Sexual size dimorphism and its effect on load size and loading efficiency in wheatears Oenanthe oenanthe

Abstract:

In this study we have tried to relate sexual dimorphism in Wheaters Oenanthe oenanthe, especially with respect to bill morphology, to their capabilities for loading prey in their bills for later transport to their young. We measured 91 museum skins (55 males, 36 females) of Swedish Wheatears plus 6 males and 5 females captured in the wild in our study area with respect to bill length, bill depth and bill width, wing length, tarsus length and tail length. A stepwise discriminant analysis was performed on all measurements. Bill length and wing length are the two variables that best discriminate between the sexes. Males are significantly larger in most characters, bill length included. We also recorded the number of maggots loaded by four pairs of Wheatears on each visit to our experimental feeders and the time spent by them at the feeders before flying to their nests with the loads. All males of the experimental pairs had …

Año de publicación:

1983

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