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.     

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.     

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.     

The use of conspecific reproductive success for breeding patch selection in terrestrial migratory species

Classical models of breeding habitat selection rarely deal with the question of information gathering for patch quality assessment. In this paper, we present two models comparing the fitness outcomes of behavioural strategies based on conspecific reproductive success as a cue to assess local environmental quality before selecting a new breeding habitat. The models deal with two phases of the life-cycle of a territorial migratory species: recruitment to a breeding population (model 1) and breeding site fidelity of subsequent breeding attempts (model 2). The first model shows that prospecting breeding patches before recruiting is the best strategy if the environment is predictable and contains a low proportion of good patches, even if it implies losing a breeding opportunity. The second model shows that dispersing after a breeding attempt according to the patch's breeding success rather than the individual's own success is the bests own success is the best strategy if the environment is patchy. These results underline the importance of studying the spatio-temporal variations of factors affecting reproductive success when considering the importance of habitat selection strategies based on conspecifics. Moreover, they allow the understanding of individual behaviour patterns observed in natural populations and their potential consequences at the metapopulation level.     

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.     

Public information affects breeding dispersal in a colonial bird: kittiwakes cue on neighbours

Habitat selection and dispersal behaviour are key processes in evolutionary ecology. Recent studies have suggested that individuals may use the reproductive performance of conspecifics as a source of public information on breeding patch quality for dispersal decisions, but experimental evidence is still limited for species breeding in aggregates, i.e. colonial species. We addressed this issue by manipulating the local breeding success of marked individuals and that of their neighbours on a series of breeding patches of a colonial seabird, the black-legged kittiwake (Rissa tridactyla). Based on previous observations in this species, we predicted that individuals that lost their eggs on successful patches would attend their nest and come back to it the year after at a higher rate than individuals that lost their eggs on patches where their neighbours were also in failure. As predicted, the attendance of breeders and prospectors was strongly affected by the local level of breeding success, resulting in differential site fidelity and recruitment. This suggests that individuals used information conveyed by conspecific breeding performance to make decisions relative to breeding site selection. This process can amplify the response of these populations to environmental change and may have contributed to the evolution of colonial breeding.     

Can settlement in natal-like habitat explain maladaptive habitat selection?

The study of habitat selection has long been influenced by the ideal free model, which maintains that young adults settle in habitat according to its inherent quality and the density of conspecifics within it. The model has gained support in recent years from the finding that conspecifics produce cues inadvertently that help prebreeders locate good habitat. Yet abundant evidence shows that animals often fail to occupy habitats that ecologists have identified as those of highest quality, leading to the conclusion that young animals settle on breeding spaces by means not widely understood. Here, we report that a phenomenon virtually unknown in nature, natal habitat preference induction (NHPI), is a strong predictor of territory settlement in both male and female common loons (Gavia immer). NHPI causes young animals to settle on natal-like breeding spaces, but not necessarily those that maximize reproductive success. If widespread, NHPI might explain apparently maladaptive habitat settlement.     

Microhabitat preferences of longear sunfish: low light intensity versus submerged cover

Both cover and light intensity are important factors in microhabitat selection of fishes, suggesting a possible hierarchical relationship. Many centrarchids have been shown to prefer low light intensities and heavy submerged cover, but adult nonbreeding longear sunfish are reported to occupy sparsely vegetated, clear, shallow water during the brightest part of the day, probably for foraging. To determine the relative importance of cover and light intensity to longear sunfish, we presented nonbreeding adults with choices between these two conditions in a series of three laboratory experiments. Longear sunfish preferred low light to high light intensity and preferred submerged cover to no cover. However, when given a choice, they preferred to occupy low light intensity conditions without cover rather than submerged cover under higher light intensity conditions. Thus, low light intensity, such as is found in greater pool depths, may be the preferred refuge from predation for longear sunfish.