Family morph matters: factors determining survival and recruitment in a long-lived polymorphic raptor

From an evolutionary perspective recruitment into the breeding population represents one of the most important life history stages and ultimately determines the effective population size. In order to contribute to the next generation, offspring must survive to sexual maturity, secure a territory and find a mate. In this study we explore factors influencing both offspring survival and their subsequent recruitment into the local breeding population in a long-lived urban raptor, the black sparrowhawk (Accipiter melanoleucus). Adult black sparrowhawks show discrete colour polymorphism (dark and light morphs) and in South Africa morphs are distributed clinally with the highest proportion of dark morphs (c.75%) present in our study population on the Cape Peninsula. Parental morph was associated with both survival and recruitment. For survival, parental morph combination was important – with young produced by pairs of contrasting morphs having higher survival rates than young fledged from like...