Nestling Provisioning by the Extremely Dichromatic Northern Cardinal

We measured feeding rates of nestlings during 143 h of observation on 23 pairs of the extremely dichromatic and socially monogamous Northern Cardinal (Cardinalis cardinalis). Males fed at higher rates than did females, both when measured as rate per brood and as rate per nestling. Only males maintained their feeding rate per nestling with an increase in brood size and increased their feeding effort as nestlings aged. Feeding efforts by mates were correlated, even when controlling for the effects of brood size. These results provide support both for hypotheses predicting subsantial male parental effort in socially monogamous birds and for the assortative mating hypothesis, predicting that birds of similar quality mate with one another. We reject the deflection hypothesis predicting low paternal provisioning effort in strongly dichromatic species and conclude that any cost to male cardinal ornamentation is not simply related to male activity at the nest.