Sharing mates and nest boxes is associated with female “friendship” in European starlings, Sturnus vulgaris.

Abstract

Breeding decisions in birds involve both mate and nest choice, and there is increasing evidence that social influences may modulate individual choices. Female preferences may be affected by other females' preferences and mutual choice cannot always be excluded, which makes the whole pattern more complex than assumed by most sexual selection models. Social transmission may be facilitated by particular social bonds, therefore prebreeding social networks may influence later mate choices. The other case where females share mate or resources is polygyny, generally viewed to only benefit males. If mutual benefits may arise then mechanisms should evolve to reduce the reproductive cost for females such as to reduce the cost of aggression by sharing their mate with a preferred same-sex social partner. We tested the hypothesis that females' mating decisions may be influenced by the prebreeding social network and that social partner relations established prior to breeding may share decisions (mate/sites) in a facultatively polygynous species, the European starling. Two experiments were designed to test the relative importance of male or nest by following the whole dynamics of the breeding cycle from the prebreeding period until mate and nest selection. In both cases socially isolated females tended to be excluded from breeding, while prebreeding social partners tended to share mates and to nest in close proximity, mate copying leading in some case to polygyny. The final pattern resulted both from female "likes and dislikes" and male preferences for some females. Aggressive interactions between females were rare. Vocal sharing between females may have been a clue for males as to the degree of social integration of these females.

Assessing Video Presentations as Environmental Enrichment for Laboratory Birds

“…However, when the experiment began, they were group housed in large aviaries, a context in which earlier studies did not detect SBs or ARBSs (e.g. [32], [33]). …”

Seasonal female brain plasticity in processing social vs. sexual vocal signals

“…Although seasonal changes occurred in these birds (e.g. beak color change, see below), the absence of nest boxes prevented them from breeding, and males did not display sexual behavior (Gwinner et al ., ; Henry et al ., ). Thus, females were in an appropriate seasonal environment and they showed visible seasonal characteristics, such as beak color changes, but they were not influenced by seasonal changes in male behavior (song, sexual display, etc.…”

“…Class‐II whistles are loud and simple structures made up of one or several notes that are produced by both males and females. They are mostly individual‐specific within a colony, but they can be shared by close social partners of the same sex in captivity (Gwinner et al ., ; Hausberger et al ., ; Poirier et al ., ; Henry et al ., ). Finally, Class‐III songs (also called warbling) are sung by both males and females in long, complex and quiet sequences composed of three parts containing motifs that are repeated one to several times with increasing tempo (Adret‐Hausberger & Jenkins, ; Eens et al ., ).…”

“…Female starlings interact vocally without these interactions leading to agonistic ones (Hausberger & Black, ; Henry & Hausberger, ). Social affinities change from the non‐breeding to the breeding season, intersexual pairs appearing only when nest availability allows males to attract females towards a given nest site (Feare, ; Gwinner et al ., ; Henry et al ., ). Mate attraction is characterized by particular displays (wing waving) and a clear increase in the production of particular song elements (high‐pitched trills: Verheyen, ; Henry et al ., ).…”

Social birds copy each other's lateral scans while monitoring group mates with low-acuity vision

“…We also asked whether copying was influenced by the sex composition of the group. Starlings are polygynous, with females forming groups of 2-4 individuals that mate exclusively with a single male and exclude other females from their group (Henry et al, 2013;Feare 1984). Males must compete with each other for access to these female groups (Feare 1984).…”