Consequences of information use in breeding habitat selection on the evolution of settlement time

ArticleinOikos 124(1) · September 2014with 127 Reads
Abstract
The role of temporal changes and spatial variability in predation risk and prey's means of mitigating such risks is poorly understood in the context of potential threats of global climate change for migratory birds. Yet nest predation, for example, represents a primary source of reproductive mortality in birds. To assess risk birds must spend time prospecting potential breeding sites for cues or signals of predator presence. However, competition for breeding sites with advantage to prior residency poses an evolutionary dilemma as individuals also benefit from early settling. We develop a model to examine adaptive prospecting time for predator cues on breeding grounds characterized by spatial heterogeneity in nest predation risk. We study how populations respond to environmental change represented by variation in habitat specific levels of nest predation, habitat composition, population vital rates, and availability of information (via prospecting) in the form of acoustic predator cues. We identify two mechanisms that regulate and buffer impacts of environmental change on populations. First, the adaptive response to lower population abundance under deteriorating environmental conditions is to increase prospecting time, which in turn increases individuals nest success to counteract population declines. This occurs because reduced competition for sites decreases the benefit of early settlement. Second, per capita success in site choice increases during population declines owing to reduced competition that increases the availability of good sites. We also show that the increased benefit to settling early when competition increases can lead to the paradoxical result that with greater spatial heterogeneity, less effort is placed on discerning good and bad sites. Our analysis thus contributes several novel results by which nest predation, settlement phenology, prospecting time and information gathering can influence species capacity to adapt to changing environments.

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  • ... For example, those used by information producers or scroungers (Doligez et al. 2003), strategies which may be contingent on success or the fidelity of conspecifics (Pärt et al. 2011), and different strategies based on the effort (e.g. time) invested in collecting information which will depend on the intensity of competition for breeding sites (Schmidt et al. 2015). One potentially fruitful approach to look beyond individual strategies is through the analogy of choosing a coloured ball (or balls at the population level) from an urn under the constraint that sampling is without replacement and (i.e. ...
    ... choice of breeding site) is biased. Information from pre-or post-and personal or conspecific breeding cues, or any inherent preference, is reduced to sampling bias (Schmidt et al. 2015). This approach is amenable to a game-theoretical analysis of breeding habitat selection that extends to investigating the ecological and evolutionary consequences of environmental change. ...
    ... For example, as population densities decline in degraded environments individuals are expected to invest more time in information gathering and exhibit greater bias toward selecting good sites. This suggests that information-gathering strategies have the capacity to ameliorate environmental change (Schmidt et al. 2015). ...
    Article
    Full-text available
    Nest predation is a key source of selection for birds that has attracted increasing attention from ornithologists. The inclusion of new concepts applicable to nest predation that stem from social information, eavesdropping or physiology has expanded our knowledge considerably. Recent methodological advancements now allow focus on all three players within nest predation interactions: adults, offspring and predators. Indeed, the study of nest predation now forms a vital part of avian research in several fields, including animal behaviour, population ecology, evolution and conservation biology. However, within nest predation research there are important aspects that require further development, such as the comparison between ecological and evolutionary an-tipredator responses, and the role of anthropogenic change. We hope this review of recent findings and the presentation of new research avenues will encourage researchers to study this important and interesting selective pressure, and ultimately will help us to better understand the biology of birds.
  • ... By sampling their environments (e.g., patches, mates, habitats ) and subsequent links to performance (prey harvest rates, offspring production), organisms often both use and produce information about their environment, which in many cases is publicly available (Danchin et al. 2004 ). Social information use is likely a pervasive and important process in ecology and evolution that affects species' population growth and persistence (e.g., Doligez et al. 2003; Schmidt et al. 2015b ). However, the degree to which feedbacks occur between population growth and social information are not well explored. ...
    ... Based on the above assumptions, we conceptualize a population of individuals that settle sites sequentially based on the availability of options and information available. The Wallenius hypergeometric distribution (henceforth, WHGD; Fog 2008; Schmidt et al. 2015b ) provides an analytically tractable approach to determine per capita population growth rates based on informed habitat selection. The WHGD is similar to the more familiar hypergeometric distribution, however, the former takes into account unique biases assigned to the different objects that are sampled. ...
    ... Assuming X obs is independent of habitat type, the odds ratio is determined by fledgling rates, detection rates, or both. Competition over sites could negatively affect X obs through frequency-dependent selection, and this model is amenable to a game theoretical approach (Schmidt et al. 2015b). However, at the end of the breeding, there is little competition for breeding sites. ...
