Observations of Shags made on Heard Island during the 1992-1993 expedition

Published: 2026-10-14

These data have been extracted from the Australian Antarctic Data Centre Biodiversity Database. They comprise of observations made of Heard Island Shags (Phalacrocorax nivalis). They provide dates, locations, nests, and numbers of individuals. The observations were made by the expedition biologist, Ken Green. Also see the related metadata record, "The 1992 Wintering Field Season at Heard Island" to access the full report of that expedition. Below are extracts from the report relating to the work conducted on the Heard Island Shag, beyond the observations that are presented here. These sections of the report were written by Ken Green. Inter-annual and seasonal differences in the diet of the Heard Island Shag Phalacrocorax nivalis. The diet of the neritic-feeding Heard Island Cormorant, Phalacrocorax nivalis, was previously investigated and found to consist mainly of scale worms. This diet, unusual for a cormorant, prompted the re-examination of the diet throughout a full year to investigate the temporal stability in the diet between seasons and between years. Regurgitated casts were collected at Stephenson Lagoon (a major roosting site and latterly a major breeding site), at the eastern end of Heard Island. Individual casts were kept separate and were returned to the laboratory for analysis. Casts were broken open in water in a sieve of 0.5mm mesh and were sorted beneath a dissecting microscope. Fish otoliths were removed for further identification and measurement. Once the segregation of breeding and non-breeding bords was confirmed, collections from the two groups were kept separate. While adults were feeding chicks, regurgitations that spilled onto the ground and were not retrieved by the adults were collected. Breeding biology of the Heard Island Shag Phalacrocorax nivalis. The fact that there has been no full investigation of the breeding biology of this species is due mainly to the difficulty of access to their breeding locations. Only two small breeding colonies were recorded prior to 1959 at Saddle Point and Sydney Cove. The former is on a point of volcanic origin and is surrounded by glaciers which cost the lives of two expeditioners and the latter was on a stack 50m offshore. The Sydney Cove colony moved from the stack to adjacent cliffs on the main island between 1980 and 1985. These were the only breeding sites on the island found in a survey on foot and by helicopter in 1986. The only evidence to suggest that breeding may occur elsewhere on the island came when Vining reported seeing two chicks at Stephenson Roost. The breeding of the Heard Island Shag at Stephenson Roost in 1992 at a time when a wintering expedition was within 200 metres was therefore adventitious and provided the first chance to study a breeding colony almost daily, throughout the whole season. Behavioural observations of a breeding population of the Heard Island Shag The major roosting site of shags at Heard Island, about 200m from the 1992 overwintering base at Spit Bay, was the subject of weekly counts and monthly collections of regurgitated casts. In the course of these counts it became obvious that nesting was going to take place, this being the first known major breeding effort at the eastern end of Heard Island. Advantage was taken of this proximity of these nesting shags to study the signal patterns and to compare them with those documented for other species within the blue-eyed shag complex. Occasional observations were made of the roost until clear evidence that nesting was serious. From this time (late September 1992) frequent periods of observation took place until departure of the expedition from Heard Island. The frequency and intensity of this effort was determined by commitments to other programs which had a higher priority. Visual records of behaviour were obtained using 35mm black and white film and a Canon super 8 video. Behavioural data were recorded in a note book. An attempt was made on different visits to cover all parts of the day to cover any diurnal changes in behaviour.