Who is in the neighborhood? Conspecific and heterospecific responses to perceived density for breeding habitat selection

Theoretical models of habitat selection often incorporate negative density dependence. Despite strong negative density‐dependent effects on habitat selection, more recent studies indicate that animals settle near members of their own (conspecific) and other species (heterospecific) when selecting habitat with social cues. Social cue use for habitat selection is particularly common among songbirds, but few studies have investigated if songbirds use social cues to assess conspecific or heterospecific density (as opposed to just presence/absence) when making settlement decisions. We conducted a playback experiment to evaluate if yellow warblers (Setophaga petechia) and willow flycatchers (Empidonax traillii), two potential competitors for breeding habitat, use social cues to assess density (conspecific for warblers and heterospecific for flycatchers) when selecting breeding locations at two spatial scales. We simulated yellow warbler density to be high or low at multiple treatment plots (3.14 ha) with song playback and then evaluated settlement decisions by comparing yellow warbler and willow flycatcher abundances across plots (broad‐scale habitat selection) and individual space use within plots (fine‐scale territory establishment). Yellow warbler density treatments did not affect habitat selection by yellow warblers at the broad scale, but caused individuals to cluster territories at high‐density treatments. Willow flycatchers were most abundant at high‐density treatment plots, but yellow warbler density treatments did not affect territory locations. The results indicate that perceived density affects the habitat selection process for both conspecifics and heterospecifics.     

Space use and social association in a gregarious ungulate: Testing the conspecific attraction and resource dispersion hypotheses

Animals use a variety of proximate cues to assess habitat quality when resources vary spatiotemporally. Two nonmutually exclusive strategies to assess habitat quality involve either direct assessment of landscape features or observation of social cues from conspecifics as a form of information transfer about forage resources. The conspecific attraction hypothesis proposes that individual space use is dependent on the distribution of conspecifics rather than the location of resource patches, whereas the resource dispersion hypothesis proposes that individual space use and social association are driven by the abundance and distribution of resources. We tested the conspecific attraction and the resource dispersion hypotheses as two nonmutually exclusive hypotheses explaining social association and of adult female caribou (Rangifer tarandus). We used location data from GPS collars to estimate interannual site fidelity and networks representing home range overlap and social associations among individual caribou. We found that home range overlap and social associations were correlated with resource distribution in summer and conspecific attraction in winter. In summer, when resources were distributed relatively homogeneously, interannual site fidelity was high and home range overlap and social associations were low. Conversely, in winter when resources were distributed relatively heterogeneously, interannual site fidelity was low and home range overlap and social associations were high. As access to resources changes across seasons, caribou appear to alter social behavior and space use. In summer, caribou may use cues associated with the distribution of forage, and in winter caribou may use cues from conspecifics to access forage. Our results have broad implications for our understanding of caribou socioecology, suggesting that caribou use season‐specific strategies to locate forage. Caribou populations continue to decline globally, and our finding that conspecific attraction is likely related to access to forage suggests that further fragmentation of caribou habitat could limit social association among caribou, particularly in winter when access to resources may be limited.     

Species interactions and population density mediate the use of social cues for habitat selection

