Status symbols of house sparrows

Saturday, June 5, 2010 - 11:20 in Biology & Nature

The size of the black breast bib - the badge - and bill colour of male House Sparrows change over the course of the year. Such ornaments usually signal quality and dominance of a male to his conspecifics and are correlated with his testosterone levels. These levels are generally higher before and during breeding season than for example during moult in autumn. A team of scientists at the Max Planck Institute for Ornithology in Seewiesen, Germany, recently demonstrated in a detailed study that only bill colour was correlated with the amount of testosterone in the blood. In contrast, the size of the badge was independent of hormone levels...

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