from the Galápagos Islands, based on literature and specimen records. A total of eight families, 47 genera, and 104 species and subspecies of parasitic lice are listed, of which 26 are new species records and eight are new genus records. Also, we report 17 new host-louse associations. The checklist includes 17 endemic species (16 from birds, one from a mammal), 79 native species and subspecies (78 from birds, one from a mammal), and eight species and subspecies (five from birds, three from mammals) introduced by human agency. Nine species assigned in error to the Galápagos Islands in the literature are discussed and deleted from the fauna. For each valid species and subspecies we give information on its taxonomic history, type material, host associations, geographic distribution, biogeographical status, systematic relationships, and relevant literature references. We also give a brief summary of louse biology, and an account of the history of louse collecting, expeditions, collections, and research relating to Galápagos Islands lice. We include a host-parasite list, and a list of hosts which breed in the Galápagos Islands but without lice recorded from them. Also, we formally designate four lectotypes from the Kellogg Collection.
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Birds are characterized by a constant body temperature, a pulmonary respiratory system, beaks, bodies covered in feathers, two legs, and two wings. Their reproduction is oviparous.Of the 178 species recorded in Galapagos, 56 are endemic and native. At present, no birds are known to be extinct in the Archipelago, but extinctions have occurred locally on some islands. For marine species distribution data cited in the CDF Galapagos Checklists refer to the five main bioregions of the archipelago (Far Northern, Northern, Western, South Eastern and the Elithabeth Bay Bioregion). For the terrestrial species the more than 120 islands, islets and small rocks have been aggregated into Islands Groups, thus, for example, the island group "Santa Cruz" includes smaller islands like Santa Fé, Plaza Norte, Plaza Sur, Baltra, Daphne Mayor, Daphne Minor, and others. Please be aware that the distribution data presented here is automatically generated from specimen records and does not always accurately reflect the known distribution for all species. IUCN red-list assessments presented here may deviate from the global IUCN list for the following reasons: -for well known species groups like vascular plants or vertebrates updates proposed to the IUCN are shown instead of the outdated, but currently accepted status; -for poorly known species groups (e.g., lichenized fungi) a general assessment is currently not possible and the list presented here is a regional red-list list for Galapagos archipelago.
Article
Abstract In this paper we describe the ectoparasitic lice (Insecta: Phthiraptera) found on 5 species of seabirds (magnificent frigatebird, great frigatebird, Nazca booby, blue-footed booby and red-footed booby) on the Galapagos Archipelago. We found 9 species of ectoparasitic lice: 5 species of Pectinopygus ischnocerans, 1 infesting each host; 2 species of Colpocephalum amblyceran lice, 1 on each frigatebird species; and 2 shared amblycerans, Eidmanniella albescens (Piaget, 1880) found on Nazca and blue-footed boobies; and Fregatiella aurifasciata (Kellogg, 1899) found on the 2 frigatebirds. We tested the relative importance and interactions of: host sex, body size, host, island, host family and breeding status and found that inter-island differences were the main predictors of prevalence and infestation intensity. These differences could be related to host density or weather, but further evidence is needed.
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The effects of colony size on individual fitness and its components were investigated in artificially established and natural colonies of the social spider Anelosimus eximius (Araneae: Theridiidae). In the tropical rain forest understory at a site in eastern Ecuador, females in colonies containing between 23–107 females had india significantly higher lifetime reproductive success than females in smaller colonies. Among larger colonies, this trend apparently reversed. This overall fitness function was a result of the conflicting effects of colony size on different components of fitness. In particular, the probability of offspring survival to maturity increased with colony size while the probability of a female reproducing within the colonies decreased with colony size. Average clutch size increased with colony size when few or no wasp parasitoids were present in the egg sacs. With a high incidence of egg sac parasitoids, this effect disappeared because larger colonies were more likely to be infected. The product of the three fitness components measured—probability of female reproduction, average clutch size, and offspring survival—produced a function that is consistent with direct estimates of the average female lifetime reproductive success obtained by dividing the total number of offspring maturing in a colony by the number of females in the parental generation. Selection, therefore, should favor group living and itermediate colony sizes in this social spider.