1. The perspective that populations and communities are structured by antagonistic interactions among individuals has dominated much of ecology. Yet how animals use social information to guide decisions, such as habitat selection, may be influenced by both positive and negative interactions among individuals. Recent theory also suggests that the way animals use social information may be substantially influenced by population density, which alters the potential costs and benefits of such behaviours. 2. I manipulated cues of two competitors, the dominant least flycatcher Empidonax minimus (Baird & Baird) and the subordinate American redstart Setophaga ruticilla (Linnaeus), to assess the use of conspecific and heterospecific cues during habitat selection, and if population density influences these strategies. The experiment consisted of surveying birds during a pre-treatment year, which allows for the control and testing the effect of baseline densities, and a treatment year, in which treatments were applied just prior to settlement. Treatments included broadcasting songs of flycatchers and redstarts, and were compared with controls. 3. When controlling for pre-treatment densities, bird densities, and to a lesser extent arrival dates, during the treatment year suggested that flycatchers were attracted to both conspecific and heterospecific cues during settlement. Furthermore, attraction was strongest for flycatchers in plots with moderate pre-treatment densities. American redstarts were rare in the study area but showed apparent attraction to conspecifics and avoidance of heterospecifics. 4. These results provide experimental evidence for the use of multiple social cues in habitat selection and suggest that heterospecific attraction may operate under broader contexts than originally envisioned. In such instances, nontarget effects can potentially occur when manipulating social cues to elicit settlement in conservation strategies. The impact of population density on the use of social cues shown here can also influence our understanding of metapopulation dynamics by causing complex threshold effects on the likelihood of rescue, which may influence metapopulation stability and the likelihood of local extinction.     

Conspecific attraction in a grassland bird, the Baird's Sparrow

ABSTRACT.   Territorial songbirds generally use song to defend territories and attract mates, but conspecific song may also serve as a cue to attract other male songbirds to a breeding site. Although known to occur in some colonial and forest-associated species, only recently have investigators examined conspecific attraction in grassland species. We used a playback experiment to examine the possible role of conspecific attraction for males searching for potentially suitable breeding habitat in a grassland specialist, the Baird's Sparrow ( Ammodramus bairdii ). Experimental playback plots and control plots with similar landscape and vegetation characteristics were established at two sites in North Dakota. Baird's Sparrows colonized three of six experimental plots and none of six control plots. Males on experimental plots established territories adjacent to the playback stations and were sometimes observed counter-singing with the playback of conspecific songs. Vegetation characteristics were similar on all study plots, and did not explain differences in bird density on our treatment plots. Although we found that playback of conspecific songs attracted male Baird's Sparrows to previously unoccupied, potentially suitable habitat, further experiments are needed to examine the importance of conspecific attraction relative to other cues that birds may use, such as vegetation features. The conservation and management implications of conspecific attraction are not completely understood, but the presence of conspecifics should be considered as a potential cue in habitat selection by all species of birds.     

Testing the conspecific attraction hypothesis with Dupont's Larks,a resident species of songbird in central Spain

Some birds use social cues, such as the presence of conspecifics, when selecting breeding habitat. This phenomenon, known as conspecific attraction, has been well‐documented in migratory species, but has not been assessed for resident species of birds. We used Dupont's Larks (Chersophilus duponti) as a model species to determine if conspecific attraction plays a role in habitat selection by resident species of birds. At our study site in Soria province in central Spain, we monitored two potential habitat patches and one managed site where management actions had provided apparently suitable habitat. At each site, we broadcast recordings of the songs and calls of male Dupont's Larks, and monitored their presence during the breeding season and dispersal period in 2018 using automated recorders and field surveys. No birds were attracted to our study sites. Our results suggest that management of patches of suitable habitat should occur close to areas (within 1 km) already occupied by Dupont's Larks to encourage natural colonization because, based on our results, playback of conspecific vocalizations may not attract the species to new breeding areas. However, additional studies are needed before drawing conclusions about the effectiveness of conspecific attraction for this and other resident species of birds.     

Managing breeding forest songbirds with conspecific song playbacks

Recent studies confirm that several territorial songbird species use conspecific cues, including song, when selecting habitat. We conducted a controlled experiment with a population of black-throated blue warblers Dendroica caerulescens , a species of concern in boreal hardwood transition forests, to determine whether song playbacks influence settlement patterns. We tested whether conspecific song broadcast during spring arrival attracts black-throated blue warblers during territory establishment, and whether song playbacks shift territories from the previous year's breeding distributions. The results of our experiment demonstrate that song playbacks significantly increased territorial occupancy and shifted territories closer to the speakers. Loss of breeding habitat is implicated in population declines of many songbirds, and our results suggest that song playbacks should be further investigated as a tool for mitigating the effects of disruptive management actions. Additional work should consider the spatial arrangement of playback speakers to avoid attracting birds from safe areas. The demographic consequences of conspecific attraction must also be explored before this technique is widely implemented.     

