Ecological correlates of breeding success of Western Cattle Egret Ardea ibis in northeastern Algeria

Abstract

We investigated the relationships between habitat characteristics, interspecific interactions, and breeding success of the Western Cattle Egret Ardea ibis in Numidia, northeastern Algeria, from 2003 to 2007. We hypothesised that (1) habitat and site characteristics significantly affect nesting parameters, and (2) habitat quality, nesting parameters and breeding phenology impact reproductive outcomes. To test these, we monitored breeding phenology, nest site selection, and reproductive success across diverse habitats. Our findings revealed that nesting height varied according to the vegetation type used as nesting support. Egg-laying occurred between 22 April and 26 July, with clutch sizes averaging 3.4 eggs. Reproductive parameters varied significantly by site and year, with the highest success at Lake Fetzara, a high-quality natural marsh. Clutch size and hatching success declined seasonally, supporting the hypothesis that age and/or body condition of breeders might influence reproductive performance. Reproductive success was not associated with nest characteristics (nest height, diameter) but was positively associated with habitat quality. In addition, breeding performance was negatively correlated with laying date and positively correlated with clutch size, indicating seasonal resource constraints but weak brood reduction selection. We also documented higher reproductive losses due to ectoparasites, adverse weather and human disturbance, confirming the adverse effects of both density-dependent and density-independent factors. Notably, infrequent brood parasitism of Squacco Herons Ardeola ralloides and Little Egret Egretta garzetta nests by Western Cattle Egrets suggests complex interspecific interactions that might influence reproductive strategies.