Experimental evidence of the territorial defense, hypothesis in insular Blue Tits
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- Perret, P. & Blondel, J. Experientia (1993) 49: 94. doi:10.1007/BF01928800
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Many insular vertebrates have unusually high population densities and are characterized by behavioural shifts including reduced territory size and reduced situation-specific aggressiveness. Compared to their mainland counterparts, Blue Tits on the island of Corsica exhibit many traits that fit the trends observed in crowded insular populations. We demonstrate from behavioural observations in aviaries and from hormone measurements that Corsican its are less aggressive than mainland ones. These shifts, as well as changes in reproductive patterns, support the defense hypothesis.