Reproductive biology of Thalasseus sandvicensis from Cardos Island, Florianópolis, Santa Catarina, Brazil

The occurrence, abundance and reproductive aspects of Thalasseus sandvicensis has been studied, mainly on the coast of Espírito Santo, Santa Catarina and Rio Grande do Sul, Brazil. This work aims to provide novel information on the reproductive ecology of the Cayenne Tern from the Cardos Island, Florianópolis, Brazil. During the reproductive period (May-October) in the breeding seasons of 2003, 2005 and 2006, we carried out daily surveys in order to characterize the population structure, and estimate the reproductive and hatching success of this species. The first adults were seen between April to May, and the first eggs were laid in May-June with a total reproductive effort ranging between 50 to 174 nests. This species incubated eggs during 25.0 ± 0.5 days and the hatching success ranged from 75% in 2003 to 90% in 2005, with the first chicks appearing from June. Coragyps atratus and Polyborus plancus were the main predators, predating mainly on eggs and juveniles. The reproductive success ranged from 5.0% in 2006 to 48.0% in 2003. The low human pressure and absence of natural predators allowed the regular occupation of this breeding site and a satisfactory reproductive performance. Therefore, Cardos Island constitute an important area for conservation of Cayenne terns in Brazil.