The influence of relatedness and display effort on the mate choice of captive female American kestrels

Female American kestrels, Falco sparverius, were given the opportunity to choose between two males differing with respect to relatedness and nestling experience . Females did not discriminate against sibling males when choosing mates . Male display activity (number of nestbox inspections) was recorded and significantly more females chose the most active male . American kestrels suffer high yearly mortality, and the scarcity of suitable nesting cavities limits their breeding densities . Thus, there may be little selection pressure for incest avoidance by means of kin recognition . However, male display effort may play a role in the choice of mates . The primary goal of mate choice studies has been to with certain members of the opposite sex than with demonstrate that natural selection favours mechaothers' . Behaviour indicative of American kestrel nisms enabling individuals to choose mates of the pair-bond formation during the pre-nesting period highest quality . Selection pressures have operated has been well documented (Willoughby & Cade in a variety of ways on different species to produce 1964 ; Balgooyen 1976) and is readily exhibited in a continuum of discriminatory abilities. These captivity (Willoughby & Cade 1964; Olendorff range from indiscriminate mass spawnings of cer1968) . tain fish (Bond 1979) to finely tuned choice mechanisms involving genotypes, such as kin recognition (Bateson 1983). Not surprisingly, investigators have revealed a variety of cues organisms use to METHODS choose mates. Grant & Colgan (1983) reviewed factors influencing female choice, including A description of the annual maintenance and resources provided (e .g . courtship feeding; Nisbet captive breeding procedures for the McGill kestrel 1973) and defended (e .g . nest sites; Pleszczynska colony is provided by Bird (1982) . In the 1983 and 1978; Garson 1980) by the male . These factors 1984 breeding seasons, a total of 35 sexually mature reflect aspects of male quality that directly affect females from 22 clutches was studied . Females female fitness . (N=31) from 18 clutches were reared with their In contrast, phenotypic markers of genetic siblings by their natural parents . Four females, quality may affect the fitness of a female's offspring from four clutches, were separated and reared (Howard 1978). Examples include body size (Hanindividually by foster parents . In the fall the birds son & Smith 1967 ; McCauley & Wade 1978) and were overwintered in flight pens measuring relatedness (Bateson 1982). We investigated the 7 . 5 x 6. 5 x 2. 5 m, each containing up to 30 indiinfluence of relatedness and male display effort on viduals of the same sex . Birds were fed day-old the mate choices of captive female American cockerels supplemented every 2 days with dietary kestrels, Falco sparverius. Research was facilitated limestone or with SA-37 vitamin/mineral suppleby the availability of a large pedigreed colony ments (Roger-STB Division of BTI Products, Inc ., maintained at the Macdonald Raptor Research Montreal, Quebec) every other day . All birds were Centre of McGill University (Bird 1982) . This exposed to a natural photoperiod . species breeds readily in captivity and is sexually From 25 April to 17 May 1983, and from 9 April mature in its first spring . to 2 May 1984, females were given the opportunity Halliday (1983) defined mate choice as `any to choose between a male sibling and an unrelated pattern of behaviour, shown by members of one male of the same age and breeding experience . Each sex, that leads to their being more likely to mate female was tested once with each of her male 0003-3472/89/010112+06 $03 .00/0 L© 1989 The Association for the Study of Animal Behaviour