Patterns of distribution, abundance and species richness of terrestrial bird fauna in La Palma (Canary islands)

Abstract

We estimate the population size and density, habitat preferences, habitat breadth and probable population trends in the last 25-15 years of the diurnal terrestrial bird species breeding in La Palma island (Canary islands). Data were obtained in a large extensive census program carried out during the 2007 nesting period using line transects that allowed detectability estimations. We also explored patterns of species richness both at inter-habitat and local scale. Local species richness (species per 0.5 km transects) showed an important geographical component, increasing from south to north, from west to east, and reaching maximum values at altitudes around 600-1,000 m a.s.l. It was also positively related to vegetation development (specially in the herbaceous and shrub layer), and negatively associated with urbanization and agriculture. Total bird density reached the highest figures in the ‘monteverde’ (laurel and heath forests ca. 650 aves/km²), and in the transition pinewoods-laurel forests (509 aves/km²), while the lowest figures were recorded in high altitude shrublands (153 aves/km²) and recent lava fields (58 aves/km²). The bird species with lower population sizes are Falco [peregrinus] pelegrinoides, Burhinus oedicnemus distinctus, Upupa epops, Carduelis carduelis, Miliaria calandra and Petronia petronia, while the last five species have undergone more negative population trends in the last 15-25 years.