Habitat selection and density-dependent relationships in spatial occupancy by male Little Bustards Tetrax tetrax

Abstract

This study analyses habitat selection by male Little Bustards Tetrax tetrax of a central Spanish population within their display sites during two consecutive breeding seasons. The areas of sexual display sites were determined by applying minimum convex polygons (MCP) to locations of individual males throughout the 2001 and 2002 breeding seasons. Habitat selection was addressed by means of a compositional analysis. The effects of variables related to phenology and to the density of conspecifics were examined, assuming an ideal free distribution of organisms. The spatial distribution of display areas was also analysed. During both years male Little Bustards showed a significant preference for old and same-year fallows, these offering both shelter and food. Contrary to what was expected, individuals did not select lower quality habitats when conspecific density increased or when areas were occupied earlier, suggesting that the population was not saturated. Display sites were not clumped, showing that in this population the Little Bustard may not employ a lek mating system, even though certain requirements of an exploded lek system - the inclusion in territories of particular habitat types that females could potentially use - were met. Our results emphasise the importance of agrarian substrates in determining occupation by this species, a finding with direct implications for the conservation of populations given that the agrarian landscape is on a sufficiently large scale for management measures to be introduced.