    Article
    Full-text available
    Social information is used widely in breeding habitat se- lection and provides an efficient means for individuals to select hab- itat, but the population-level consequences of this process are not well explored. At low population densities, efficiencies may be reduced be- cause there are insufficient information providers to cue high-quality habitat. This constitutes what we call an information-mediated Allee effect. We present the first general model for an information-mediated Allee effect applied to breeding habitat selection and unify personal and social information, Allee effects, and ecological traps into a com- mon framework. In a second model, we consider an explicit mech- anism of social information gathering through prospecting on con- specific breeding performance. In each model, we independently vary personal and social information use to demonstrate how dependency on social information may result in either weak or strong Allee ef- fects that, in turn, affect population extinction risk. Abrupt transitions between outcomes can occur through reduced information transfer or small changes in habitat composition. Overall, information-mediated Allee effects may produce positive feedbacks that amplify population declines in species that are already experiencing environmentally driven stressors, such as habitat loss and degradation. Alternatively, social in- formation has the capacity to rescue populations from ecological traps.
  • ... However, the frequency- dependent advantage for an individual to preempt space, such as a breeding territory, earlier than its competitors can have a significant impact on both population and evo- lutionary dynamics (Day and Kokko 2015). For example, Schmidt et al. (2015b) showed that such a preemptive advantage results in reduced levels of information gathering commensurate with population size. However, when this preemptive advantage relaxes due to declining demographic rates (e.g. ...
    ... As a result, the ESS (i.e. evolutionarily stable strategy) probability of obtain- ing a good territory increases within a deteriorating habi- tat ( Schmidt et al. 2015b). Hence, information-gathering may be an important evolutionary mechanism buffering populations from further declines. ...
    Article
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    Despite the wide usage of the term information in evolutionary ecology, there is no general treatise between fitness (i.e. density‐dependent population growth) and selection of the environment sensu lato. Here we 1) initiate the building of a quantitative framework with which to examine the relationship between information use in spatially heterogeneous landscapes and density‐dependent population growth, and 2) illustrate its utility by applying the framework to an existing model of breeding habitat selection. We begin by linking information, as a process of narrowing choice, to population growth/fitness. Second, we define a measure of a population's penalty of ignorance based on the Kullback–Leibler index that combines the contributions of resource selection (i.e. biased use of breeding sites) and density‐dependent depletion. Third, we quantify the extent to which environmental heterogeneity (i.e. mean and variance within a landscape) constrains sustainable population growth of unbiased agents. We call this the heterogeneity‐based fitness deficit, and combine this with population simulations to quantify the independent contribution of information‐use strategies to the total population growth rate. We further capitalize on this example to highlight the interactive effects of information between ecological scales when fear affects individual fitness through phenotypic plasticity. Informed breeding habitat selection moderates the demographic cost of fear commensurate with density‐dependent information use. Thus, future work should attempt to differentiate between phenotypic plasticity (i.e. acute fear) and demographic responses (i.e. chronic changes in population size). We conclude with a broader discussion of information in alternative contexts, and explore some evolutionary considerations for information use. We note how competition among individuals may constrain the information state among individuals, and the implications of this constraint under environmental change. This article is protected by copyright. All rights reserved.
  • ... Clutch predation is an important source of reproductive failure in birds ( Ricklefs 1969;Macdonald and Bolton 2008), particularly in the Arctic (e.g., McKinnon et al. 2010). If the risk of clutch predation varies intraseasonally (Smith and Wilson 2010), clutch predation could additionally constrain or favor phenological change of avian reproduction in step with their arthropod prey ( Dunn and Winkler 2010;Schmidt et al. 2015). To date, such topdown selective pressures by organisms at higher trophic levels that feed upon birds and their offspring have yet to be examined as a factor that may limit a forward shift in the timing of breeding ( Both et al. 2009). ...
    ... If the fitness costs of arriving in a period with low food abundance and/or high energetic costs are larger than the costs of chicks hatching out of synchrony with their prey, no strong selection for a phenological match between food abundance and hatch date would be expected. Schmidt et al. (2015) suggested that clutch predation may prevent phenological shifts in response to climate change. More recently, Harts et al. (2016) suggested that a higher predation risk on early arriving individuals may select for later arrival times of migratory birds. ...
    Article
    Full-text available
    Climate change may influence the phenology of organisms unequally across trophic levels and thus lead to phenological mismatches between predators and prey. In cases where prey availability peaks before reproducing predators reach maximal prey demand, any negative fitness consequences would selectively favor resynchronization by earlier starts of the reproductive activities of the predators. At a study site in northeast Greenland, over a period of 17 years, the median emergence of the invertebrate prey of Sanderling Calidris alba advanced with 1.27 days per year. Yet, over the same period Sanderling did not advance hatching date. Thus, Sanderlings increasingly hatched after their prey was maximally abundant. Surprisingly, the phenological mismatches did not affect chick growth, but the interaction of the annual width and height of the peak in food abundance did. Chicks grew especially better in years when the food peak was broad. Sanderling clutches were most likely to be depredated early in the season , which should delay reproduction. We propose that high early clutch pre-dation may favor a later reproductive timing. Additionally, our data suggest that in most years food was still abundant after the median date of emergence, which may explain why Sanderlings did not advance breeding along with the advances in arthropod phenology.