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Colonially nesting Cliff Swallows (Passeriformes: Hirundo pyrrhonota) in southwestern Nebraska, USA, are commonly parasitized by hematophagous swallow bugs (Hemiptera: Cimicidae: Oeciacus vicarius) and fleas (Siphonaptera: Ceratophyllidae: Ceratophyllus celsus). We examined to what degree these ectoparasites represent a cost of coloniality for Cliff Swallows. The number of swallow bugs per nest increased significantly with Cliff Swallow colony size. Body mass of nestling swallows at 10 d of age declined significantly as the number of bugs per nestling increased. By fumigating half of the nests in some colonies, killing the bugs, and leaving half of the nests as nonfumigated controls, we showed that swallow bugs lower nestling body mass and nestling body mass and nestling survivorship in large Cliff Swallow colonies but not in small ones. Bugs cost nestlings, on average, up to 3.4 g in body mass, and reduced survivorship by up to 50%. Parasitism by fleas showed no consistent relationship with colony size during the nestling period but increased significantly with colony size early in the season, when birds were first arriving in the study area. Flees did not affect nestling body mass or survivorship and thus, unlike swallow bugs, are probably not important costs of coloniality to Cliff Swallows. Field observations and nest fumigation experiments showed that Cliff Swallows apparently assess which nests are heavily infested with swallow bugs early each spring and select parasite-free nests, leading sometimes to alternate-year colony site usage. Cliff Swallows were more likely to construct new nests (rather than reusing old ones) in large colonies than in small colonies, probably in response to heavier infestations of ectoparasites in the existing nests of large colonies.
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Although some parasites have obvious pathogenic effects, others appear to have subtle, indirect effects that are poorly understood, particularly in natural populations. Indirect effects may result from parasites altering host metabolic rate and hence host energy needs, yet no experimental studies have shown this to be the case for non-laboratory hosts. We report the results of a long-term field experiment designed to test the impact of parasites on host energetics. We measured the energetics of feral rock doves (Columba livia) with populations of feather-feeding lice, traditionally considered to have little or no effect on host fitness. The lice reduced feather mass leading to increased thermal conductance and metabolic rate, as well as a steady reduction in host body mass over the course of the nine-month study. Our results demonstrate that even classically `benign' parasites such as feather lice can reduce host condition through the accumulation of subtle energetic costs over time. We argue that experimental manipulations are a prerequisite for documenting such effects.
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Few field studies have evaluated whether ectoparasites affect the long-term survival of their adult host, although many studies have examined the impact of parasites on the host's offspring. In the colonially nesting cliff swallow (Hirundo pyrrhonota), we manipulated ectoparasite load (of cimicid bugs, fleas, and chewing lice) by fumigating adults and comparing annual survivorship of fumigated birds and non-fumigated control birds captured at the same time. Mark-recapture experiments over an 8-year period revealed that non-fumigated birds had an annual survivorship about 12% less than that of fumigated birds, on average, but the effects did not vary with colony size. Based on the difference in survivorship between fumigated and non-fumigated birds, we estimated that parasitized individuals had an annual survivorship of 0.38, compared with 0.57 for non-parasitized birds. The parasite-caused reduction in survivorship was the equivalent of the host losing up to one year of lifetime reproductive success. Ectoparasites did not preferentially infest hosts of lower quality, suggesting that all birds in the population were at potential risk of suffering parasitism and the resulting reductions in survivorship. Our results show that obligate ectoparasites such as fleas and lice impose a substantial long-term cost to their hosts and suggest that future studies of ectoparasitism should consider the parasites' effect on annual survival of adult hosts.
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This study documents patterns of variation in abundance and prevalence of Docophorulus capillatus (Insecta: Ischnocera, Philopteridae) on the crown feathers of Pied Flycatchers Ficedula hypoleuca in relation to host sex, age, survival, physical condition, expression of secondary sexual traits and genetic relatedness. Louse populations were relatively stable over a S-year period, with low prevalences in the range 15-30%. Pair mates had similar louse loads, indicating the possible role of direct contact between birds as an agent of louse dispersal. Females were consistently more heavily and frequently infested than males at almost all ages. Louse prevalence and abundance tended to decrease or oscillate with advancing age, with a major peak late in life which was much more marked in females; no surviving birds older than five years had lice on their crown. Although bird condition in a given year seemed not to be affected by louse infestations, there were decreases in individual condition between years which were linked to increases in louse infestations in females. Individual birds of both sexes had similar louse loads in successive years. Within-family resemblance in louse loads was only detected between mothers and daughters and, to a lesser extent, between females and their male offspring. We discuss different hypotheses to account for intersexual differences in parasite infestation.
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Conspicuous secondary sexual traits may have evolved as handicap-revealing signals or as badges of status. We present results of an experiment using males of the sexually dimorphic house sparrow (Passer domesticus), that support the idea that the male-specific bib can be both a handicap-revealing signal and a reliable badge indicating the physical condition of the bird. In a test of the immunocompetence handicap hypothesis, wild-caught adult male house sparrows were studied in captivity. Birds implanted with elevated doses of testosterone were more dominant, had higher circulating levels of both testosterone and corticosterone and they also harboured relatively larger ectoparasite loads. Higher parasite loads were also associated with individuals showing lower immunocompetence and larger changes in bib size. A new model for immunocompetence effects in sexual selection is introduced, integrating actions that the hypothalamopituitary axis exerts on gonads, adrenals and the thyroid gland. The ”integrated immunocompetence model” synthesizes both the ”handicap” (i.e. survival-decreasing) and ”badge of status” (i.e. survival- enhancing) models for evolution of secondary sexual traits.
