Copulatory behaviour and paternity determined by DNA fingerprinting in kestrels: effects of cyclic food abundance

Abstract

It has been proposed that mate guarding is the primary paternity insurance in birds, and only those species in which the male is compelled to leave his mate unattended during the fertile period resort to frequent copulation as a means of assuring paternity. A higher frequency of both extra-pair copulation (EPC) and extra-pair paternity (EPP) has been predicted in non-guarding species. These predictions were examined in Eurasian kestrels, Falco tinnunculus, breeding in western Finland. During the course of a 3-year vole cycle, the mean within-pair copulation frequency was 0.72 per h and the mean number of extra-pair intrusions 0.07 per h. The proportion of EPCs was only 1% of copulations. The within-pair copulation frequency was higher in a year of increasing food abundance (1991) than in the years of decreasing (1992) and low food abundance (1990), although the kestrel breeding density was lower in 1990 than in 1991–1992. Males spent more time mate guarding in 1991–1992 than in 1990 (overall mean 40%). Single-locus DNA profiling revealed EPP in 7% of 27 broods and 5% of 112 offspring in 1991 but none in 1990 or 1992 (19 and 29 broods, respectively). Kestrel males successfully used both frequent pair copulation and mate guarding as complementary paternity guards. The low frequency of EPP may reflect the importance of male parental care in determining the reproductive success of raptors. Females may jeopardize future aid from their mates by soliciting EPCs from intruders. This strategy might markedly reduce female fitness, because the male is the main provider for female and young from before egg laying until the late nestling period.