Males of a single-brooded tropical bird species do not show increases in testosterone during social challenges

Up to the challenge? Hormonal and behavioral responses of free-ranging male Cassin's Sparrows, Peucaea cassinii, to conspecific song playback

“…Thus, as in the Song Sparrow, visual (and potentially tactile) stimulation may be necessary to induce a hormonal response in male Cassin's Sparrows. It should, however, be pointed out that as described above, plasma T does not always increase following exposure to STI consisting of SPB together with a decoy Charlier et al, 2009;Gill et al, 2008;Moore et al, 2004;Schwabl et al, 2005). In two species (Great and Blue Tits), this exposure in fact decreases plasma T Van Duyse et al, 2004).…”

“…However, other studies found no influence of single or repeated social interactions on plasma androgens (birds: Addis et al, 2010;Gill et al, 2008;lizards: Klukowski et al, 1998;Thompson and Moore, 1992) whereas in the Great Tit, Parus major, and Blue Tit, Cyanistes caeruleus, plasma T decreased in response to STI Van Duyse et al, 2004;reviews: Goymann et al, 2007;Goymann, 2009). To reconcile these apparent discrepancies, it has been proposed that androgen responsiveness to a social challenge varies as a function of a number of factors including the mating system (Wingfield et al, 1990;single-vs. multiple broodedness: Landys et al, 2007), the contribution of males to incubation (Hirschenhauser et al, 2003), and the duration of the breeding season (Goymann, 2009).…”

“…In two species (Great and Blue Tits), this exposure in fact decreases plasma T Van Duyse et al, 2004). A combined auditory and visual challenge is, therefore, frequently insufficient or altogether ineffective to rapidly elevate plasma T. It has also been proposed that the number of broods regulates the response to STI, with males of multi-brooded but not single-brooded species increasing plasma T in response to STI (Gill et al, 2008;Landys et al, 2007). Cassin's Sparrows in part of their range (Texas; Schnase et al, 1991) are thought to commonly be double-brooded, but the reproductive biology of the species remains incompletely known and it has not been determined whether this is the case also for sparrows of the northern population investigated here.…”

“…One commonly used experimental procedure is to expose individuals to simulated territorial intrusions (STI) consisting of pre-recorded conspecific vocalizations combined with a live (Charlier et al, 2009;Hau and Beebe, 2011;Landys et al, 2007;Moore et al, 2004;Wingfield, 1994a) or stuffed Silverin et al, 2004) decoy. Exposure to STI often elicits a strong aggressive response (Gill et al, 2008;Klukowski and Nelson, 1998;Wingfield, 1994b) and, in some situations, a rapid (within minutes) increase in plasma testosterone (T; Ros et al, 2002;Wingfield, 1984Wingfield, , 1994b. In free-ranging Song Sparrows, Melospiza melodia, exposure to conspecific song playback alone or with a live decoy bird has a similar stimulatory effect on aggressive behavior, but plasma T increases significantly only in sparrows that are exposed to both stimuli (Wingfield and Wada, 1989).…”

Hormone levels predict individual differences in reproductive success in a passerine bird

“…(c) Hormone assays Circulating Cort concentrations were determined in a single radioimmunoassay [46]. Cort antibody was purchased from Esoterix Endocrinology, CA, USA.…”