Aspects of the breeding biology of New Zealand scaup (Aythya novaeseelandiae)

Type of content
Theses / Dissertations
Publisher's DOI/URI
Thesis discipline
Zoology
Degree name
Master of Science
Publisher
Journal Title
Journal ISSN
Volume Title
Language
English
Date
1991
Authors
Stokes, Sarah J.
Abstract

The endemic scaup, Aythya novaeseelandiae, is New Zealand's only surviving true diving duck. Distribution is throughout the country but, as a consequence of habitat loss, scaup are now mainly restricted to the freshwater lakes and lagoons in the north and east of the North Island, and to the high country lakes of the South Island. Current knowledge concerning wild scaup populations is extremely limited, particularly with respect to their breeding biology, their population size and their ecology. Research into the breeding biology of an island nesting population was undertaken at Lake Clearwater, a high country lake situated approximately 150 km southwest of Christchurch. Investigations into the breeding attributes and nesting success for this population were made over two breeding seasons: 1989/90 and 1990/91. In the 1989/90 season, breeding commenced in October with peak hatching occurring within the months of November and December, although nesting does occur as late as February. During the second breeding season nesting occurred six to eight weeks later, but all breeding was finished by the middle of January. An average of eight eggs per clutch were laid, an egg being laid about once every 29 hours, with incubation taking 29 to 31 days. Each egg laid constitutes about 12% of a female's body weight, and females typically lay equivalent to their own weight in eggs. Hatching is synchronous and chicks are brooded for up to 24 hours before leaving the nest. Chicks are capable of self-feeding and diving. Once chicks leave the nest, brood amalgamations often occur. Typically, these involve chicks of similar ages and creching occurs for two weeks. The acquisition of food resources and social facilitation between chicks is suggested as the purpose of brood amalgamation. After disbanding from the creches, broods are reared solely by the female (the pair bond is dissolved when incubation begins) and females vigilantly protect their brood from avian predators. Nesting success, calculated as the proportion of nests surviving through to hatching, was 64% in the first season and 26% in the second season. The lower level of nesting success in the second season was partly due to the establishment of a feral cat on the breeding island. Avian predators, notably harriers, Circus approximans, also killed breeding females. In all, 20% of all nesting females were destroyed during the 1990/91 season through the activities of both mammalian and avian predators.

Description
Citation
Keywords
Aythya novaeseelandiae--Reproduction
Ngā upoko tukutuku/Māori subject headings
ANZSRC fields of research
Rights
All Rights Reserved