  • ... Clutch predation is an important source of reproductive failure in birds (Ricklefs 1969; Macdonald and Bolton 2008), particularly in the Arctic (e.g., McKinnon et al. 2010). If the risk of clutch predation varies intraseasonally (Smith and Wilson 2010), clutch predation could additionally constrain or favor phenological change of avian reproduction in step with their arthropod prey (Dunn and Winkler 2010; Schmidt et al. 2015 ). To date, such topdown selective pressures by organisms at higher trophic levels that feed upon birds and their offspring have yet to be examined as a factor that may limit a forward shift in the timing of breeding (Both et al. 2009). ...
    ... If the fitness costs of arriving in a period with low food abundance and/or high energetic costs are larger than the costs of chicks hatching out of synchrony with their prey, no strong selection for a phenological match between food abundance and hatch date would be expected. Schmidt et al. (2015) suggested that clutch predation may prevent phenological shifts in response to climate change. More recently, Harts et al. (2016) suggested that a higher predation risk on early arriving individuals may select for later arrival times of migratory birds. ...
    Data
    Full-text available
    Climate change may influence the phenology of organisms unequally across trophic levels and thus lead to phenological mismatches between predators and prey. In cases where prey availability peaks before reproducing predators reach maximal prey demand, any negative fitness consequences would selectively favor resynchronization by earlier starts of the reproductive activities of the predators. At a study site in northeast Greenland, over a period of 17 years, the median emergence of the invertebrate prey of Sanderling Calidris alba advanced with 1.27 days per year. Yet, over the same period Sanderling did not advance hatching date. Thus, Sanderlings increasingly hatched after their prey was maximally abundant. Surprisingly, the phenological mismatches did not affect chick growth, but the interaction of the annual width and height of the peak in food abundance did. Chicks grew especially better in years when the food peak was broad. Sanderling clutches were most likely to be depredated early in the season, which should delay reproduction. We propose that high early clutch predation may favor a later reproductive timing. Additionally, our data suggest that in most years food was still abundant after the median date of emergence, which may explain why Sanderlings did not advance breeding along with the advances in arthropod phenology.
  • ... Although the study of breeding habitat selection and dispersal processes is currently boosted by technological developments ( Ponchon et al., 2013) and advanced theoretical works (e.g. Delgado, Barto n, Bonte, & Travis, 2014;Ponchon, Garnier, Gr emillet, & Boulinier, 2015;Schmidt, Johansson, Kristensen, Massol, & Jonz en, 2015), it is still a challenge to relate prospecting, dispersal decisions and actual movements in the field. Indeed, this requires collecting fine temporal scale movement data in contrasting environmental conditions involving hierarchies of spatial scales. ...
    Article
    Full-text available
    Prospecting for a future breeding site may help individuals decide whether to disperse and where to settle. However, little is known about it because of methodological constraints limiting the acquisition of data at fine spatial and temporal resolutions, especially for individuals that have failed breeding. Using recently developed solar-powered GPS-UHF not requiring the recapture of individuals, we tracked failed breeding black-legged kittiwakes, Rissa tridactyla, nesting in a failed subcolony of a large Norwegian colony from the end of incubation and across the chick-rearing period. As predicted, their movement patterns differed significantly from those of successfully breeding birds tracked simultaneously in a nearby successful subcolony. After 1 week of tracking, all failed breeders rapidly abandoned their nesting cliff and males and females simultaneously increased prospecting visits to other parts of their nesting colony and to neighbouring kittiwake colonies situated 40–50 km away. Conversely, none of the successful breeders prospected over the same period. Our results provide new insights on prospecting movements linked to potential dispersal decisions after breeding failure. They suggest that males and females have similar temporal but different spatial prospecting patterns, possibly due to different costs associated with prospecting and dispersal decisions. They also highlight the need to track more comprehensively the movements linked with breeding habitat selection and dispersal in contrasting environmental conditions to better understand the complex behavioural responses of individuals to breeding failure and their consequences for the spatial dynamics of populations.
  • ... It does not permit, for example, some second temporally varying resource on the breeding grounds upon which newly fledged juveniles may depend. It also excludes multi-species interactions, such as predation, which may have their own phenology [39]. Further, the emphasis on caterpillar phenology in particular (e.g. as applied to the Ficedula spp. ...
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    Full-text available
    In migratory birds, arrival date and hatching date are two key phenological markers that have responded to global warming. A body of knowledge exists relating these traits to evolutionary pressures. In this study, we formalize this knowledge into general mathematical assumptions, and use them in an ecoevolutionary model. In contrast to previous models, this study novelty accounts for both traits-arrival date and hatching date-and the interdependence between them, revealing when one, the other or both will respond to climate. For all models sharing the assumptions, the following phenological responses will occur. First, if the nestling-prey peak is late enough, hatching is synchronous with, and arrival date evolves independently of, prey phenology. Second, when resource availability constrains the length of the pre-laying period, hatching is adaptively asynchronous with prey phenology. Predictions for both traits compare well with empirical observations. In response to advancing prey phenology, arrival date may advance, remain unchanged, or even become delayed; the latter occurring when egg-laying resources are only available relatively late in the season. The model shows that asynchronous hatching and unresponsive arrival date are not sufficient evidence that phenological adaptation is constrained. The work provides a framework for exploring microevolution of interdependent phenological traits. © 2015 The Author(s) Published by the Royal Society. All rights reserved.