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The hypothesis that cooperative breeding entails a cost in terms of transmission of ectoparasites was tested by a comparative analysis among sympatric Australian passerines. The general trend found using the allometry method and outgroup analysis indicates that contagious ectoparasites are not more common on cooperatively breeding than on non-cooperatively breeding hosts. Body weight, migratory patterns and relative abundance of hosts are factors far more important than cooperative breeding that affect the levels of ectoparasitism in the host genera studies. Ectoparasitism increases with host body weight and relative adundance, while sedentary host genera tended to show less hippoboscid fly diversity than migratory host genera. There is an interaction between breeding system and migratory pattern when relative density of contagious ectoparasites (i.e. mites, ticks and bird lice) is considered: the number of contagious ectoparasites per host is larger on cooperatively breeding host genera than on non-cooperatively breeding host genera among sedentary passerines, but the trend is reversed for migrant passerines.
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Without genetic tests of parentage, descriptions of mating systems must be considered hypothetical. Here we confirm the existence of cooperative polyandry in the Galapagos hawk (Buteo galapagoensis) using multilocus minisatellite DNA fingerprinting. In this species, breeding groups consist of one adult female and from one to eight males (the modal number of males is two). In polyandrous groups, all males copulate with the female and participate in the provisioning of the young. DNA samples from 66 individual hawks from ten breeding groups on the island of Santiago revealed mixed paternity in most groups. Multiple paternity was detected in five of six groups that produced two chicks in one breeding attempt (year). In addition, different males sired young in consecutive years in five of six groups in which male group membership was constant. Patterns of paternity suggest that reproductive success was randomly distributed among males within groups, with males apparently having equivalent probabilities of siring each young. Analysis of genetic similarity indicates that males within groups were typically not close relatives These results demonstrate that the mating system of the Galapagos hawk is polyandrous, with relatively egalitarian relations among unrelated males belonging to the same breeding group.
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The pattern of parasitism of the flea species Xenopsylla dipodilli and Nosopsyllus iranus theodori on the desert rodent species Gerbillus dasyurus was studied to test the hypothesis that the relationships between flea abundance and host density conform to pre-existing models of R. M. Anderson and R. M. May, with the correction that the density of those host individuals that possess permanent burrows (residents) is substituted for the overall host density. It was predicted that: (1) the intensity of flea infestation would increase in curvilinear fashion with increase of host density to a plateau that would be attained at a lower level of host density than would be expected from the basic model, and (2) the prevalence of flea infestation plotted against host density would be hump-shaped. The results indicated that intensity of flea infestation increased in either curvilinear fashion to an asymptote (for X. dipodilli) or linearly (for N. i. theodori) with increase of host density. As host density increase
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1. We test the hypothesis that avian social system (territorial vs, colonial) has an impact on the ecological characteristics of avian lice. We compared the louse loads of two congeneric host species, the territorial hooded crow (Coitus corone cornix L.) and the colonial rook (C. frugilegus L.). Each species harboured the same five genera of lice; one species of louse was shared, while the other four species on each host were host-specific. 2. More rooks harboured Myrsidea, Philopterus, Brueelia and Allocolpocephalum spp, than crows. 3. Rooks harboured more species-rich louse loads than crows, 4. Louse loads were also more diverse on rooks than on crows, 5. The frequency distributions of lice on rooks were less aggregated than on crows, 6. Sex ratios of lice were less biased on rooks than on crows. Biased sex ratios were correlated with the subpopulation size of lice on individual hosts, making it necessary to control for subpopulation size in comparative analyses, 7. These findings may result from the increased frequency of horizontal transmissions via increased body-to-body contacts among colonial rooks, compared to territorial hooded crows.