Conspecific Attraction is a Missing Component in Wildlife Habitat Modeling

Abstract Wildlife biologists use knowledge about wildlife-habitat relationships to create habitat models to predict species occurrence across a landscape. Researchers attribute limitations in predictive ability of a habitat model to data deficiencies, missing parameters, error introduced by specifications of the statistical model, and natural variation. Few wildlife biologists, however, have incorporated intra- and interspecific interactions (e.g., conspecific attraction, competition, predator-prey relationships) to increase predictive accuracy of habitat models. Based on our literature review and preliminary data analysis, conspecific attraction can be a primary factor influencing habitat selection in wildlife. Conspecific attraction can lead to clustered distributions of wildlife within available habitat, reducing the predictive ability of habitat models based on vegetative and geographic parameters alone. We suggest wildlife biologists consider incorporating a parameter in habitat models for the clustered distribution of individuals within available habitat and investigate the mechanisms leading to clustered distributions of species, especially conspecific attraction.     

Wood warblers copy settlement decisions of poor quality conspecifics: support for the tradeoff between the benefit of social information use and competition avoidance

Social information use in songbird habitat selection commonly involves a conspecific attraction strategy. Individuals copy the breeding‐site choices of conspecifics, that is, bias their own settlement decisions towards sites (tracts of spatially limited habitat with similar structure) already occupied by others. In order to be adaptive, social information use has to be discriminative. Especially the decisions of good quality individuals, i.e. measuring high at observable fitness correlates, should be copied more frequently than those of poor quality individuals. It is unknown, however, whether songbirds discriminatively use conspecific presence by evaluating the quality of information providers in habitat selection. We experimentally tested whether wood warblers Phylloscopus sibilatrix selectively copied settlement decisions of conspecifics in relation to the quality of observed individuals. We also tested whether the use of social cues was influenced by the population density at a particular site in the preceding year. We found that wood warblers selectively used intraspecific social information, but in a pattern opposite to that expected based on existing hypotheses. Wood warblers copied breeding‐site choices of poor quality conspecifics and despite temporary attraction to sites where the presence of good quality individuals was simulated, they did not ultimately settle near these individuals. Population density in the preceding year did not influence settlement patterns. We argue that when making settlement decisions, wood warblers assessed the expected level of local intraspecific competition and selectively copied breeding‐site choices of conspecifics or refused to settle, depending on competitive abilities of observed individuals. This adds a novel aspect to the patterns and processes of social information use proposed thus far, and provides support for the predicted negative effect of intraspecific competition on benefit of information. Moreover, it seems that habitat selection in wood warblers is a complex decision‐making process, in which initial decisions are adjusted after acquiring more accurate information. Synthesis Social information use in songbird habitat selection commonly involves copying the breeding‐site choices of conspecifics (so‐called conspecific attraction). To be adaptive, this strategy has to be discriminative, but almost no empirical studies have tested this assertion. Our study shows that birds may selectively use social information by copying settlement decisions of poor quality conspecifics, but avoid settling near good quality individuals, likely because of their high competitive abilities. This decision‐making pattern supports the predicted, yet not experimentally tested, tradeoff between information value and cost of competition in social information use. Our study highlights also that the use of social cues in settlement decisions may be both positively and negatively biased.     

