Diet of chicks of Cattle Egrets Bubulcus ibis in the lower Soummam valley, Algeria

Abstract

The diet of Cattle Egret chicks in the lower Soummam valley, Algeria, was investigated in 1998 and 2006, when 145 and 23 regurgitates were collected, respectively. In 1998, 1 698 individual prey items were identified. Insects formed the bulk of the diet of chicks: 94% in terms of frequency, 71% in terms of mass. Orthopterans were dominant, especially in terms of biomass (22% by frequency, 58% by mass), whilst Dipterans were well represented in numbers (59% by frequency). Vertebrates, despite their lesser frequency (3%), contributed 23% by mass of the diet. In 2006, 441 prey items were identified. The contribution of insects decreased to 79% by frequency and 15% by mass (mostly Orthopterans) but vertebrates made up a higher frequency: 20% of prey items and 85% by mass of the diet. The availability of prey items was not correlated to their occurrence in the diet, suggesting that the Cattle Egret is a selective predator, with adults selecting prey species for their chicks. A drought in the spring of 2006 increased the availability of fish and lizards to the Cattle Egrets.