Breeding success of Black-crowned Night Heron (Nycticorax nycticorax), Little Egret (Egretta garzetta) and Cattle Egret (Bubulcus ibis) (Aves: Ardeidae) in relation to nest height in the South Caspian Sea

Abstract

Breeding success was investigated in a mixed colony of three species of Ardeidae (Black-crowned Night Heron, Nycticorax nycticorax; Little Egret, Egretta garzetta; and Cattle Egret, Bubulcus ibis) in the Karfestan colony, south Caspian Sea, during the 2006 breeding season. Black-crowned Night Herons occupied higher locations for nesting (4.39 ± 1.44 m) than both Little Egrets (3.07 ± 1 m) and Cattle Egrets (2.8 ± 0.84 m). Clutch size appeared to be independent of the height of the nest from the ground in all species. Mean breeding success was 0.82 ± 0.24, 0.80 ± 0.16 and 0.77 ± 0.17 in the Black-crowned Night Heron, Little Egret and Cattle Egret respectively. Overall breeding success did not vary significantly among the three species. Fledging success and overall breeding success were associated with nest height in the Black-crowned Night Heron, with a tendency for the higher nests to be more successful. Nest height was also correlated with fledging success in the Cattle Egret but had no effect on breeding success in the Little Egret.