Spacing and chasing in breeding ducks

Abstract

The behaviour of breeding ducks is described in terms of the relationship of the pair to its home range and the responses of pairs to one another. There are specific, sex, and seasonal variations in the characteristics of the home range. Interactions between pairs involve five types of response: displays, attack, escape and avoidance, sexual pursuit, sociability. Chasing activities of paired males can be hostile or sexual in nature, the latter involving attempts to rape strange females. The characteristics of aerial pursuits ('three-bird flights' and 'attempted rape flights') of Anas species are believed to be determined by variations in the pursuing male's tendencies to (a) stay with or near his mate, (b) attack other males, (c) rape strange females. Male hostility is associated with the existence of a strong pair-bond; raping is associated with a weak bond. A typical 'three-bird flight' results from conflict between the pursuing male's tendency to chase the female of a strange pair (with intent to rape and/or possibly attack her) and his tendency to remain near his mate. Parts of the home range of each pair are shared with other pairs. Where a shared resource is localised in distribution, such as an island suitable for nesting, pairs tend to aggregate. Colonial nesting develops as a result of strong horning tendency in adult and young females, and high productivity in an area with light predation. The behaviour of a number of species appears to be adapted to the various types of resource-sharing required in different habitats. Chasing activities - both hostile and sexual in nature - are believed to bring about dispersion of various types. In a species with a small home range, a high level of hostility, and a strong pair-bond (e.g. Shoveler), a pattern close to classical 'territorialism' is apparent. In more mobile species, there is much overlapping of ranges and the degree of dispersion of pairs (and resulting dispersion of nests) can vary considerably with local conditions. The primary function of chasing and the spacing resulting from it is thought to be the dispersion of nests as au and-predator mechanism.