Effects of migrations on the nestedness structure of bird assemblages in cays of the Jardines de la Reina archipelago, Cuba

The nested subset hypothesis states that species in fragmented, less species–rich biotas are non–random subsets of those inhabiting richer sites. The effect of migration on these models has not been yet fully addressed. We compared the phenological stages of the community during the spring and fall migrations. Presence–absence data of bird species occurring at 43 cays of the Jardines de la Reina archipelago was compiled and two incidence matrices were built for fall and spring periods. The degree of nestedness was estimated based on the overlap and decreasing fill, and its significance was assessed by means of 1,000 replicates of four null models. Bird assemblages showed a higher number of species during fall (67) than they did in spring (51). They also showed a significant and stable pattern of nestedness, although this was slightly higher in spring. Seasonal fluctuations caused by migratory movements thus barely affected the nested structure of bird assemblages.