Article
Interspecific variation in sexual size dimorphism has commonly been attributed to variation in social mating system, with dimorphism increasing as intrasexual competition for mates increases. In birds, overall body size has also been found to correlate positively with size dimorphism. In this study, we describe variation in morphology and mating system across six populations of the endemic Galápagos Hawk (Buteo galapagoensis). Galápagos Hawks exhibit cooperative polyandry, a mating system in which long-term social groups contain a single female and multiple males. Comparisons among islands revealed significant differences in overall body size for both adults and immatures. Populations ranged from completely monogamous to completely polyandrous, with varying mean group sizes. Data did not support our prediction that sexual size dimorphism would increase with the degree of polyandry (number of males per group) or with body size; there was no correlation between mating system and sexual dimorphism. We did find a significant negative relationship between degree of polyandry and body size among islands, opposite of the pattern predicted. Variación en Morfología y Sistema de Apareamiento entre Poblaciones de Buteo galapagoensis Resumen. Variación interespecífica en dimorfismo sexual ha sido atribuída comúnmente a variaciones del sistema social de apareamiento, de tal manera que el dimorfismo aumenta conforme aumenta la competencia intrasexual por parejas reproductivas. También se ha encontrado que el tamaño corporal se correlaciona positivamente con el dimorfismo. En este estudio describimos la variación morfológica y el grado de poliandría de seis poblaciones de Buteo galapagoensis, una especie que exhibe un sistema de apareamiento denominado poliandría cooperativa. En este sistema los grupos de individuos reproductivos incluyen una sola hembra y múltiples machos. Se comprobó que existen diferencias significativas en el tamaño del cuerpo de adultos y juveniles entre islas. Las poblaciones muestreadas variaron entre monógamas y completamente poliándricas, y el tamaño promedio de los grupos fue variable. Los datos no apoyaron las predicciones establecidas inicialmente pues el grado de dimorfismo sexual no aumentó con el nivel de poliandría (número de machos por grupo) ni con el tamaño corporal, ni hubo una correlación entre el sistema de apareamiento y el dimorfismo sexual. La relación entre el tamaño corporal y el sistema de apareamiento fue contraria a la que se predijo: hubo una correlación negativa significativa entre el grado de poliandría y el tamaño corporal entre islas.
Article
Many animal species live and breed in colonies. Although biologists have documented numerous costs (increased competition for limited resources) and benefits (more pairs of eyes to watch for predators) of group living, they often still do not agree on why coloniality evolved in the first place. Drawing on their 12-year study of a population of cliff swallows in Nebraska, USA, the authors investigate 26 social and ecological costs and benefits of coloniality. They explore how these costs and benefits are reflected in reproductive success and survivorship, and speculate on the evolution of cliff swallow coloniality. This study of vertebrate coloniality should be of interest to all who study social animals, including behavioural ecologists, population biologists, ornithologists and parasitologists. Its focus on the evolution of coloniality should also appeal to evolutionary biologists and to psychologists studying decision making in animals. The authors' research on swallows was the subject of an award-winning exhibition at the Peabody Museum of Natural History in New Haven, Connecticut, and was included in the BBC television production, "The Trials of Life".
Article
The numbers of chewing lice were determined for adult bee-eaters and related to different measures of breeding density. Bee-eaters are infested by three species of chewing lice (Meropoecus meropis, Meromenopon meropis and Brueelia apiastri). Meropoecus meropis is the most common species and 94% of all adult bee-eaters were infested. This species also shows a significant variation between colonies, namely, infestation rate increases with colony size. Using different measures to describe colony size, a stepwise regression analysis showed that inter-nest distance is the best predictor for ecoparasite load. Average infestation rate per individual decreased significantly with increasing inter-nest distance. This relationship was even more pronounced for the maximum number of parasites found within a colony and with the variation in parasite load among members of a colony (controlling for number of breeding pairs). There was no difference in ectoparasite load between the sexes and no general patterns related to the position of the breeding site within the colony.
Chapter
The last ten years have seen an enormous increase in the understanding of the role that parasites and pathogens play in the regulation of host abundance. Primarily, this progression has been stimulated by the theoretical framework developed to examine the population dynamics of parasite—host relationships by Anderson and May (1978, 1979, 1982) and May and Anderson (1978, 1979). These models have been extended to examine the dynamics and control of a wide range of parasites from schistosomiasis (Crombie and Anderson, 1985) and other parasitic helminths of man (Anderson 1982; Anderson and May 1985), through to the parasitic helminths of domestic livestock (Smith 1984; Grenfell et al., 1987). Although considerable empirical data has accumulated from studies of free-living host—parasite communities, there have been few attempts to interpret this mass of data in terms of the models developed for simple one host, one parasite ‘communities’. In part, this enigmatic divergence between empirical data and theoretical understanding may stem from hierarchical differences in the levels of complexity between the majority of empirical data and that of the models (Table 10.1). This chapter attempts to partly redress this balance by showing how the Anderson and May models can be extended to consider the dynamics of more complex parasite—host communities.
