Nest Defence Behaviour and Testosterone Levels in Female Pied Flycatchers

Abstract

Nesting holes are a scarce resource for obligated cavity-nesting birds and an important selective force for the evolution of aggressive female behaviours, which may be mediated by testosterone (T) levels. It is known that during periods of intense intrasexual competition such as initial breeding stages, females are highly aggressive towards intruding females. Here, we studied the implications of T levels for female-female competition by comparing levels of aggressiveness towards simulated female intruders (decoys) in two populations of the pied flycatcher (Ficedula hypoleuca) with a marked difference in breeding density. To this end, we exposed free-living females to simulated territorial intrusions during 30 min when nest construction was almost complete. T levels of females were measured at the beginning of incubation under the assumption that they are positively associated with T levels during nest building. We also related aggressiveness to T levels in both populations. Furthermore, we aimed at detecting whether variation of T levels may explain female incubation attendance. Females showed higher T levels in the populations where pied flycatchers were exposed to a higher likelihood of conspecific interactions (high breeding density) than in the population with low breeding density. Female territorial presence, vigilance at the nest box and proximity to decoys were negatively related to circulating T levels in the high-density population, but not in the low-density population. Differences in T levels between populations did not result in differences in female incubation attendance, but T levels were negatively related to the incubation attendance in females from the population showing high T levels. In our populations, T levels in females prior to laying reflect the need to defend nesting cavities which is higher at high breeding density and in subdominant females. High T levels are costly in terms of incubation attendance.Ethology 121 (2015) 946-957

Social environment during egg laying: Changes in plasma hormones with no consequences for yolk hormones or fecundity in female Japanese quail, Coturnix japonica

“…The link between plasma androgen levels and intra-sexual competition has been extensively studied under the “challenge hypothesis” [21], which states that, during reproduction, plasma T correlates positively with male-male competition. In females, although there are fewer studies than in males, similar hormonal responses to social challenges have been observed [16, 18, 22, 23], yet studies have also reported no link, or even negative correlations between female-female competition and circulating plasma androgen levels [19, 24–27]. Given these contradictory findings, further research is required to clarify the relationship between intra-sexual competition and circulating androgens in females.…”

Phenotypic plasticity in breeding plumage signals in both sexes of a migratory bird: responses to breeding conditions

“…UV reflectance of white patches has been analyzed in other studies of the species (Lehtonen et al , Sirkiä and Laaksonen ). In this study we focus on the area of these plumage patches as in other studies of the species (Galván and Moreno , Lehtonen et al , Lobato et al , Moreno et al , , , Cantarero et al , , Laaksonen et al , Sirkiä et al , Plaza et al ). Moreover, we have previously shown that area and UV reflectance of wing patches are positively correlated, at least in females (Cantarero et al ).…”

Effects of the maternal and current social environment on female body mass and reproductive traits in Japanese quail (Coturnix japonica)

“…Effects of the social environment on female endocrine physiology and body mass (Bonenfant et al, 2009;DeVries et al, 2003;Eisenegger et al, 2011) provide proximate mechanisms through which reproduction and offspring can be affected. In birds, increasing group size, for example, is thought to exacerbate intraspecific competition, which can affect body mass (Asghar Saki et al, 2012;Keeling et al, 2003;Onbasilar and Aksoy, 2005) and circulating levels of steroid hormones such as corticosterone and androgens (Cantarero et al, 2015;Cunningham et al, 1987;Koelkebeck and Cain, 1984;Langmore et al, 2002;Mazuc et al, 2003;Onbasilar and Aksoy, 2005;Raouf et al, 2006;Smith et al, 2005). In Japanese quail, frequent changes in the group composition of breeding females are thought to reflect increased social densities and lead to elevated plasma corticosterone concentrations (Guibert et al, 2010).…”