Three-bird flights in the Mallard

Abstract

Nesting-period flights were investigated in an intensive study completed in 1962. In North Kent, three-bird flights performed during the nesting season are not territorial in the Mallard or the Shoveler. Experiments with a live bird and with models demonstrated the absence of territorial aggressiveness on the breeding grounds. Females were always the centre of attacks and in the Mallard paired males showed remarkable passivity which contrasted with vigorous defence of the female in the Shoveler. Two distinct levels of intensity were discovered in the three-bird flights which are considered to be a phase in the indiscriminate pursuit of females characteristic of Anas species: comparable behaviour in the Shoveler is described. Three-bird flights coincide with maximum activity in the gonad cycle and with the period of isolation of drakes. Behaviour of paired drakes during Mallard flights indicates a polygamous tendency. It is suggested that the flights are primarily sexual in origin, but that latent gregariousness is also a causal factor. The biological significance is obscure, but possible explanations are given.