Résumé
Female ornamentation is frequently observed in animal species and is
sometimes found as more evolutionarily labile than male ornamentation. A
complex array of factors may explain its presence and variation. Here we
assessed the role of female cost of reproduction and paternal care. Both
factors have been pinpointed as important by theoretical studies but have
not been investigated yet in detail at the interspecific level. We worked
on 133 species of North temperate Passeriformes bird species for which
both the clutch volume – here taken as the proxy of female cost of
reproduction – and the amount of paternal care are relatively well known.
Using spectrometry, we measured the whole-body colored plumage patches and
quantified three metrics corresponding to brightness (i.e. achromatic
component), color chromaticity (i.e. intensity), and color volume (i.e.
diversity). We found a strong association between male and female color
metrics. Controlling for this association, we found additional small but
detectable effects of both cost of reproduction and paternal care. First,
females of species with more paternal care were slightly brighter. Second,
the interaction between the level of paternal care and egg volume was
correlated with female color intensity: females with more paternal care
tended to be more chromatic, only when their investment in reproduction
was low. Together these results suggest that female cost of reproduction
and paternal care are part of the multiple factors explaining variation of
female coloration, besides the strong covariation between male and female
coloration.