Effect of conspecific attraction on the presence of Northern Bobwhites

Researchers and managers have used the tendency of some species of birds to settle near conspecifics (i.e., conspecific attraction) to help establish or reestablish species of conservation concern in targeted habitats. However, most studies of conspecific attraction as a recruitment tool have been conducted with either migratory or colonial-breeding species, and less is known about the possible importance of conspecific attraction for resident species. In 2017 and 2018 in Louisiana, we examined the possible use of conspecific attraction as a management tool for Northern Bobwhites (Colinus virginianus), game birds that are year-round residents. We used an alternating split experimental design across years where Northern Bobwhite vocalizations were broadcast at half of our study sites during the first year of our study and the other half were controls. The following year, experimental sites became controls, and controls became experimental sites. We also assessed land cover at each site to determine if variation in habitat composition at small spatial scales influenced bobwhite presence. We detected six times more Northern Bobwhites at treatment sites (sites with playback) than control sites and found a positive association between the proportion of grass cover and bobwhite presence. These results suggest that a non-migratory, resident species may select breeding locations based, at least in part, on the presence of conspecifics, and that playback of their calls could be incorporated into management plans. Playing back conspecific calls in early spring when Northern Bobwhites are likely searching for breeding locations may facilitate colonization and allow individuals to find locations where managers are attempting to restore their populations.     

Finding a place to live: conspecific attraction affects habitat selection in juvenile green and golden bell frogs

Conspecific attraction plays an important role in habitat selection of several taxa and can affect and determine distribution patterns of populations. The behaviour is largely studied and widespread among birds, but in amphibians, its occurrence seems limited to breeding habitats of adults and gregarious tadpoles. The Australian green and golden bell frogs (Litoria aurea) have suffered considerable shrinking of their original distribution in south-eastern Australia since the 1970s. Currently, with only about 40 populations remaining, the species is considered nationally threatened. In natural conditions, these frogs are aggregated in the landscape and do not seem to occupy all suitable ponds within the occurrence area. To date, studies focusing on the frogs’ habitat have failed in finding a general habitat feature that explains current or past occupancy. This led us to the hypothesis that social cues may play a key role in habitat selection in this species. Using two choice experiments, we tested the preference of juvenile green and golden bell frogs for habitats containing cues of conspecifics of similar size versus habitats without conspecific cues. Tested frogs did not show a preference for habitats containing only scent from conspecifics but did prefer habitats where conspecifics were present. Our results show that conspecific attraction is a determining factor in juvenile green and golden bell frog habitat selection. To our knowledge, this is the first time the behaviour is shown to occur in juvenile frogs in the habitat selection context. From a conservation management point of view, the behaviour may help to explain the failure of reintroductions to areas where the frogs have been extinct, and the non-occupation of suitable created habitats in areas where they still inhabit and develop appropriated management strategies.     

Alternative models of conspecific attraction in flies and crabs

Animals are often attracted to one another when selecting habitats,but little is known about the rules governing conspecific attraction.We use Akaike Information Criterion to evaluate alternativemodels of the effects of conspecifics on individual choice inthe context of habitat selection. One set of models was testedusing data collected on virgin female flies, Drosophila melanogaster,selecting habitats in the laboratory; a second set of modelswas tested using data collected on crabs, Ocypode rotundata,selecting foraging patches in the field. Patterns of space usein the flies were most consistent with models indicating thatindividuals were attracted to other females that selected trapsduring the same hour, as well as to cues left by females thathad entered traps during the previous hour. Results for thecrabs were most consistent with a model which assumes that individualspreferred to join the patch with the most crabs but that theirability to assess the number of crabs in alternative patcheswas constrained by basic psychophysical principles (Weber'slaw). These results provide support for hypotheses about thefunctional significance of conspecific attraction in the fliesand the crabs and illustrate the richness of information aboutconspecific attraction that can be obtained when the same dataset is confronted with alternative models of the ways that animalsrespond to one another when selecting habitats.     

Conspecific attraction and shelter selection in gregarious insects

During habitat selection, the presence of conspecifics can frequently drive a nonuniform distribution of animals across habitats of equivalent quality. In group-living species, subgroups of individuals might display mutual attraction while differing in their preferences for environmental resources. The final decision to settle requires individuals to integrate both environmental and social cues. This raises the question of the relative importance of sociality and resources preferences in determining habitat choice. In this study, we examined the interactive influence of conspecific attraction on individual resource preferences on refuge choice in groups of cockroaches. Shelters scaled to the sizes of nymphs and adult males were offered to groups of only nymphs and only males and to mixed groups. The choices of males were consistent across social conditions. Conversely, the preferences of nymphs shifted depending on the social context; the presence of males overrode the affinity nymphs had for scaled-size shelters. We developed a numerical model implementing parameters derived from these experiments to test whether the final spatial distribution of individuals originated from a differential attraction between nymphs and males that was associated with their relative body size. Finally, we propose a general framework for understanding how similar mechanisms can promote the skewed distribution of organisms at different spatial scales.     