  • Article
    The combination of spatial structure and non-linear population dynamics can promote the persistence of coupled populations, even when the average population growth rate of the patches seen in isolation would predict otherwise. This phenomenon has generally been conceptualized and investigated through the movement of individuals among patches that each holds many individuals, as in metapopulation models. However, population persistence can likewise increase as the result of individuals moving among sites (e.g. breeding territories) within in a single patch. Here I examine the latter: individuals making small-scale informed decisions with respect to where to breed can promote population persistence in poor environments. Based on a simple algebraic model, I demonstrate information thresholds, and predict that greater information use is required for population persistence under lower spatial heterogeneity in habitat quality, all else equal. Second, I implement an individual-based model to explore prior experience and prospecting on conspecific success within a more complex, and spatially heterogeneous environment. Uniquely, I jointly examine the effects of simulated habitat loss, spatial heterogeneity prior to habitat, and variation in information gathering on population persistence. I find that habitat loss accelerates population quasi-extinction risk; however, information use reduces extinction probabilities in proportion to the level of information gathering. Per capita reproductive success declines with number of breeding sites, suggesting that information-mediated Allee effects may contribute to extinction risk. In conclusion, my study suggests that populations in a changing world may be increasingly vulnerable to extinction where patch size and spatial heterogeneity constrain the effectiveness of information-use strategies. This article is protected by copyright. All rights reserved.
  • Thesis
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    Ecological systems are all spatially structured to some extent, with fluxes of individuals, matter and energy linking habitat patches and, thus, connecting local and regional dynamics. This synthesis is an attempt at summarizing work I have performed since 2008 on the following topics: (i) The emergence and coexistence of phenotypically distinct types, be they genotypes within a species or species within a community, in particular in models explaining the evolution of dispersal polymorphisms and their consequences for communities; (ii) The complexity and functioning of ecological networks. This more recent part of my work has led me to consider models of interaction networks and models of spatially structured ecological systems on directed networks; (iii) The dynamics of spatially structured ecological systems, in particular the consequences of perturbation dynamics in metacommunities and a re-examination of the stability-complexity issue in metaecosystems; (iv) The geographic distributions of species, notably through the improvement of current methods to estimate consensus and uncertainty among different species distribution models and through theoretical models linking maladaptation and gene flow to species range limits. Current perspectives on these topics include developing spatial evolutionary models interaction network, applying network approaches to the prediction of ecosystem services, and improving the general framework of spatially structured ecological systems, e.g. by taking into account symbiotic interactions and their evolution in spatially heterogeneous settings.
  • Article
    Phenology – the seasonal timing of life history events – is of fundamental importance for many ecological interactions. Direct interactions between organisms such as pollination, competitive contests and predation require overlap in time between interacting life stages. By controlling when dur-ing the year individuals are active and available for others as partners, competitors or food resources, phenology thus sets the stage for whether or not such interactions can take place at all. Phenology can also influence interactions quan-titatively: with larger temporal overlap between two inter-acting species their interaction can be expected to become stronger or more probable. From an ecological point of view, investigating phenology is therefore a key to understanding functional aspects of communities and the inner workings of ecosystems. From an evolutionary point of view, timing of a seasonal event can be considered as a type of heritable trait, similar to other life-history traits. As such, it is subject to natural selection, and ecological interactions are potentially important selective forces influencing its evolution. Regardless of whether the focus is on ecology or evolution, studying phenology is fascinating because it is a very general characteristic of populations – the temporal component of their life history that can easily be observed by professionals as well as amateurs. Because phenological traits are expressed by many different types of species and in many different types of activities, they allow for direct comparisons across taxa and ecosystems. Recent climate change has accentuated the need to better understand the ecological and evolutionary implica-tions of phenology. Significant changes in phenology have been observed in many systems across the world and form one of the most well-documented ecological footprints of global warming (Parmesan 2006). Phenological data continues to accumulate in ongoing, large-scale monitoring programs as well as through discoveries of historical archives and increasingly refined methods to monitor changes (Hudson et al. 2010). Although the general ecological implications of changing phenology remain to a large extent unknown, some studies have indicated effects of phenological change on fitness components or population dynamics. How shall we interpret these patterns – do phenological shifts signify growing mismatches with environmental conditions or are they adaptive responses? What are the ecological conse-quences of phenological change – which species will benefit and which will lose? What are the indirect effects when per-turbations owing to phenological shifts propagate through food webs and communities? With the aim of advancing our knowledge on these topics, we invited ecologists with expertise in phenology or theoretical ecology to contribute to this special issue. In particular we wanted to shed light on the interplay between phenology and ecological interactions from different perspectives, resulting in contributions rep-resenting a diverse range of scientific approaches, from field studies and experiments to theoretical investigations based on network theory, game theory, population dynamics and life history theory. The contributions furthermore include original research as well as reviews and conceptual papers that provide overview and synthesis. The first six papers focus on how phenology influences ecological interactions. Forrest (2015) reviews empirical research on phenological change in plant–pollinator inter-actions. The paper highlights that phenological shifts have been observed in a range of systems, but while fitness effects on plants have been documented, less is known about the consequences for pollinators. Several promising avenues for future observational and experimental research are outlined and the author stresses that we need to evaluate the relative importance of mismatch compared to other effects of climate change. Rafferty et al. (2015) put forward a framework to predict the likelihood of phenological mismatch in mutual-istic interactions in general. They argue that while a relatively large amount of attention has been given to plant–pollinator interactions, the implications of phenological shifts for other
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    A model is suggested for certain types of experiments that involve individuals being selected one-by-one from a population consisting of two or more different classes of individuals. Selection with and without replacement is considered and equations are provided for the estimation of the selectivity of the selection process. The equations are illustrated on data from experiments involving selective predation and food competition.
