Behaviour of the cattle egret Ardeola ibis
Ardeola ibis (.L.) is a small white heron, generally considered to be one of the most terrestrial members of its semi-aquatic family. It is a highly successful species, both in terms of numbers and of geographic range. Apart from man and his commensals, it is probably the commonest of the six terrestrial vertebrates with cosmopolitan breeding ranges, the other five all being bird species too (Voous 1960). A. ibis is gregarious, roosting and nesting in very large numbers, so one aim of this study is to investigate advantages of and adaptations to a social way of life, and to see whether the species' success is in any way a result of its gregariousness. Several taxonomic reviews, notably those of Lorenz (1941) and Johnsgard (1961) on Anatidae, have been based on behavioural characters, because many behaviour patterns are as conservative and species-constant as structural features are. For this reason, and because adequate behavioural studies have to date been carried out on only about 7 of the 64 Ardeid species, the work was extended to include two other species, Egretta garzetta and E. intermedia. The present study is also designed to provide material for a projected review of the Ardeidae (Curry-Lindahl pers. comm.).
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