Does attraction to conspecifics explain the patch‐size effect? An experimental test

Recent theory suggests that attraction to conspecifics during habitat selection can be one potential, yet untested, mechanism for animal sensitivity to habitat fragmentation. The least flycatcher Empidonax minimus , a highly territorial migratory bird, has previously been shown to be attracted to conspecifics and sensitive to patch size by avoiding small patches of riparian forest in Montana, USA. I used a large-scale field experiment in this region to test the conspecific attraction hypothesis for explaining sensitivity to patch size, and I supplemented this experiment by estimating whether vegetation structure, nest predation, or nest parasitism rates could better explain patterns of sensitivity to patch size. Vegetation structure did not vary consistently with patch size, based on a random sample of patches across 150  km of the Madison and Missouri Rivers, Montana. Nest predation and parasitism rates by brown-headed cowbirds Molothrus ater also did not vary with patch size during the experiment. However, when conspecific cues were simulated across a gradient of patch sizes, flycatchers settled in all patches – and their sensitivity to patch size vanished – providing strong support for the conspecific attraction hypothesis. These results provide the first experimental evidence that attraction to conspecifics can indeed help explain area sensitivity in nature and highlight how understanding the role of animal behavior in heterogeneous landscapes can aid in interpreting pressing conservation issues.     

Conspecific cues and breeding habitat selection in an endangered woodland warbler

1.?Research on habitat selection has focused on the role of vegetative and geologic characteristics or antagonistic behavioural interactions. 2.?Conspecifics can confer information about habitat quality and provide positive density-dependent effects, suggesting habitat selection in response to the presence of conspecifics can be an adaptive strategy. 3.?We conducted a manipulative field experiment investigating use of conspecific location cues for habitat selection and consequent reproductive outcomes for the endangered golden-cheeked warbler (Setophaga chrysoparia). We investigated the response in woodlands across a range of habitat canopy cover conditions typically considered suitable to unsuitable and using vocal cues presented during two time periods: pre-settlement and post-breeding. 4.?Warblers showed a strong response to both pre-settlement and post-breeding conspecific cues. Territory density was greater than four times higher in treatment sample units than controls. The magnitude of response was higher for cues presented during the pre-settlement period. Positive response to conspecific cues was consistent even in previously unoccupied areas with low canopy cover typically considered unsuitable, resulting in aggregations of warblers in areas generally not considered potential habitat. 5.?Pairing and reproductive success of males was not correlated with canopy cover, as commonly thought. Pairing success and fledging success increased with increasing territory density suggesting that conspecific density may be more important for habitat selection decisions than the canopy cover conditions typically thought to be most important. These results suggest the range of habitat within which birds can perform successfully may be greater than is typically observed. 6.?Our results suggest the territory selection process may not be substantially influenced by competition in some systems. Settlement in response to conspecific cues produced aggregations within larger areas of similar vegetative characteristics. Understanding what cues drive habitat selection decisions and whether these cues are correlated with habitat quality is critical for conserving fitness-enhancing habitats, avoiding creation of ecological traps, generating accurate predictions of species distributions and understanding how occupancy relates to habitat suitability.     