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    Many migratory birds have changed their timing of arrival at breeding grounds in response to recent climate change. Understanding the adaptive value and the demographic consequences of these shifts are key challenges. To address these questions we extend previous models of phenological adaptation to climate change under territory competition to include feedback from population dynamics, winter survival and habitat productivity. We study effects of improved pre-breeding survival and of earlier food abundance peak. We show that phenological responses depend strongly on equilibrium population density via effects on territory competition. When density is high, improved pre-breeding survival affects selection pressures more than shifts of the resource peak. Under certain conditions, an advanced food peak can even select for later arrival due to competitive release. Improved pre-breeding survival has positive effects on population density that in many cases is stronger than negative effects of an advanced food peak. The fraction of young in the population decreases in all scenarios of change, but food peak shifts only affect population structure marginally unless population density is low. This work thus provides several missing links between phenological adaptation and demographic responses, and augments the toolbox for interpreting ongoing phenological shifts in migratory birds. We illustrate the utility of our model by explaining different patterns in demographic trends and phenological shifts in populations of Pied flycatchers (Ficedula hypoleuca) across Western Europe.
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    1. Territory choice is likely to include sequential sampling at prospective sites, a decision rule for accepting a site, and, when available, use of prior experience. Here I consider the threshold rule (Real 1990) in which individuals choose the first option that exceeds a preset level of quality, and ask how competition for sites limits the choosiness of individuals applying the threshold rule. I then investigate how the addition of site fidelity further influences the evolution of individual choosiness via a threshold rule.2. I develop an individual-based model that uses a genetic algorithm approach to search for the optimal threshold as an evolutionary stable strategy (ESS) and equilibrium population size. Territory quality (i.e., likelihood of reproductive success) is spatially heterogeneous. Individuals either use the acceptance threshold alone or with together with site fidelity. In the latter strategy, successful breeders that survive remain at their former site as incumbents, whereas unsuccessful breeders move to a new site.3. Results indicate greater competition for sites increases the acceptance threshold and reduces choosiness even when individuals have perfect information from sampled sites. Incumbency, via site fidelity at successful territories, leads to the evolution of relatively unselective behaviour, but is influenced by the level of adult survival.4. Competition for sites and site pre-emption, rather than energetic or mortality costs, may drive the evolution of choosiness. The analysis also highlights the importance of considering coexisting strategies used by individuals and not simply the population. For instance, site fidelity, as a co-existing strategy, can result in an ESS acceptance threshold that is no better than random selection, and yet still safeguard populations from extinction.This article is protected by copyright. All rights reserved.
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    Climate change is apparent as an advancement of spring phenology. However, there is no a priori reason to expect that all components of food chains will shift their phenology at the same rate. This differential shift will lead to mistimed reproduction in many species, including seasonally breeding birds. We argue that climate change induced mistiming in avian reproduction occurs because there is a substantial period between the moment of decision making on when to reproduce and the moment at which selection operates on this decision. Climate change is therefore likely to differentially alter the environment of decision-making and the environment of selection. We discuss the potential consequences of such mistiming, and identify a number of ways in which either individual birds or bird populations potentially can adapt to reproductive mistiming.