Article
1. Data are presented comparising the first quantitative survey of lice from Neotropical birds. The data were collected in the Andean foothills of south-eastern Peru using a novel scheme for quantitative sampling of ectoparasites from freshly killed hosts. 2. In total, 685 birds representing 127 species in 26 families were sampled for lice; 327 (47.7%) birds were parasitized, with a mean intensity of 6.6 lice per bird and a mean richness of 1.1 louse species per host species. 3. The bulk of variation in louse load was among host species nested within genera, although some variation occurred at higher taxonomic levels. 4. Lice were extremely host-specific; nearly all species were restricted to a single species of host (monoxenous). 5. Thirteen metapopulations of lice (10%) had significantly skewed sex ratios, of which four were skewed toward males, representing the first male-biased sex ratios reported for chewing lice. Thirty-four metapopulations (27%) had significantly skewed age ratios and showed an overall bias toward adults. 6. Results are discussed in relation to current life-history theory and are compared with the findings of a recent survey of lice from temperate-zone birds. Tropical lice are neither more speciose nor more abundant than temperate-zone lice, which is consistent with the view that the environment for chewing lice is delimited by the body of the host rather than by `external' conditions. 7. Non-quantitative host--parasite records are reported for lice collected from an additional 75 birds representing 45 species in 20 families.
Article
The purpose of this study was to determine the relationship in timing of important stages of the life cycles of mallophagen lice and the cycles of the subspecies of the Orange-crowned Warbler (Vermivora celata) which they parasitize. The timing of breeding in the mallophagans Ricinus picturatus and Menacanthus sp. coincides with the timing of breeding in the subspecies of host warbler, resulting in sufficient numbers of lice for transfer to the newly available juvenal warbler hosts. No eggs are laid during the periods of avain molt; any eggs present would be lost with the feathers as they are dropped. Breeding is very limited in the winter when reproductive effort would be wasteful; opportunities for dispersal are rare at this time, and birds are extremely efficient at keeping their numbers of lice at a minimum. Several lines of evidence suggest that the timing of breeding in R. picturatus and Menacanthus sp. is controlled by the reproductive hormones of V. celata. Hormones are available to these lice with feed on the blood of their host. Peak breeding in the louse populations coincides with peak production of reproductive hormones in avian populations and lasts only as long as the breeding season of the subspecies parasitized. Juvenal birds which are not producing great quantities or reproductive hormones never carry louse eggs. During the fall molt periods, the gonads are in a refractory state and produce a minimum amount of reproductive hormones. During the late fall and in mild winters, birds frequently exhibit some reproductive behavior which accounts for the limited egg laying by lice at this time. Though hormone production may be moderately high during the winter, release to the blood is usually restricted. Members of the mallophagan genus Philopterus normally do not feed on blood, and in this group the life cycle is not so closely coordinated with that of the Orange-crown.
Article
In cooperative breeding systems, males that share a nest face the prospect of providing for young that are not their own. Males of many species attempt to reduce the risk of losing paternity with aggressive behaviors, thereby limiting other males' access to the female during copulation. The Galapagos Hawk (Buteo galapagoensis) exhibits an extreme form of cooperative polyandry in which anecdotal data suggest all males in a territory share mating equally with the female, with very little to no interference, and care for young within the group. Males in a territory are unrelated adults and share paternity. We examine paternal care in relation to the shared parentage of the Galapagos Hawk and offer explanations for group cohesion. We found that paternal care was variable and that all males cared for the young on their territory without regard to the number of males residing together. There was evidence that males that sired young and those that sired none did not differ in quantity of care. However, we could not rule out a relationship between paternity and care. There was no obvious cue the males could use to discern paternity, since the only evidence of dominance was a subtle hierarchy expressed in larger groups. We suggest that the simple rule for paternal care in the Galapagos Hawk is that ifa male is a group member, he will copulate with the female, have some probability to fertilize the eggs, and provide care for young produced at the nest.
Article
In a 4-yr study, I investigated the costs of coloniality for two species of squirrels (Sciuridae) : loosely colonial White-tailed Prairie Dogs (Cynomys leucurus) and densely colonial Black-tailed Prairie Dogs (C. ludovicianus). Study sites were in Wyoming and Colorado (White-tails) and Colorado and South Dakota (Black-tails). By an examination of both intra- and interspecific effects, four costs were investigated: (1) increased aggression, (2) increased transmission of diseases and ectoparasites, (3) increased probability of misdirected parental care resulting from the mixing of unrelated young, and (4) increased conspicuousness to predators. The possibility of various miscellaneous costs was also investigated. I hypothesized that the costs of coloniality should be greater (a) for individuals of large wards (subcolonies) than for individuals of smaller wards and (b) for Black-tails than for White-tails. Isolated individuals of either species were never observed. To measure aggression, most of which was probably related to competition for mates and nesting burrows, I recorded fights, chases, and other hostile interactions. Three lines of circumstantial evidence indicated that this sort of aggression was deleterious to individual prairie dogs. For both White-tails and Black-tails, aggression per individual per h correlated positively with ward size. Aggression was not more pronounced for Black-tails than for White-tails, but interspecific comparisons were difficult because aggression in the two species was manifested differently. White-tails and Black-tails are both extremely susceptible to sylvatic plague, but intra-or interspecific investigations of the transmission of this disease were not possible. I measured ectoparasitism by sampling for fleas at burrow entrances and by counting fleas and lice on the adults and young themselves. Four lines of circumstantial evidence indicated that ectoparasites were deleterious to their prairie dog hosts. For both White-tails and Black-tails, the number of fleas per burrow entrance correlated positively with ward size. Counts from burrow entrances and from the animals themselves both indicated that ectoparasitism was probably more costly for Black-tails than for White-tails. Both White-tail and Black-tail young mingled regularly with young from different litters shortly after their first emergences from the natal burrows, with Black-tail young tending to mingle sooner. Experiments involving the transfer of colour-marked young into foster litters indicated that mixing of unrelated young, with the possible consequence of misdirected parental care, was probably not seriously deleterious for parents of either species. Vocal conspicuousness was measured by recording the rate of territorial calling, and visual conspicuousness was measured by counting numbers of visible mounds and numbers of visible prairie dogs. Both vocal and visual conspicuousness correlated positively with ward size for both White-tails and Black-tails. Further, both types of conspicuousness were more pronounced for Black-tails than for White-tails. Neither vocal nor visual conspicuousness could be measured on a per-individual basis, and an assessment of associated costs was therefore difficult. In summary, I conclude that there are probably several costs associated with prairie dog coloniality, that the severity of some of the costs correlates positively with colony or ward size for both White-tails and Black-tails, and that some of the costs are probably more pronounced for Black-tails than for White-tails.
