Abstract
Biologists know relatively little of how one of the most important avian phenotypic signals, feather coloration, may be affected by anthropogenic changes resulting from urbanization. We examined the relationship between urbanization and carotenoid-based plumage color of Northern Cardinals (Cardinalis cardinalis) in 13 riparian forests distributed across a rural-to-urban landscape gradient in central Ohio, USA. Feathers and morphometric measurements were collected from breeding territorial males (n = 129) and females (n = 145) during March–August 2006–2008. Plumage brightness of males, but not females, increased with body condition (i.e., size-adjusted mass) and declined with amount of urbanization surrounding forests in which cardinals bred. The extent plumage coloration reflected condition was partially mediated by landscape composition. Specifically, the relationship between brightness and body condition was most pronounced in the most rural landscapes. The interdependency of male coloration and body condition may be more relaxed in urban than rural landscapes if carotenoid-rich foods from anthropogenic and/or invasive sources are more available, or are accessible to birds across a wide range of condition.