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    A growing body of evidence indicates that vocalizations of predators and perceived risk of predation can significantly alter avian nesting behavior and reproductive performance. However, it is currently unclear whether birds acoustically discriminate among different types of predators and adjust their short-term behavioral responses accordingly. We investigated this issue via playback experiments in which nests of the Hooded Warbler (Setophaga citrina) were exposed to vocalizations of two nest predators, the Blue Jay (Cyanocitta cristata) and Eastern Chipmunk (Tamias striatus), and a dangerous predator of adults and nestlings, Cooper's Hawk (Accipiter cooperii). We used songs of a common nonpredatory passerine, the Red-eyed Vireo (Vireo olivaceus), as a control. In comparison to responses observed during control trials, adult Hooded Warblers delayed their return to the nest following playback of Cooper's Hawk but returned more quickly after playback of the Eastern Chipmunk, pro­bably because Cooper's Hawks are a threat to adult Hooded Warblers while Eastern Chipmunks pose a risk only to eggs and nestlings. Time of return to the nest following playback of the Blue Jay was nearly identical to that after controls, possibly because of the relative rarity of Blue Jays in our study area. Despite its significant effect on return time, playback had no effect on the number of times adults fed nestlings in the following hour. Overall, our results suggest that nesting Hooded Warblers discriminate among the vocalizations of potential predators and adjust the time of return to their nest according to the nature and degree of perceived risk. Cada vez más evidencia indica que las vocalizaciones de los depredadores y el riesgo de depredación percibido pueden alterar significativamente el comportamiento de nidificación de las aves y el rendimiento reproductivo. Sin embargo, actualmente no está claro si las aves discriminan por medios acústicos los diferentes tipos de depredadores y ajustan en concordancia sus respuestas de comportamiento de corto plazo. Investigamos este asunto por medio de experimentos de reproducción de sonidos previamente grabados en los cuales se expusieron nidos de Setophaga citrina a vocalizaciones de dos depredadores de nido, Cyanocitta cristata y Tamias striatus, y a un depredador peligroso de adultos y pichones, Accipiter cooperii. Empleamos cantos de un paserino común que no es depredador, Vireo olivaceus, como control. En respuesta a esto, luego de la reproducción del sonido control, los adultos de S. citrina demoraron el retorno a sus nidos luego de la reproducción del sonido de A. cooperii pero retornaron más rápido luego de la reproducción del sonido de T. striatus, probablemente debido a que A. cooperii es una amenaza para los adultos de S. citrina mientras que T. striatus representa un riesgo solo para los huevos y los pichones. El tiempo de retorno al nido luego de la reproducción del sonido de C. cristata fue casi idéntico al del control, posiblemente debido a la rareza relativa de C. cristata en nuestra área de estudio. A pesar de su efecto significativo sobre el tiempo de retorno, la reproducción de sonidos previamente grabados no tuvo un efecto sobre el número de visitas para alimentar a los pichones durante la hora siguiente. De forma global, nuestros resultados sugieren que los individuos nidificando de S. citrina discriminan entre las vocalizaciones de los depredadores potenciales y ajustan el tiempo de retorno a sus nidos de acuerdo a la naturaleza y al grado de riesgo percibido.
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    Breeding habitat selection is expected to be adaptive. Animals should respond to strong agents of natural selection, such as expected offspring mortality due to nest predators, in their settlement decisions. In birds, mammalian nest predators are a significant mortality source and birds are known to respond to their presence. However, the mechanism used by birds to perceive mammalian nest predators and estimate the nest predation risk remains unknown, in particular at larger spatial scales while comparing potential breeding habitat patches. We experimentally tested whether the farmland bird community can detect and perceive cues of a mammalian nest predator (urine and feces), and how this perception affected the habitat selection and community structure of birds. The experiment was conducted at a large habitat patch scale by simulating a high abundance of nest predator by spraying on the ground water with dissolved mink excrements, whereas water was sprayed in the control treatment. Birds avoided settling in the plots treated with nest predator excrement. The number of migratory passerine species and their total density were lower in the simulated predation risk treatment than in the control treatment. Our results revealed a novel antipredator behavioral mechanism in birds; passerine birds can detect the excrements of mammalian nest predators and thereby assess the relative nest predation risk among potential breeding habitat patches. This mechanism has direct impacts on the structure of avian breeding bird community.
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    Using constant effort (1993-1996) and playback mist netting with color banding (1996-1999), we estimated annual survival rates of Ovenbirds (Seiurus aurocapillus) and American Redstarts (Setophaga ruticilla) at four sites in the boreal forest of central Saskatchewan. For both species, the model that best described our data included a residency index that differentiated individuals caught more than once within the breeding season of initial capture (residents) from individuals caught only once (transients). Transients had considerably lower recapture rates than residents. The residency index was a more effective means of addressing violations of the homogeneity of capture assumption inherent in Cormack-Jolly-Seber models than a two-stage or age- structured model. We detected no significant differences in survival or recapture rate of male Ovenbirds between constant effort and playback mist netting techniques, although our estimate of annual survival for male Ovenbirds captured using playback (0.62 6 0.06 SE) was higher than when we used constant effort netting (0.44 6 0.13 SE). We observed no significant differences in survival between male (n 5 99) and female (n 5 113) American Redstarts or between second-year (n 5 50) and after-second-year (n 5 49) American Redstart males (overall survival 5 0.55 6 0.09 SE). For Ovenbirds, the model that best fit the data incorporated sex specific differences in survival with females (n 5 76) having lower survival (0.21 6 0.09 SE) than males (n 5 197, 0.60 6 0.12 SE). Without accounting for the presence of transient birds in our models, our estimates of survival would have been unrealistically low. Residency indices based on the number of times an individual was captured within a season seem to provide an effective means to account for transients. Received 27 November 2001, accepted 15 July 2002.
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    First-order difference equations arise in many contexts in the biological, economic and social sciences. Such equations, even though simple and deterministic, can exhibit a surprising array of dynamical behaviour, from stable points, to a bifurcating hiearchy of stable cycles, to apparently random fluctuations. There are consequently many fascinating problems, some concerned with delicate mathematical aspects of the fine structure of the trajectories, and some concerned with the practical implications and applications. This is an interpretive review of them.
