Breeding success of the colonist species Bubulcus ibis (Linnaeus, 1758) and four native species

This work evaluated the breeding success of Bubulcus ibis (Ardeidae), Egretta thula, Nycticorax nycticorax, Phimosus infuscatus and Plegadis chihi in Rio Grande do Sul during two consecutive nesting seasons. Mean clutch size for B. ibis was 2.59 in 1998/1999 and 2.49 in 1999/2000. The species with both the smallest and largest clutch was P. infuscatus, with 2.04 in 1999/2000, and 3.16 in 1998/1999. The highest mean number of nestlings per nest was 2.86 for P. chihi in 1998/1999 and the lowest was 1.85 for B. ibis in 1998/1999 and P. infuscatus in 1999/2000. In both nesting seasons all the species had major success, laying three eggs and raising two nestlings, exept for B. ibis. The breeding success for P. chihi varied from 1.54 young/nest in 1998/1999 to 0.4 in 1999/2000, whereas B. ibis ranged from 1.16 in the first period to 0.99 in the second.