Feather steroid hormone concentrations in relation to age, sex, and molting time in a long‐distance migratory passerine

Abstract

In birds, concentrations of testosterone (T) and corticosterone (Cort) are closely connected with many morphological, behavioral, and other physiological traits, including reproduction, metabolism, immunity, and fitness. The direction of the effect of these hormones on above‐mentioned traits, and the potential feedback between hormones are in general unclear; in addition, knowledge on how age and sex can affect T and Cort concentrations is still inconsistent. Our study used a novel method to analyze testosterone and corticosterone in feathers (Tf, Cortf) based on the precolumn chemical derivatization of hormones before liquid chromatography–tandem mass spectrometry (LC‐MS/MS) analysis. Unlike previously used methods (RIA, EIA), our analytical procedure allows simultaneous analysis of both hormones from small amounts of feathers (4–25 mg) and, thus, overcomes the problem of insufficient detection limits. We applied this method to reveal associations between Tf and Cortf hormone concentrations and feather growth, age, and sex in feathers grown during the postbreeding (flanks) and prebreeding (tails) periods in barn swallows (Hirundo rustica). There was neither a correlation between prebreeding and postbreeding Tf, nor between prebreeding and postbreeding Cortf. Tail Cortf concentrations were negatively associated with tail feather growth rates. Feather hormone concentrations were correlated in the prebreeding period, negatively in males but positively in females. Both Cortf and Tf were higher in young birds compared to older ones, indicating either an age‐related decrease in hormone concentrations within individuals, or the selective disappearance of individuals with high steroid concentrations. Males and females did not differ in Cortf, but Tf concentrations were higher in males than females, particularly during the prebreeding period. In this study, we provide an effective method for analyzing hormones in feathers in an ecological context, especially in situations when the total amount of feathers available for the analysis is limited.

Inter-annual stability and age-dependent changes in plasma testosterone levels in a longitudinally monitored free-living passerine bird

“…Similarly, in longed-lived common terns ( Sterna hirundo), male plasma T levels first sharply increased and reached a peak at maturity (2-5 years), the started to moderately decrease with age (Nisbet et al, 1999). An analogous trend suggesting the effects of hormonal senescence was also described for feather T levels in barn swallows (Adámková et al 2019). These results are in contrast with most other avian studies (none using a longitudinal design), which have not detected any age-related changes in male T levels.…”

“…While physiologically important (Goymann & Wingfield, 2014), no longitudinal study has yet examined whether female T undergoes age-related changes through ontogeny in birds. Recently, female T levels have been shown to decline with age in two passerines, the pied flycatcher ( Ficedula hypoleuca; Moreno et al 2014) and the barn swallow (Adámková et al, 2019) both using cross-sectional data. In contrast, in our study female plasma T levels remained stable during their lifetime.…”

“…This may result from the fact that the effects of T on bird coloration are often complex and condition-dependent, and can therefore adopt variable directions or remain entirely lacking (Fargallo et al 2007; Alonso-Alvarez et al 2009; Rull et al 2016). Furthermore, plasma T levels influence pigment deposition into ornaments only during the moulting period in the previous season (Kimball, 2006), so the absence of these relationships may also result from low individual inter-seasonal T rank stability, which remains unknown (Kempenaers et al 2008; but see Adámková et al 2019). However, we observed a strong positive association between T plasma levels and the brightness of the yellow plumage ornament in re-captured males.…”

“…A single study used longitudinal data which revealed a peak for middle-age birds and a subsequent age-related decline in T levels in the Florida scrub-jay ( Aphelocoma coerulescens; Wilcoxen, Bridge, Boughton, Hahn, & Schoech, 2013). In all other (cohort) studies, age-related decreases in T levels have only been detected in the Japanese quail ( Coturnix japonica; Balthazart et al 1984), the common term ( Sterna hirundo; Nisbet et al 1999), the pied flycatcher ( Ficedula hypoleuca; Moreno et al 2014) and the barn swallow ( Hirundo rustica; Adámková et al 2019). In contrast, a majority of avian studies based on comparisons of young vs adult individuals (Belthoff et al 1994; Schoech et al 1996; Madsen et al 2007) or cross-sectional data (Smith et al 2005; Peters et al 2002) reported no effect of age on male T levels.…”

Effects of feather processing methods on quantity of extracted corticosterone in broiler chickens

“…In our previous laboratory research on the methodological validation of using a bead beater (BB) and surgical scissors (SS) in the hair of Hanwoo cattle, revealed the importance of hair processing method in obtaining constant and reliable hair cortisol [18]. Equally, some literature indicated methods of pulverizing feather into a powder or finely chopping the feather into small pieces for extraction of corticosterone include a) using the SS [4,17], b) the ball mill [9,19,20], and c) the BB [9]. Each of these processing methods has claimed to have some limitations of using, such as long processing time for chopping into small pieces or pulverization of feathers, and homogenization [9,21] that could possibly confound interpretation of the result.…”