Predation-Related Costs and Benefits of Conspecific Attraction in Songbirds—An Agent-Based Approach

Songbirds that follow a conspecific attraction strategy in the habitat selection process prefer to settle in habitat patches already occupied by other individuals. This largely affects the patterns of their spatio-temporal distribution and leads to clustered breeding. Although making informed settlement decisions is expected to be beneficial for individuals, such territory clusters may potentially provide additional fitness benefits (e.g., through the dilution effect) or costs (e.g., possibly facilitating nest localization if predators respond functionally to prey distribution). Thus, we hypothesized that the fitness consequences of following a conspecific attraction strategy may largely depend on the composition of the predator community. We developed an agent-based model in which we simulated the settling behavior of birds that use a conspecific attraction strategy and breed in a multi-predator landscape with predators that exhibited different foraging strategies. Moreover, we investigated whether Bayesian updating of prior settlement decisions according to the perceived predation risk may improve the fitness of birds that rely on conspecific cues. Our results provide evidence that the fitness consequences of conspecific attraction are predation-related. We found that in landscapes dominated by predators able to respond functionally to prey distribution, clustered breeding led to fitness costs. However, this cost could be reduced if birds performed Bayesian updating of prior settlement decisions and perceived nesting with too many neighbors as a threat. Our results did not support the hypothesis that in landscapes dominated by incidental predators, clustered breeding as a byproduct of conspecific attraction provides fitness benefits through the dilution effect. We suggest that this may be due to the spatial scale of songbirds’ aggregative behavior. In general, we provide evidence that when considering the fitness consequences of conspecific attraction for songbirds, one should expect a trade-off between the benefits of making informed decisions and the costs of clustering.     

Linking Dynamic Habitat Selection with Wading Bird Foraging Distributions across Resource Gradients

Species distribution models (SDM) link species occurrence with a suite of environmental predictors and provide an estimate of habitat quality when the variable set captures the biological requirements of the species. SDMs are inherently more complex when they include components of a species’ ecology such as conspecific attraction and behavioral flexibility to exploit resources that vary across time and space. Wading birds are highly mobile, demonstrate flexible habitat selection, and respond quickly to changes in habitat quality; thus serving as important indicator species for wetland systems. We developed a spatio-temporal, multi-SDM framework using Great Egret (Ardea alba), White Ibis (Eudocimus albus), and Wood Stork (Mycteria Americana) distributions over a decadal gradient of environmental conditions to predict species-specific abundance across space and locations used on the landscape over time. In models of temporal dynamics, species demonstrated conditional preferences for resources based on resource levels linked to differing temporal scales. Wading bird abundance was highest when prey production from optimal periods of inundation was concentrated in shallow depths. Similar responses were observed in models predicting locations used over time, accounting for spatial autocorrelation. Species clustered in response to differing habitat conditions, indicating that social attraction can co-vary with foraging strategy, water-level changes, and habitat quality. This modeling framework can be applied to evaluate the multi-annual resource pulses occurring in real-time, climate change scenarios, or restorative hydrological regimes by tracking changing seasonal and annual distribution and abundance of high quality foraging patches.     

Testing the heterospecific attraction hypothesis with time-series data on species co-occurrence

The distributional patterns of actively moving animals are influenced by the cues that the individuals use for choosing sites into which they settle. Individuals may gather information about habitat quality using two types of strategies, either directly assessing the relevant environmental factors, or using the presence of conspecifics or heterospecifics as an indirect measure of habitat quality. We examined patterns of heterospecific attraction with observational time-series data on a community of seven waterbird species breeding in artificial irrigation ponds. We fitted to the data a multivariate logistic regression model, which attributes the presence–absence of each species to a set of environmental and spatial covariates, to the presence of con- and heterospecifics in the previous year and to the presence of heterospecifics in the same year. All species showed a clear tendency to continue breeding in the same sites where they were observed in the previous year. Additionally, the presence of heterospecifics, both in the previous year and in the same year, generally increased the probability that the focal species was found breeding on a given pond. Our data thus give support for the heterospecific attraction hypothesis, though causal inference should be confirmed with manipulative experiments.     