Article
Although Colinus virginianus coveys may not be cohesive in some parts of the range or during some seasons, in the sedentary populations of N Florida, young of the year may retain covey membership until the breeding season. Among these birds, there were found nonrandom associations between intensity and covey size for some parasitic helminths. This was most consistently true for the monoxenous parasite with the shortest life cycle. -from Authors
Article
The size of groups formed by social animals is thought to result from a combination of selection pressures acting on individuals to maximize their fitness. In addition to commonly-invoked selective agents (e.g., predation), a growing number of studies suggest that levels of parasitism may be related to host group size and that parasites may influence optimal group size. We used a meta-analysis to quantify the intraspecific association found in published studies between prevalence and intensity of parasitism and host group size in a variety of taxa. We considered separately contagious parasites, which are transmitted via contact with infected individuals or feces, and mobile parasites which do not need proximity among hosts for transmission. In addition to mode of transmission, host group mobility was examined as a potential correlate of the association. Consistent positive correlations were found between host group size and both the prevalence and intensity of contagious parasites. By contrast, the intensity of infection by mobile parasites consistently decreased as host group size increased. Host group mobility had no apparent effect on either the strength or the direction of these correlations. Although few experimental studies examined the causal effect of parasitism on host group size, strong circumstantial evidence was provided, at least for mobile parasites, by many reports of larger host group sizes following increases in parasite abundance. Our results therefore suggest that parasites with different modes of transmission can exert conflicting selection on host group size. The trends found in the meta-analysis, however, do not hold in interspecific comparative studies, possibly owing to differences among related species in the relative importance of parasitism as a selective force.
Article
An overview of the extensive and frequently controversial literature on communally breeding birds developed since the early 1960s, when students of evolution began to examine sociality as a product of natural selection. Jerram Brown provides original data from his own theoretical and empirical studies and summarizes the wide array of results and interpretations made by others.Originally published in 1987.The Princeton Legacy Library uses the latest print-on-demand technology to again make available previously out-of-print books from the distinguished backlist of Princeton University Press. These paperback editions preserve the original texts of these important books while presenting them in durable paperback editions. The goal of the Princeton Legacy Library is to vastly increase access to the rich scholarly heritage found in the thousands of books published by Princeton University Press since its founding in 1905.
Article
We present a simple, accurate method for quantifying the ectoparasite loads of live birds in the field. Birds were dusted with pyrethrin to irritate their ectoparasites, which were then dislodged from the plumage by ruffling the feathers over a collecting surface for repeated timed bouts until the point of diminishing returns was reached. This method re- quired less equipment and was more accurate and efficient than previously described meth- ods, as we show by comparing our method to other popular approaches. Dust-ruffling is best suited for sampling "permanent" ectoparasites, such as chewing lice (Insecta: Phthiraptera), which pass their entire life cycle on the body of the host. SACUDIDAS DE POLVO: UN METODO SENCILLO PARA CUANTIFICAR LAS CARGAS DE ECTOPARASITOS EN AVES VIVAS Sinopsis--Presentamos un mtodo sencillo y preciso para cuantificar las cargas de ectopar- 'sitos de aves vivas en el campo. Se polvorea las aves con pyrethrina para irritar los ectopar- 'sitos, los cuales son removidos del plumaje al agitar las plumas sobre una superficie de colecci6n en ocasiones consecutivas hasta que se 11egue al punto de cargas menores. Este mtodo requiere menos equipo y es m's preciso y eficiente que mtodos previamente des- critos, lo cual evidenciamos al comparar nuestro mtodo con otros mtodos comunes. Las sacudidas de polvo es ms apropiado para muestrear ectopar'sitos permanentes, tales como Phthiraptera, que pasan su ciclo deda completo en el cuerpo del hospedero.
