Plumage characteristics as an indicator of male parental quality in the American Kestrel

How females pair with respect to the plumage and provisioning characteristics of males, and its fitness consequences, was studied in the American Kestrel Falco sparverius in east central Pennsylvania, USA. Within a 100 km(2) area where pairing was studied, on the day females formed a pair bond they had approximately 3.4 unmated males to choose from. No male trait was clearly related to the time males had to wait before obtaining females. Indeed, the scarcity of unmated males together with extremely fast pairing (the pairs were usually formed within a day of males' arrival) suggest limited mating options for females. Male plumage brightness was related to age, adult males being brighter than yearlings. Early laying by females was associated with bright plumage of males, and high hatching success and food provisioning rate to nestlings were negatively correlated with the width of the subterminal band of yearling males. Males with bright plumage and a narrow subterminal tail band produced the most fledglings. This study indicates that plumage characteristics may reveal males' parental quality; plumage brightness predicts age and thus experience, and a narrow subterminal tail band predicts foraging ability especially of young, inexperienced males. Consequently, females mated to males with bright plumage color or with narrow subterminal tail band gain reproductive success. The results support the direct process of sexual selection, even though indirect processes may also exist.