Mag. Katharina Mahr

Karharina Mahr

PDF im Hochschulschriften-Service der Universität Wien

Do ornaments effect parental investment?

Differential allocation hypothesis (DAH) predicts that individuals will invest in parental care to the offspring of the current reproduction according to their own and their current mate’s quality. This applies to females in most cases, but also to males at least in cases in which female quality is crucial for offspring survival and the males’ parental investment is high. Male differential allocation may at least partly explain why females of several species are ornamented. However, male differential allocation has been tested in only very few experimental studies, revealing contradictory results. We conducted a field experiment to test whether male blue tits (Parus caeruleus) allocate their parental effort in relation to female ornamentation (ultraviolet coloration of the blue crown plumage), as predicted by the DAH. We reduced the UV-reflectance in a sample of females and compared the parental care (feeding investment, nest defence intensity) of their mates with the parental care of males paired to females, which were manipulated with avian preen gland fat. Our results revealed a significant effect of female treatment on male feeding trips and food load provided per nestling. As predicted by the DAH our results demonstrate that males invested less in parental effort when paired to UV-reduced females than to control females. Tests of the male nest defence behaviour did not indicate differences between the two female groups; furthermore we did not find differences in nestling body mass between the two female groups. However, to our knowledge, this is one of the first studies providing support for male differential allocation as response to female ornamentation.