Testosterone might not be necessary to support female aggression in incubating northern cardinals

Abstract

Keywords: aggressionCardinalis cardinalis corticosterone female incubation maternal aggression nest defence northern cardinal testosterone Testosterone's (T) influence on male aggression has been well established in many vertebrate species, but the impact of T on female aggressive behaviour is poorly understood. Among birds, a link between T and female aggression is plausible, as females of many species exhibit a seasonal peak in T concentrations at the onset of breeding when social instability is greatest and they may have circulating T through much of the breeding season. However, investigations examining the relationship between T and female aggression are few and have yielded conflicting results, with experimentally or endogenously elevated T supporting aggressive behaviour in females of some species but not others, and T elevating with aggression at some points of the reproductive cycle but not others. We examined the relationship between endogenous levels of T and female aggression in the northern cardinal, Cardinalis cardinalis, a resident temperate species in which pairs exhibit prolonged territoriality and females have measurable levels of T year-round, including all stages of reproduction (incubation, nestling feeding, etc.). Using simulated nest intrusions, we assessed aggressive responses of incubating females to intrasexual 'intruders' at the nest and quantified T levels after each aggressive encounter. Displays of aggression towards 'intruders' varied among females; yet, individuals showing greater levels of aggression did not demonstrate higher levels of T. These results imply that T might not support maternal aggression in this species.

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.…”

Melanin ornament brightness and aggression at the nest in female Northern Cardinals (Cardinalis cardinalis)

“…In the Northern Cardinal past work has found that carotenoid-based plumage ornaments can indicate body size and condition ; however, this has not been the case for melanin-based ornaments. Furthermore, neither size nor condition has been found to covary with hormone production (Jawor 2007, DeVries et al 2011, territory and nest defense (DeVries et al 2012(DeVries et al , 2015, or parental care behavior , DeVries and Jawor 2013 in the Northern Cardinal. Previous findings concerning condition, size, and behavior are from both the current study population in Mississippi and the Ohio population previously studied and suggest that body size and condition may not play a strong factor in aggressive behavior in this species.…”

“…Intrasexual aggressive behavior was assessed using an SNI based on methods described in and modified slightly based on DeVries et al (2015). On the day of SNI assessment, between 0600 and 1000 hr, a female Northern Cardinal decoy (mounted in a perching posture) was placed 1 m from the nest of a focal female after the focal female had left for a break in incubation.…”

Full Issue

“…In the Northern Cardinal past work has found that carotenoid-based plumage ornaments can indicate body size and condition ; however, this has not been the case for melanin-based ornaments. Furthermore, neither size nor condition has been found to covary with hormone production (Jawor 2007, DeVries et al 2011, territory and nest defense (DeVries et al 2012(DeVries et al , 2015, or parental care behavior , DeVries and Jawor 2013 in the Northern Cardinal. Previous findings concerning condition, size, and behavior are from both the current study population in Mississippi and the Ohio population previously studied and suggest that body size and condition may not play a strong factor in aggressive behavior in this species.…”

“…Here, we investigated how a melanin-pigmented plumage ornament, the face mask, covaries with intrasexual aggression in female Northern Cardinals (Cardinalis cardinalis). Female cardinals display both intrasexual and intersexual aggression over territories and nesting resources , DeVries et al 2015. In female cardinals, previous work found that face mask expression co-varied with aggressive behavior at the nest ).…”