Habitat and niche determinants of the organization of two bird communities in northern Italy

Abstract

The organization of two birds communities (passeriformes and piriformes) has been studied at two sites in northwestern Italy in order to identify better those factors that, at different ecological levels, may afford interspecific coexistence. Apart from minor differences between the two communities mostly due to the different vegetation structure and composition of the two study areas, it has been shown that the ecological organization of these bird communities depends on common niche and habitat factors. The former mainly work to discriminate, especially in the autumn and winter, several groups of species which are both ecological and systematic assemblages, whereas the latter, independently of the above‐mentioned groups of species, further increase segregation according to habitat gradients. With regard to niche, foraging seems to discriminate groups better than do singing and resting activities.

Key words:

• Community
• Habitat
• Interspecific coexistence
• Niche