Sex ratio in North American bird populations

Natural History & EvolutionIt is necessary to consider many different aspects of a species’ behavior, life cycle and morphology when attempting to discern a plausible reason for any significant sex ratio bias. The mechanisms of sex ratio evolution are still, for the most part, unknown to most researchers. This study intended to examine an existing data set and investigate any patterns in characteristics that were found among male- or female-biased populations. Data were provided by the Monitoring Avian Productivity and Survivorship Program and included birds banded in several regions of the United States. The original data set contained # North American bird species, and was cut down to 25 species of passerines and 1 woodpecker. This final data set was used to determine whether any of these 26 species had a significant sex ratio bias in their population. A skewed sex ratio was found in 11 species, and these populations were tested against those found to be unbiased in order to uncover any possible correlation between sex ratio and certain life history traits. No significant trends were observed, however, there were loose correlations between sex ratio bias and dichromatism and sex ratio bias and clutch size.http://deepblue.lib.umich.edu/bitstream/2027.42/57582/1/Shaney_Rachel_2007.pdfDescription of Shaney_Rachel_2007.pdf : Access restricted to U-M campus; authentication may be required