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

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.

Birds do not use social learning of landmarks to locate favorable nest sites

“…Loukola et al (2013) reported that in Finland and Latvia, pied ycatchers chose the nest box that matched the tit's box only when the tit demonstrator had a large clutch size but not when tit clutch size was small. However, there are several logistical and theoretical problems with the SIIU (Slagsvold and Wiebe 2017, 2018) and the results were not replicated in a similar study in Norway (Slagsvold and Wiebe 2021a). The discrepancy among studies is hard to explain but one possibility is that we used a shorter distance between the trial sites on the Norwegian study area (on average 256 m) compared to Finland and Latvia (minimum 1 km; Seppänen et al 2011).…”

Bird nest building: visions for the future

“…[ 59 , 60 ]), appears to be a nest-building decision that can be made on the basis of information gathered from either conspecifics or heterospecifics. However, that this does not always occur shows that data from more species and locations are needed before generalizations can be made as to the use of such information [ 61 ].…”