Spatial distribution patterns of terrestrial bird assemblages on islands of the Sabana–Camagüey Archipelago, Cuba: evaluating nestedness and co–occurrence patterns

Abstract

Using distribution data of 131 terrestrial bird species on 17 islands of the Archipelago Sabana–Camagüey, Cuba, we tested for non–randomness in presence–absence matrices with respect to co–occurrence and nestedness. We conducted separate analyses for the whole assemblage and sub–matrices according to trophic levels and residence status (breeding and migratory). We also explored the influence of weighting factors such as island area and isolation. The C–occurrence analyses were susceptible to the species subsets and the weighting factors. Unweighted analyses revealed a significant negative co–occurrence pattern for the entire assemblage and for most sub–matrices. The area weighted analyses always indicated strong non–random structure. However, an analysis with intra–guild species pairs showed that most pairs were randomly assembled; very few pairs had a significant segregated pattern. Bird assemblages followed a nested subset structure across islands. Nestedness was strongly correlated with area and unrelated with island isolation. Overall, this study suggests that terrestrial bird assemblages were shaped by extinction processes mediated through area effects rather than interspecific trophic guild competition. Data suggest that conservation of largest islands will guarantee high terrestrial bird richness on the archipelago.