Competitor phenology as a social cue in breeding site selection

Abstract

Summary 1.Predicting habitat quality is a major challenge for animals selecting a breeding patch, because it affects reproductive success. Breeding site selection may be based on previous experience, or on social information from the density and success of competitors with an earlier phenology. 2. Variation in animal breeding phenology is often correlated with variation in habitat quality. Generally, animals breed earlier in high-quality habitats that allow them to reach a nutritional threshold required for breeding earlier or avoid nest predation. In addition, habitat quality may affect phenological overlap between species and thereby interspecific competition. Therefore, we hypothesized that competitor breeding phenology can be used as social cue by settling migrants to locate high-quality breeding sites. 3. To test this hypothesis, we experimentally advanced and delayed hatching phenology of two resident tit species on the level of study plots and studied male and female settlement patterns of migratory pied flycatchers Ficedula hypoleuca. The manipulations were assigned at random in two consecutive years, and treatments were swapped between years in sites that were used in both years. 4. In both years, males settled in equal numbers across treatments, but later arriving females avoided pairing with males in delayed phenology plots. Moreover, male pairing probability declined strongly with arrival date on the breeding grounds. 5. Our results demonstrate that competitor phenology may be used to assess habitat quality by settling migrants, but we cannot pinpoint the exact mechanism (e.g. resource quality, predation pressure or competition) that has given rise to this pattern. 6. In addition, we show that opposing selection pressures for arrival timing may give rise to different social information availabilities between sexes. We discuss our findings in the context of climate warming, social information use and the evolution of protandry in migratory animals.

Heterospecific Nest Site Copying Behavior in a Wild Bird: Assessing the Influence of Genetics and Past Experience on a Joint Breeding Phenotype

“…The low female contribution to the joint phenotype observed here contrasts with another recent experimental study in the pied flycatcher, where only females used tit phenology as a source of social information for breeding site selection (Samplonius and Both, 2017). Even though our study is not directly comparable with that of Samplonius and Both (2017), both report differences between sexes in social information use for breeding site selection, and our results also suggest a differential effect of individual experience as reflected by age and dispersal status between sexes. Such between-sex differences may result from sex-specific information gathering processes (Reed et al, 1999;Doligez et al, 2004b), in relation to sex-specific fitness benefits associated with breeding system and dispersal processes (Greenwood, 1980).…”

“…These sex-specific selective pressures acting on the knowledge of the environment and information gathering may translate into the use of different information sources (including social information) between sexes and/or differential use of the same information depending on individual experience, as suggested here. Both our results and previous results (Samplonius and Both, 2017) are coherent with a preponderant use of fine-scale social information by males and large-scale social information by females. Estimates for the selected fixed and random effects are presented for the male and female full models, and for the selected model for females.…”

“…When tit reproduction is delayed, the number of tit demonstrators upon flycatcher arrival from wintering grounds, and thus the strength and possibly the reliability of heterospecific information, may decrease, due in particular to environmental stochasticity (see also Parejo, 2016 for a discussion on information mismatching). Interestingly, female pied flycatchers have been shown to prefer settling in forest patches where tit phenology is early (Samplonius and Both, 2017). Here, we found no effect of the date of choice by flycatchers or the proportion of nest boxes occupied by tit pairs in the patch, which suggests that the number of tit demonstrators may FIGURE 3 | Female probability to copy in subsequent nest site choices, given previous copying behavior and the difference in exposure to the apparent tit preference compared to the previous year.…”

Interspecific aggression declines seasonally in breeding great tits Parus major

“…It is generally shown that resident species are more plastic in their response to temperature than migrants (Phillimore et al, ; Samplonius et al, ), causing their breeding phenologies to diverge. Such differential divergence has been shown to affect information use (Samplonius & Both, ), and here I show it could affect competitive interactions. This could mean that arriving competitors will encounter fewer aggressive great tits as climate change continues, because great tits advance their breeding phenology more than later breeding migrants in response to temperature (Samplonius et al, ).…”

Phenological sensitivity to climate change is higher in resident than in migrant bird populations among European cavity breeders

“…Responses in laying or hatching date are often interpreted in relation to the phenology of underlying trophic levels, but it is important to consider that also changes in interspecific competitor timing (Samplonius & Both, ) could act as selection pressures that determine the optimal timing response. European tits and flycatchers are ideal model species to study differential adjustment to climate change.…”