No evidence of skewed secondary sex ratios in nestlings of the Common Raven (Corvus corax) |
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Authors: | Sascha R?sner Kirsten Bogatz Hendrik Trapp Thomas Grünkorn and Roland Brandl |
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Institution: | (1) Department of Animal Ecology, Philipps University Marburg, Karl-von-Frisch Stra?e 8, 35043 Marburg, Germany;(2) Naust?dter Stra?e 7, 01665 Klipphausen-Riemsdorf, Germany;(3) BioConsultSH, Brinckmannstra?e 31, 25813 Husum, Germany |
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Abstract: | Many bird species adjust their offspring sex ratio as a response to environmental conditions or sexual dimorphism in size
and dispersal. Offspring sex ratios may therefore vary among populations depending on the different demographic and ecological
trajectories. We sampled Common Raven Corvus corax nestlings close to the fledging stage from three Central European regions to test for skewed secondary sex ratios and to
investigate differences in sex ratios between populations that differ in recent recolonization history and breeding densities.
Between 2005 and 2007, a total of 108 broods with 335 nestlings were sampled and their sex determined using molecular methods.
We observed a mean of 3.1 (±1.2) nestlings per brood with no differences among nesting sites, years or regions. Nestling sex
ratios were independent of the number of siblings. The overall secondary sex ratio was close to parity and did not differ
between the variably structured populations. |
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Keywords: | Corvidae Corvids Dispersal Secondary brood size Sexing Sex ratio |
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