Sexual dimorphic colours and female choice in the common kestrel

Abstract

Common kestrels (Falco tinnunculus) exhibit pronounced sexual dimorphism in adult plumage colour. Since sexually dimorphic characteristics can be important in female choice and plumage colours represent signals of male quality in kestrels, we investigated whether female choice in captive common kestrels is influenced by the experimental manipulation of the grey colour of the male's tail and head feathers. In our experiment, females were allowed to choose between males with experimentally enhanced blue‐grey coloration (brighter than average) and control males (water treatment with no change in male colour patterns). We measured female preference as the frequency and duration of visits to each male (sitting on the perch or hanging on the partition wall). Overall, we did not detect any significant difference in frequency and duration of female visits between coloured and control males; however, individual females exhibited strong preferences for one of the two males, regardless of the colour of the male's tail and head. We briefly review hypotheses to explain why the plumage of the common kestrel is nevertheless sexually dimorphic.