No consistent female preference for higher crown UV reflectance in Blue Tits Cyanistes caeruleus: a mate choice experiment

Abstract

Although male UV structural plumage coloration can indicate male quality (e.g. Keyser & Hill 2000) and female reproductive investment strategies (e.g. Sheldon et al. 1999, Griffith et al. 2003), unambiguous evidence that such plumage is a direct target of female choice is still lacking. A straightforward way of testing this is by conducting controlled mate choice experiments that exclude confounding factors such as male–male competition or territory quality. The first experiments on the role of structural colours in mate choice used UV-blocking windows (e.g. Bennett et al. 1996, Hunt et al. 1999), thereby completely removing male UV reflectance. A better approach is to vary UV reflectance within the natural range under natural light conditions. Only two such mate choice experiments have been undertaken to date (Ballentine & Hill 2003, Liu et al. 2007). In neither study did females show a preference for more UV-ornamented males. In the present study, we manipulated crown reflectance of first-year male Blue Tits Cyanistes caeruleus to test the hypothesis that females prefer males with a higher crown UV reflectance, as predicted by patterns of sex allocation, paternity and female parental investment in this species (Johnsen et al. 2005, Delhey et al. 2007a,b). In a mate choice experiment, females were offered a choice of two males (matched for yellow breast colour), one with a UV-reduced crown reflectance and one control-manipulated male. The results indicated that female preference was inconsistent and may be context-dependent