Cattle egrets ardea ibis use human-made habitat in a newly colonised area in northern Algeria
Résumé
The Cattle Egret Ardea ibis is a species of Indo-African origin (Kushlan and Hafner 2000) whose biological plasticity is certainly one of the key causes of its worldwide expansion (Franchimont 1986a, Hancock and Kushlan 2005), making it a good model species with which to study the factors that allow colonisation of new environments by invasive birds. We studied the use of natural and human-made feeding habitats by Cattle Egrets in a newly colonised area in the Soummam Kabylie region (36°43'N, 05°04'E), northern Algeria, where the species has bred since 1993, to better understand the relationships between habitat features and the distribution of populations during the entire biological cycle. Until the nineteenth century, the species was breeding in localised areas in northern Algeria (Heim de Balsac and Mayaud 1962). More recently, it started breeding and wintering in a much larger area (Isenmann and Moali 2000, Si Bachir et al. 2008), including semiarid and arid areas in the Sahara (Siegfried 1971, Hancock and Kushlan 2005). Assuming that in North Africa artificial habitats such as crops and orchards are more stable and resource-rich environments than natural habitats (Boukhemza et al. 2000, Kushlan and Hafner 2000, Hancock and Kushlan 2005), we hypothesised that man-made agroecosystems promote the expansion of the species in the recently colonised subhumid and semiarid regions.
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