Color expression in experimentally regrown feathers of an overwintering migratory bird: implications for signaling and seasonal interactions.

Christopher M Tonra,Kristen L D Marini,Rebecca L Holberton,Matthew W Reudink,Ryan R Germain,Peter P Marra

doi:10.1002/ece3.994

Abstract

Plumage coloration in birds plays a critical role in communication and can be under selection throughout the annual cycle as a sexual and social signal. However, for migratory birds, little is known about the acquisition and maintenance of colorful plumage during the nonbreeding period. Winter habitat could influence the quality of colorful plumage, ultimately carrying over to influence sexual selection and social interactions during the breeding period. In addition to the annual growth of colorful feathers, feather loss from agonistic interactions or predator avoidance could require birds to replace colorful feathers in winter or experience plumage degradation. We hypothesized that conditions on the wintering grounds of migratory birds influence the quality of colorful plumage. We predicted that the quality of American redstart (Setophaga ruticilla) tail feathers regrown after experimental removal in Jamaica, West Indies, would be positively associated with habitat quality, body condition, and testosterone. Both yearling (SY) and adult (ASY) males regrew feathers with lower red chroma, suggesting reduced carotenoid content. While we did not observe a change in hue in ASY males, SY males shifted from yellow to orange plumage resembling experimentally regrown ASY feathers. We did not observe any effects of habitat, testosterone, or mass change. Our results demonstrate that redstarts are limited in their ability to adequately replace colorful plumage, regardless of habitat, in winter. Thus, feather loss on the nonbreeding grounds can affect social signals, potentially negatively carrying over to the breeding period.

Highlights

Visual signals in animals can play an essential role in an individual’s fitness (Maynard Smith and Harper 2003)
For colorful plumage limited by the environmental availability of pigments, social factors, or physical condition (e.g., Saks et al 2003; Barron et al 2013), dominant individuals in high-quality habitats should have an advantage in producing and maintaining high-quality plumage
We examine the influence of winter habitat quality, testosterone, and condition on the production and maintenance of colorful traits that are associated with breeding success in a migratory bird

Summary

Introduction

Visual signals in animals can play an essential role in an individual’s fitness (Maynard Smith and Harper 2003) Ornaments, such as colorful plumage, can serve as honest signals of individual quality which function in both inter(Kodric-Brown and Brown 1984; Hill 2006) and intrasexual communication (Maynard Smith and Harper 1988; McGraw and Hill 2000) and may be under selection across different phases of the annual cycle. Nonbreeding season conditions can carry over to influence multiple aspects of migration and breeding season performance (e.g., Bearhop et al 2004; Gunnarsson et al 2005; Reudink et al 2009a; Tonra et al 2011) Revealing such seasonal interactions (Marra et al 1998; Runge and Marra 2005) is critical to understanding the ecology of migratory birds. No study to date has examined how stationary nonbreeding (hereafter: winter) habitat effects on spectral signal production may carry over to influence breeding success (but see Saino et al 2004; Sorensen et al 2010 for studies of ornament size)

Methods

Results

Conclusion