Chapter
This is a major synthesis of the theory and empirical knowledge about the ecology and epidemiology of infectious diseases in natural, unmanaged, animal and plant populations. Throughout the book a dialogue is developed between the patterns observed in empirical studies of disease in natural populations and the mathematical models used to dissect and examine the observed epidemiological patterns. The book arose from a symposium at the Newton Institute at Cambridge University. It is divided into a number of reviews by experts in various fields and four group reports: two of these synthesize important issues relating to the dynamics of microparasites and macroparasites, while the others discuss spatial patterns in disease dynamics and the evolutionary biology of parasites, pathogens and their hosts.
Book
Cooperative breeding is an unusual kind of social behaviour, found in a few hundred species worldwide, in which individuals other than the parents help raise young. Understanding the apparently altruistic behaviour of helpers has provided numerous challenges to evolutionary biologists. This book includes detailed first-hand summaries of many of the major empirical studies of cooperatively breeding birds. It provides comparative information on the demography, social behaviour and behavioural ecology of these unusual species and explores the diversity of ideas and the controversies which have developed in this field. The studies are all long-term and consequently the book summarises some of the most extensive studies of the behaviour of marked individuals ever undertaken. Graduate students and research workers in ornithology, sociobiology, behavioural ecology and evolutionary biology will find much of value in this book.
Article
Fourteen species of Colpocephalum sen. lat. from gallinaceous birds are recognized and discussed. Ten of these are newly described; they and their type-hosts are chloropi (Tropicopcrdix chloropus), talegallae (Talegalla cuvicri), orientalis (Arborophila oricntalis sumatrana), tetraophasis (Tctraophasis obscurus), freycineti (Mcgapodius freycinet freycinet), lathami and aleclurae (Alectura lathami lathami), wilhelmi and arfakiani (Aepypodius arfakianus), and maleonis (Macrocephalon maleo). C. echinatum Ewing is synonymized with C. thoracicum Kellogg and Paine. C. parumpilosum Piaget and C. hoffmanni Zavaleta are considered species sedis incertae. A key to the species is given.
Article
The frequency distribution of parasites among hosts is used as the basis of the quantitative assessment of the nature of parasitism. The host–parasite system is regarded as an ecological relationship between populations of two different species of organisms. From the overdispersed frequency distributions exemplified by the Negative Binomial distribution a specially truncated form is derived and shown to fit the data of Hynes & Nicholas (1963). The theoretical consequences are discussed and these form the basis of a definition of parasitism. I am indebted to Professor H. B. N. Hynes who so readily understood my general aims and freely provided detailed information about his work. I also have great pleasure in thanking Professor John H. Whitlock, not only for the original computing facilities which he so generously provided, but also for his many other kindnesses. I am also very grateful to Dr Charles Henderson Jun. for his work on the original computer program and to Dr Mark Westwood for his ingenuity and labours in producing a new approach to the computations.
Article
(1) Three categories of biological processes are shown to have a destabilizing influence on the dynamical behaviour of model host-parasite associations: parasite induced reduction in host reproductive potential, parasite reproduction within a host which directly increases parasite population size and time delays in parasite reproduction and transmission. (2) The importance of parasitic species as regulators of host population growth is examined in light of empirical evidence. Data from two particular laboratory studies used to indicate the magnitude of this regulatory influence. Suggestions are made concerning the type of information required from field studies to facilitate critical assessment of theoretical predictions.
Article
(1) Several models describing the dynamics of host-parasite associations are discussed. (2) The models contain the central assumption that the parasite increases the rate of host mortalities. The parasite induced changes in this rate are formulated as functions of the parasite numbers per host and hence of the statistical distribution of the parasites within the host population. (3) The parameters influencing the ability of the parasite to regulate the growth of its host's population, and the stability of parasite induced equilibria, are examined for each model. (4) Three specific categories of population processes are shown to be of particular significance in stabilizing the dynamical behaviour of host-parasite interactions and enhancing the regulatory role of the parasite. These categories are overdispersion of parasite numbers per host, nonlinear functional relationships between parasite burden per host and host death rate, and density dependent constraints on parasite population growth within individual hosts.
