A TEST OF MALE MATING AND HUNTING SUCCESS IN THE KESTREL - THE ADVANTAGES OF SMALLNESS

We tested female choice for male wing and tarsus length and body mass in the kestrel (Falco tinnunculus), a species in which males average a bout 10% smaller than females. We also studied how male characters are related to their hunting success. In the laboratory, females preferre d lighter males with shorter tarsi as mates, if the difference in thos e characters between competing males was larger than average. Lighter and shorter-winged males seemed to be better hunters than heavier and longer-winged males. Field observations in a year in which voles were scarce suggested that shorter-winged males were also better food provi ders in courtship feeding than longer-winged males, although in good v ole years such a relationship was not found. We argue that females may prefer to pair with smaller males, because they have higher flight pe rformance and better hunting success than heavier males. By doing so, females may gain direct breeding advantages. We conclude that both fem ale choosiness and the hunting efficiency of males well contribute to reversed sexual size dimorphism (RSD, females larger than males) in th e kestrel.