Long-term studies on productivity of Roseate Terns and Lesser Noddies on Aride Island, Seychelles

Abstract

This paper summarises up to 16 years of data on the productivity of Roseate Terns and Lesser Noddies on Aride Island, Seychelles, in order to assess: (1) the magnitude of variation in reproductive parameters, (2) the factors influencing their breeding success, and (3) whether common factors influenced the productivity of the two species. With the exception of 2002, the productivity of Lesser Noddies on Aride Island was always higher than that of Roseate Terns. The frequent mass mortalities of chicks on Aride were more common for Roseate Terns (an almost null productivity occurred in 44% of the years) than for Lesser Noddies (productivity less than 0.10 chicks per breeding pair occurred in only 20% of the years). Hatching success of both species was positively correlated, but there was no correlation for productivity, which suggests that stochastic variation in short-term food availability affected both species differently. Our results indicate that food shortage is the main factor explaining the breeding success of both species on Aride; the impact of other factors, such as tick infestation, depended upon the extent of food shortage. The underlying causes of food shortage are difficult to predict, although annual variation in marine productivity seems to be the ultimate factor determining productivity of Roseate Terns and Lesser Noddies.

Ostrich 2007, 78(2): 443–447