Disentangling drivers of spatial autocorrelation in species distribution models

Species distribution models (SDMs) are frequently used to understand the influence of site properties on species occurrence. For robust model inference, SDMs need to account for the spatial autocorrelation of virtually all species occurrence data. Current methods do not routinely distinguish between extrinsic and intrinsic drivers of spatial autocorrelation, although these may have different implications for conservation. Here, we present and test a method that disentangles extrinsic and intrinsic drivers of spatial autocorrelation using repeated observations of a species. We focus on unknown habitat characteristics and conspecific interactions as extrinsic and intrinsic drivers, respectively. We model the former with spatially correlated random effects and the latter with an autocovariate, such that the spatially correlated random effects are constant across the repeated observations whereas the autocovariate may change. We tested the performance of our model on virtual species data and applied it to observations of the corncrake Crex crex in the Netherlands. Applying our model to virtual species data revealed that it was well able to distinguish between the two different drivers of spatial autocorrelation, outperforming models with no or a single component for spatial autocorrelation. This finding was independent of the direction of the conspecific interactions (i.e. conspecific attraction versus competitive exclusion). The simulations confirmed that the ability of our model to disentangle both drivers of autocorrelation depends on repeated observations. In the case study, we discovered that the corncrake has a stronger response to habitat characteristics compared to a model that did not include spatially correlated random effects, whereas conspecific interactions appeared to be less important. This implies that future conservation efforts should primarily focus on maximizing habitat availability. Our study shows how to systematically disentangle extrinsic and intrinsic drivers of spatial autocorrelation. The method we propose can help to correctly identify the main drivers of species distributions.     

The heterospecific habitat copying hypothesis: can competitors indicate habitat quality?

According to the "habitat copying" hypothesis, animals use thereproductive performance of conspecifics to assess habitat suitabilityand choose their future breeding site. This is because conspecificsshare ecological needs and thus indicate habitat suitability.Here, we propose the "heterospecific habitat copying" hypothesis,which states that animals should use public information (i.e.,information derived from the performance of others) from con-and heterospecifics sharing ecological needs. In a correlationalapproach we test some assumptions and predictions of this hypothesiswith a data set from two sympatric bird populations, rollers(Coracias garrulus) and kestrels (Falco tinnunculus), usingthe same nest-boxes and exploiting similar food resources. Sincekestrels are residents and breed earlier, we assumed that theyare dominant over rollers for nest-box acquisition. The environmentappears to be patchy for both species and temporally predictablefor kestrels only. Two results suggest that the use of heterospecificpublic information in breeding habitat selection may be at work:(1) an increase in the reoccupancy probability by kestrels ofprevious roller nests with increasing nest success, and (2)an increase in roller breeding population with increasing localkestrel success. Most of the other observed patterns could beexplained by alternative mechanisms such as natal philopatry,breeding fidelity, conspecific attraction, intraspecific habitatcopying, and the effect of interspecific competition.     

Frog breeding pond selection in response to predators and conspecific cues

Predators are a major influence on the breeding site selection decisions of anurans. Many species actively avoid breeding in habitat with predators when given the choice between predator and predator‐free sites. However, certain factors such as site fidelity or conflicting cues may preclude avoidance behavior. We conducted two experiments examining how western chorus frogs, Pseudacris triseriata, respond to predators, western mosquitofish, Gambusia affinis, using an array of artificial ponds located at two field sites. In one experiment, we added G. affinis to half of our experimental ponds and monitored subsequent colonization by frogs. We found that frogs laid significantly fewer eggs in ponds with fish compared to fishless ponds. In another experiment, we introduced an additional cue to complicate the decision‐making process and monitored colonization of ponds in response to treatments of conspecific breeding cues only (eggs), predators (G. affinis) only, and conspecific cues and predators. We found no significant differences in number of eggs deposited among these three treatments. Based on these results, P. triseriata does not always exhibit complete avoidance of fish predators, and avoidance may vary based on factors such as site fidelity or dispersal costs. This study represents a step toward understanding how multiple biotic factors at a breeding pond may influence anuran site selection behavior in the field.