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    Broad-scale environmental changes are altering patterns of natural selection in the wild, but few empirical studies have quantified the demographic cost of sustained directional selection in response to these changes. We tested whether population growth in a wild bird is negatively affected by climate change–induced phenological mismatch, using almost four decades of individual-level life-history data from a great tit population. In this population, warmer springs have generated a mismatch between the annual breeding time and the seasonal food peak, intensifying directional selection for earlier laying dates. Interannual variation in population mismatch has not, however, affected population growth. We demonstrated a mechanism contributing to this uncoupling, whereby fitness losses associated with mismatch are counteracted by fitness gains due to relaxed competition. These findings imply that natural populations may be able to tolerate considerable maladaptation driven by shifting climatic conditions without undergoing immediate declines.
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    Species can either adapt to new conditions induced by climate change or shift their range in an attempt to track optimal environmental conditions. During current range shifts, species are simultaneously confronted with a second major anthropogenic disturbance, landscape fragmentation. Using individual-based models with a shifting climate window, we examine the effect of different rates of climate change on the evolution of dispersal distances through changes in the genetically determined dispersal kernel. Our results demonstrate that the rate of climate change is positively correlated to the evolved dispersal distances although too fast climate change causes the population to crash. When faced with realistic rates of climate change, greater dispersal distances evolve than those required for the population to keep track of the climate, thereby maximizing population size. Importantly, the greater dispersal distances that evolve when climate change is more rapid, induce evolutionary rescue by facilitating the population in crossing large gaps in the landscape. This could ensure population persistence in case of range shifting in fragmented landscapes. Furthermore, we highlight problems in using invasion speed as a proxy for potential range shifting abilities under climate change.
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    From 1971 through 2003, Ovenbirds (Seiurus aurocapilla) at the Hemlock Hill Biological Research Area in northwestern Pennsylvania never bred in forest interior. Instead, they exhibited atypical habitat selection for breeding by occupying regenerating forest edges. Pairs in 14 territories, the entire population, showed normal annual return rates and pairing rates compared with other studies. For this ground-foraging bird, other studies showed that deep soil litter is preferred—but at my study site, soil litter depth in Ovenbird-occupied areas was lower than that found in the unoccupied forest interior. During May, July, and August, songs played in forest interior to attract Ovenbirds to settle there were unsuccessful. I tested the hypothesis that eastern chipmunk (Tamias striatus) abundance influenced this atypical habitat selection. Chipmunks were nearly absent from Ovenbird territories, but were abundant in the forest interior. I discuss habitat selection in birds in relation to simple cues and relate this to variation in habitat selection and use found in Ovenbirds.
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    The seasonal timing of avian reproduction is supposed primarily to coincide with favourable feeding conditions. Long-term changes in avian breeding phenology are thus mostly scrutinized in relation to climatic factors and matching of the food supplies, while the role of nesting mortality is largely unexplored. Here we show that higher seasonal mean daily mortality rate leads to a shift in the distribution of breeding times of the successful nests to later dates in an an open-nesting passerine bird, the red-backed shrike Lanius collurio. The effect appeared to be strong enough to enhance or counteract the influence of climatic factors and breeding density on the inter-annual variation in mean hatching dates. Moreover, the seasonal distribution of reproductive output was shifted to larger, or smaller, broods early in the season when the nesting mortality increased, or decreased, respectively, during the season. We suggest that population level changes in timing of breeding caused by a general advancement of spring and of the food supplies might be altered by the seasonality in nesting mortality. Hence, we argue that consideration of nesting mortality is of major importance for understanding long-term trends in avian phenology, particularly in species capable of renesting.
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    Summary • Intraguild predation (IGP) has been studied extensively in predatory fish, amphibians and mammals, but less so in top avian predators. We studied the impact of IGP by large eagle owls Bubo bubo Linnaeus (body mass ∼1·5–4 kg) on diurnal black kites Milvus migrans Boddaert (∼0·5–1 kg) in eight populations located in the Italian Alps. Eagle owls preyed on both adult and nestling kites, especially when kites nested within 2 km of an owl nest. Food overlap was low as kites preyed mainly on fish and owls on mammals. Eagle owls were absent from two study areas, bred very close to another area and were present at medium–high densities in the other five. Within-population effects varied and were most severe in areas with high owl densities. Overall, kites responded to predation risk through predator spatial avoidance, being concentrated in interstitial predation-refugia bordering the core home range of owl pairs. • Kite productivity declined steeply with increasing predation risk; no nestling fledged within 1 km of an owl nest. Brood predation was higher in an area with medium owl density than in an area lacking eagle owls. • The abandonment of kite territories increased near owl nests, but close coexistence was maintained by new kite territories being established occasionally in areas of high predation risk and high food abundance, which probably functioned as ecological traps. Compared to a random nest dispersion, colonial nesting was avoided within 1 km of an owl pair and peaked in conditions of medium predation risk. • At the population level, kite density and productivity were related to a complex interaction of IGP risk and food abundance, and were probably shaped by a mixture of top-down and bottom-up effects. These results may apply to many other vertebrate mesopredators, whose individual decisions and population responses are probably the result of a trade-off between predator avoidance and food acquisition. • At the community level, the density of different diurnal avian predators responded differently to IGP risk, some of them even increasing with this risk. The diversity of the assemblage peaked at medium–high eagle owl density. Future studies of top vertebrate predators need to take more account of IGP effects. Their conservation management needs to be highly case-specific and framed within a broader ecosystem perspective.
