Habitat selection and density of the Barbary partridge in Sardinia, Mediterranean Sea

The Barbary partridge is one of the four species of Alectoris found in Mediterranean Basin. Its range is restricted to Sardinia, northwestern Africa, Gibraltar, and Canary Islands. It is classified as SPEC3 because its population is declining; nonetheless, its ecology is poorly known. Our aims were to define the habitat factors linked to the species presence, and which affects the breeding density in northeastern Sardinia. Data were collected in the breeding seasons 2012 and 2013 carrying out 376 listening points in 34 study sites representative of the typical landscapes of the island. The habitat selection was assessed by generalized linear model with binomial error distribution following an information theoretic approach. In particular, the environmental variables concerning the land use cover, the landscape configuration, and the topography of the points with the species presence were compared with an equal number of availability points. The densities were estimated by distance sampling, and then, we formulated two multiple linear regressions, one for each year, relating densities with the environmental variables. The analyses showed that the species inhabits shrublands, garrigue, and meadows on slopes faced to east, especially between the sea level and 200 m, avoiding forests and northwestern slopes. In 2012 and 2013, we estimated 22.9 and 5.1 pairs per km2, respectively. It is likely that this change in densities is related to a lower singing activity of the males due to the bad weather conditions in the spring 2013