Article
Lice (Insecta: Phthiraptera) are often considered a model group of parasites for studies of cospeciation because of their high host specificity, and louse species in the genus Brueelia are relatively host-specific. To test the extent of cospeciation, we reconstructed a phylogeny for Brueelia from nuclear (EF1 a) and mitochondrial (COI) DNA sequences. This phylogeny was generally well resolved and supported. Two major clades within Brueelia (as well as several other lineages) were identified, and these corresponded to major morphological differences in the preanten-nal region of the head and sclerotization of the abdomen. However, the phylogeny of Brueelia showed little concor-dance to a published phylogeny of the hosts. In addition, we uncovered four cases (out of 15 species) of one species of Brueelia on two or more bird species. We argue that the high dispersal capabilities of Brueelia species, e.g. phoresis on hippoboscid flies, are a likely explanation for the incongruence between host and parasite phylogenies in this case.
Article
Most reports of interactions between feather mites and their avian hosts have assumed that mites have detrimental effects on their hosts, i.e. that they behave as parasites. We investigate the effects of feather mites Gabucinia delibata on the body condition of Red-billed Choughs Pyrrhocorax pyrrhocorax, a highly social, medium-sized corvid species. Feather mites were absent in fledglings al the nest and were probably acquired by Choughs from 1 to 5 months after fledging, when they joined communal roosts. The abundance of feather mites on both wing and tail increased with age and development of social habits in non-breeding Choughs, but decreased when they reached breeding status. Mated Choughs had similar abundances of feather mites. The abundance of mites correlated positively with body condition (computed as the residuals of mass on a ''size factor'') in both males and females, and body condition was in general better for Choughs holding mites than for those lacking mites. The conclusion that feather mites do not have detrimental effects on Choughs was reinforced by the fact that feather mite abundance did not differ between Choughs with normal and crossed bills, respectively, suggesting that preening does not remove mites from the feathers. This particular association thus could be labelled as non-parasitic, suggesting at least a commensal, and possibly a mutualistic relationship. In the latter case, the hypothesised benefits accrued to Chough hosts from their association with mites may derive from an improved feather cleaning, and from the supposed protection against pathogenic organisms achieved primarily by preemption of resources by more benign species, such as feather mites.
Article
The Galapagos Hawk Buteo galapagoensis is one of few species showing cooperative polyandry. As many as four males may mate with one female and share a territory and nest, Such groups, on average, produce more young than monogamous pairs, but on a per male basis (assuming that each male of a group has an equal chance to fertilize each young) polyandrous males produce fewer young per year than monogamous males. Territorial breeding birds show higher yearly survivorship (90%) than non-territorial, non-breeding birds (50% or less). All territorial birds seem to remain on their territories for life, and monogamous pairs actually constitute the remnants of polyandrous groups. Some potential factors producing such an unusual system are discussed. Limited breeding space and high mortality among non-territorial birds seem to work in favour of group breeding in this and other cooperative species. Polyandry may be favoured because of the reduced value of extra females in hawk breeding behaviour. Equal-status males may occur because of the lack of kinship among cooperating males and the high potential genetic cost of being a helper in a long-lived, low fecundity species. Other possible factors favouring group breeding are territory acquisition and the variable nature of the Galapagos climate.
Article
Over three thousand live birds have been examined in the British Isles and Sweden in a study of the ecology and biology of their ectoparasites. The main emphasis has been placed on Mallophaga, which are discussed in this paper. The very exact food and temperature requirements of feather lice are considered. The effect of lice on the host is discussed. Sick or injured birds which are unable to rid themselves easily of parasites tend to develop heavy infestations. The relationship between host and parasite is described. The infestation of five common bird species is analysed on a specific and monthly basis. The proportion of birds carrying various species of lice varies from species to species and from month to month and also between sexes. There is a peak of infestation prior to the bird's breeding season. Rates of infestation on autumn migrants in Sweden are discussed. Birds found uninfested and later found to be infested appear to acquire a parasite population at any season of the year. The habitat of Mallophaga on their hosts is given for each species examined at Silwood Park, Berkshire. The following points are discussed in appendices:–the collection and examination of birds, and an attempt to develop a satisfactory technique for sampling Mallophaga populations.
Article
The number of a common parasite (Cuclotogaster sp.) on male satin bowerbirds was related to male mating success in a test of Hamilton and Zuk's (1982) bright male hypothesis. The data do not show the expected inverse correlation between female mating preferences and the level of parasitic infection of males predicted by that model. Nearly all matings are accomplished by bower-holding males (Borgia 1985a), but the vast majority of these males were uninfected. There were large differences in mating success among the uninfected bower holders, but this could not be explained by between male differences in the level of parasitic infection. From this I conclude that levels of parasitic infection are not now an important direct cause of intermale variation in mating success. The results are, however, consistent with a hypothesis that a low level of infection is indicative of the overall healthy condition of a male. If this is true, it supports the hypothesis that the ability to hold a bower may be an indicator of male condition to females.
Article
Hamilton and Zuk proposed that bright male plumage may have evolved in males of polygynous species as a result of female pre