No evidence that nest site choice in Pied Flycatchers is mediated by assessing the clutch size of a heterospecific, the Great Tit

Tore Slagsvold,Karen L Wiebe

doi:10.1007/s10336-021-01900-1

Tore Slagsvold, Karen L Wiebe

Open Access

https://doi.org/10.1007/s10336-021-01900-1

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Abstract

Among species that use similar resources, an individual may benefit by observing and copying the behavioural decision of a heterospecific. We tested the hypothesis of heterospecific social learning in passerine birds, namely that a migrant species, the Pied Flycatcher Ficedula hypoleuca, uses external markings on the nest cavities of a resident species, the Great Tit Parus major, as cues when choosing a nest site. Others have suggested that prospecting flycatchers assess the clutch size of tit “demonstrators” by entering their nest boxes and, assuming that a large clutch indicates a high-quality individual, will copy the nest appearance of tits with large, but not small clutches. During a 4-year period in Norway, we designed a similar study but did not find that flycatchers based their nest choice on the clutch size of tits. Neither were there any relationships between clutch size of the tit and its laying date, incubation behaviour, or the number of eggs visible through nest material during egg-laying so Pied Flycatchers did not use these indirect cues to assess quality of the tutor. Filming of tit nests showed that prospecting flycatchers did not enter tit nest boxes to assess the content. Indeed, incubating female tits only left their nest boxes for short bouts of unpredictable duration so there was little opportunity for flycatchers to inspect the nest contents unnoticed. Our study calls into question the mechanism of using the content of tit nests as public information for choosing traits of nest sites based on external characteristics. We suggest that similar studies of nest site choice in relation to possible social information transfer be replicated more widely.

Highlights

Animals that use information from other species when making their own breeding decisions face the challenge of trying to assess or predict behaviour, of a species that is quite different from themselves but which uses a resource in a way that is worth copying
Because we found no relationship between these indirect cues and clutch size, we tested whether final tit clutch size itself can be assessed by prospecting Pied Flycatchers during the egg-laying period when clutch size is incomplete and when the tits spend much time outside the nest cavity and when flycatchers have been observed to inspect their nest (Forsman et al 2018)
Clutch size and the symbol painted on the focal tit nest box at trial sites where a Pied Flycatcher eventually nested in a 25 m box versus for the nearest Great Tit neighbour

Summary

Introduction

Animals that use information from other species when making their own breeding decisions face the challenge of trying to assess or predict behaviour, of a species that is quite different from themselves but which uses a resource in a way that is worth copying. Some studies of passerine birds provide strong support for information transfer among animal species in the wild (e.g., Avarguès-Weber et al 2013; Slagsvold et al 2013; Farine et al 2015). This includes a series of experiments showing that migratory species, which often face strong time constraints on breeding, use cues from resident species when deciding where to settle (Forsman et al 2002, 2008; Thomson et al 2003). Especially late-arriving migrants, may use cues from resident birds when choosing traits of a nest site (Seppänen et al 2005; Kivelä et al 2014; Morinay et al 2020a)

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