Red coloration of male northern cardinals correlates with mate quality and territory quality

I investigate how mate quality and territory quality influence an extravagant ornament in a socially monogamous species that defends multipurpose territories. Northern cardinals (Cardinalis cardinalis) are a highly dichromatic, socially monogamous species, and males are a brilliant red. I conducted a 3-year field study of northern cardinals and found that redder males produced more offspring in a breeding season. Two selective factors mediated this fitness gain. Redder males were paired with earlier breeding females, an established measure of mate quality in birds. Second, redder males obtained territories of higher quality, as measured by vegetation density. Interactions among these factors were also important in explaining variance in male reproductive success. Multivariate analysis indicated that earlier breeding increased reproductive success independent of territory quality In turn, territory quality contributed to male reproductive success through its effect on nest survival and possibly through its role in attracting an earlier breeding female.