The Tasmanian native hen, Tribonyx mortierii. I. Patterns of behaviour

Abstract

The repertoire of behaviour of a natural population of Tasmanian native hens was studied for 3 yr (1930 hr of observation). Detailed descriptions of the main activities are given. The native hen cannot fly but walks and runs very efficiently and can reach speeds of 35 m.p.h. It swims well though it is less aquatic than the dusky moorhen. It makes at least 14 calls; sound spectrograms of 12 are given. It uses a variety of characteristic grunts of very low frequency in aggressive, parental, and alarm behaviour. The alarm grunt has properties which make it difficult to locate the bird producing it. A two-syllable aggressive call is antiphonal, one part being produced by the male, the other by the female, in nearly perfect interpolation. Normal alarm reaction to predators consists of 11 elements. In addition, a "small mammal" distraction run and a special alarm call are used only when it has young. Reactions to predators depend both on the behaviour and the species of the predator. Most alarm was shown towards wedge-tailed eagles. Goshawks were differentiated from brown hawks and swamp harriers, and ravens from all three. A well-developed aggressive display is used to defend a permanent territory. This display is partly visual and partly acoustic and consists of seven elements. Adults often fight vigorously, mainly with the legs and bill. The females usually start the precopulatory display. After copulation males adopt a characteristic pose resembling that of the female just before copulation. A meeting display occurs during the breeding season and is thought to act as a means of overcoming incipient aggression between sexual partners. After the eggs hatch an almost unconcealed nest is built in the open, in which the young are brooded at night. The parents feed and tend their chicks closely after hatching, and are sometimes helped by their young of the previous year and even by the previous brood. Efficient response to predators develops early in the chicks. By contrast, most social behaviour starts at a later age and takes much longer to mature fully. The behaviour of the dusky moorhen, particularly its sexual behaviour, has greater similarity to that of the Tasmanian native hen than has the behaviour of the eastern swamphen. This suggests that the Tasmanian native hen is more closely related to the dusky moorhen. Few striking modifications of behaviour seem to have resulted from flightlessness. Probably the most important has been the accentuation of the sedentary way of life of the Tasmanian native hen.