Feather corticosterone in Northern Bald Ibis Geronticus eremita: a stable matrix over time able to predict reproductive success

Laura Monclús,Anais Carbajal,Manel Lopez-Bejar,Miguel Angel Quevedo,Oriol Tallo-Parra

doi:10.1007/s10336-019-01741-z

Abstract

Measuring corticosterone concentrations in feathers (FCC) has been increasingly used as an integrated index of bird’s response to stressors, offering valuable insights into subsequent carry-over effects. However, it is still unclear to what extent corticosterone levels deposited in feathers during the moulting period relate to individual physiology in high-energetic demanding situations. In addition, the stability and repeatability of FCC over the same feather generation and across successive generations are still unresolved questions. In this study, we assessed FCC in 24 captive Northern Bald Ibis, Geronticus eremita. We sampled body feathers on three occasions during two consecutive years (2015–2016) to explore within-individual stability of FCC in feathers grown during the same generation and test whether FCC was repeatable or varied between two consecutive generations. Then, we explored whether FCC (a) was associated with individual health status, (b) correlated with previous reproductive success and (c) was related to future reproductive success. Results showed high stability of FCC among feathers of the same generation, while FCC differed between successive generations. We also observed that FCC, age and health status were negatively associated with subsequent reproductive success the following season, while no association was found with previous reproductive success. Overall, our study supports the use of feathers as a stable measure of corticosterone over the same feather replacement generation and emphasizes the usefulness of FCC as a biomarker of subsequent reproductive success.

Highlights

Under some stress stimulus, corticosterone (CORT; the main glucocorticoid in birds) is released in blood circulation by the hypothalamic–pituitary–adrenal (HPA) axis which enables the animal to direct its normal activity to an “emergency” state (Wingfield et al 1998) and prioritize its resources towards self-maintenance (Jenni et al 2000)
The present study aimed to evaluate the usefulness of feather CORT concentrations (FCC) as a biomarker of fitness in an endangered bird species, the Northern Bald Ibis Geronticus eremita
We showed that FCC exhibits high stability across a single feather generation regardless of the feather sampling timepoint, which evidences the usefulness of body feathers as a stable metric

Summary

Introduction

Corticosterone (CORT; the main glucocorticoid in birds) is released in blood circulation by the hypothalamic–pituitary–adrenal (HPA) axis which enables the animal to direct its normal activity to an “emergency” state (Wingfield et al 1998) and prioritize its resources towards self-maintenance (Jenni et al 2000) (the so-called stress response) Despite this adaptive mechanism, the functioning of the HPA axis is altered when the stressor(s) is persistent or highly frequent resulting in elevated CORT levels in an extended period which can have detrimental consequences for the animal’s health, survival and reproduction (Romero et al 2009; Wingfield and Sapolsky 2003). Feathers represent a unique matrix because they provide an integrative, long-term and retrospective picture of physiology over time They incorporate CORT which was released during the whole period of feather growth, reflecting the HPA axis activity during this limited period of time which can extent from weeks to months (Bortolotti et al 2009; Jenni-Eiermann et al 2015; Aharon-Rotman et al 2015). It has been shown that small daily variations in baseline CORT levels do not affect global feather CORT concentrations (FCC) (Bortolotti et al 2008; Fairhurst et al 2013), which is similar to what it occurs in mammalian hair (Tallo-Parra et al 2016)

Methods

Results

Discussion

Conclusion