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    Global climate change has been shown to cause variable shifts in phenology in a variety of animals and unexpected outcomes across food chains are to be found. Here we examined how rising annual spring temperatures affected the interactions between seed masting, cavity nesting birds and dormice using long-term data from Eastern Czech Republic. We have shown that climate change was associated with unequal shifts in the phenology of two cavity-breeding groups: dormice and birds. Rising spring temperatures have progressively advanced the termination of hibernation for the edible dormouse Glis glis, a common bird predator, leading to an increasing overlap in the use of nesting boxes between dormice and birds. In contrast, only the collared flycatcher Ficedula albicollis, of the four cavity-nesting bird species, advanced its breeding dates in response to rising temperatures. At the same time, favourable weather conditions, coupled with good seed masting years, have been associated with a substantial rise in dormice numbers. Concurrent with the increasing dormice abundance, the number of bird nests destroyed significantly increased in three out of four bird species. We showed that while there was a significant change in the date that the dormice emerged from hibernation during the course of the study, it did not significantly contribute to predation levels when controlling for their abundance and timing of breeding in birds. We found that the increasing dormice abundance was the main factor causing high brood losses in birds, while the timing of breeding in birds had a variable effect between bird species. This study illustrates how changes in climate might affect organisms at various trophic levels with often unexpected outcomes. Limited evidence from other study organisms suggests that species most at risk are those at different trophic levels that do not shift at the same rate or in the same direction as their food resources, predators or competitors.
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  • Continuous-trait game theory fills the niche of enabling analytically solvable models of the evolution of biologically realistically complex traits. Game theory provides a mathematical language for under- standing evolution by natural selection. Continuous-trait game the- ory starts with the notion of an evolutionarily stable strategy (ESS) and adds the concept of convergence stability (that the ESS is an evo- lutionary attractor). With these basic tools in hand, continuous-trait game theory can be easily extended to model evolution under con- ditions of disruptive selection and speciation, nonequilibrium pop- ulation dynamics, stochastic environments, coevolution, and more. Many models applying these tools to evolutionary ecology and co- evolution have been developed in the past two decades. Going for- ward we emphasize the communication of the conceptual simplicity and underlying unity of ideas inherent in continuous-trait game the- ory and the development of new applications to biological questions.
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    During nine years of study, we detected a mechanism corresponding to site dependence operating in a population of the sedge warbler Acrocephalus schoenobaenus inhabiting a natural wetland of high within-habitat heterogeneity. Sites with a larger share of cover by tall wetland vegetation were preempted during spring settlement; they were occupied in more breeding seasons and by more experienced males. The fitness of males occupying these sites was higher in terms of local recruit production. The total area occupied by the population expanded or contracted depending on its population size. This mechanism increased or decreased the mean site quality, influencing local recruitment of young, although mainly by changing the share of unproductive sites in the total pool of occupied sites. The results indicate that population demographic rates may depend on the spatial heterogeneity of resources at the level of individuals.
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    1. It is widely accepted that the arrival order of migratory birds is correlated with the condition of the birds, which leads to high quality individuals occupying prime sites. However, the theoretical backgrounds for this argument have been lacking. A simple game-theoretic model of arrival timing is provided which investigates the evolutionary stability of condition-dependent arrival order in territorial migrant birds. 2. Competition for territories or other priority-dependent benefits can lead to arrival dates far preceding the cost-minimizing date (the optimum date in the absence of competition) for all but the weakest individuals. Increasing the number of competitors can generate a ‘cascading’ competition for early arrival, which advances arrival dates further apart from the individual optimum dates for the onset of breeding. 3. At equilibrium, arrival order corresponds strictly to condition order only if marginal costs of advancing arrival are always larger for individuals in lower condition. If spring mortality vacates territories for later-arriving birds, the criterion for ‘honest’ arrival order becomes still stricter: differential survival costs should exist, but survival differences among individuals (or, alternatively, territory quality differences) should not be very large. 4. If the habitat is saturated so that there is a risk of not obtaining a territory at all, or if worst territories are of much lower value than the rest, competition may lead to the majority of the population arriving within a fairly short interval, followed by a much later floating fraction. This synchrony in the arrival of breeders imposes an increasing cost for the lesser fit breeding birds. Thus, arrival costs paid are not necessarily highest for earliest arriving individuals, but for those who have the most to lose if they drop a few steps in the arrival order. 5. Competition for high quality territories can also lead to partial migration, in which case birds in good condition are expected to be most likely to remain resident.