Publications Archive

In a 1-day study of the Australian Coot (Fulica atra australis), the duration of dives increased with increasing depth, although the frequency of diving remained relatively constant. Duration and frequency of dives at given depths appeared not to vary with age. However, aggressive adults often drove young birds into deeper water. The duration of dives changed with the time of day, the birds preferring to dive in direct sunlight.

In 1991, 4780 km of coast of New Zealand were patrolled and 6955 dead seabirds were found as pan of the Beach Patrol Scheme. An unusual find was a Red-tailed Tropicbird (Phaethon rubricauda), and more than usual were found of the Antarctic Petrel (Thalassoica antarctica), White-headed Petrel (Pterodroma lessonii), Little Black Shag (Phalacrocorax sulcirostris) and Brown Skua (Catharacta skua lonnbergi). A summary is given of the coastal and monthly distributions of Morus and Sula species found during the 1943-1991 period. Overall, 5637 Australasian Gannets (Morus serrator) were found, mainly on beaches of the northern half of the North Island. The peak period of adult recoveries was in December-February, but that of juveniles was in February-May. Both the Brown Booby (Sula leucogaster) and the Masked Booby (Sula dactylatra) are vagrants to the New Zealand mainland, with four and one individuals respectively having been found by patrollers.

G.R. Gray first used the name Pelecanus serrator in association with the drawing by Sydney Parkinson of an adult Australasian Gannet taken at sea near the Three Kings Islands in 1769. Parkinson’s drawing is an illustration of the specimen described in manuscript by Daniel Solander as Pelecanus serrator. Both the drawing and the description are of the type specimen and have previously unrecognised taxonomic importance. The correct type locality of Morus serrator is the vicinity of the Three Kings Islands.

The Kakerori, or Rarotonga Flycatcher, of the Cook Islands has two distinctive colour forms: orange and grey. Our colour-band study showed that colour is simply related to age, not to sex as described earlier. When fledglings leave the nest their body is covered in grey down, and their wings and tail are still growing. Orange juvenal plumage is attained about one month after fledging. Despite having similar orange plumage, yearlings can be distinguished from 2 year-old birds on the basis of bill colour and wing and tail lengths. Third-year birds have elements of both main colour phases. Once the definitive basic plumage is attained in the fourth year, the age of grey birds cannot be determined. Wing and tail lengths apparently increase at each successive moult until the definitive basic plumage is reached. Males are larger than females, with bill length being the best discriminator. The progressive colour change recorded here parallels that described for three of the four other species of Pomarea flycatcher in eastern Polynesia, but colour variation in the other species, and in some other monarch flycatchers in the Pacific, needs critical examination. The ability to distinguish three cohorts of Kakerori is useful in measuring annual variations in productivity, survivorship, and age structure of the population.

Monthly bird counts were recorded for Kaikorai Estuary, Otago from July 1989 to June 1991. Fifty species were noted, including passerines on the estuarine fringe. The predominant species was the Southern Black-backed Gull (Larus dominicanus), which accounted for 61% of the birds surveyed. They overwhelmed the Dunedin City Council refuse up site at Green Island and, to a lesser extent, a tip in private use. Mallards (Anas platyrhynchos) and Starlings (Sternus vulgaris) were the next most common species. Numbers of birds decreased with distance from the tip sites but, conversely, the number of species increased. Numbers were highest in March-April, but declined rapidly by two-thirds to a July-August low. This decline was due to the dramatic fall in duck numbers with the opening of duckshooting season and to the onset of winter. The total annual count for the second half of the survey (July 1990 to July 1991) was 4% down on the previous 12 months, but this was not statistically significant.

Between 1988 and 1992, we conducted the first comprehensive survey of the number and breeding distribution of the New Zealand Dotterel (Charadrius obscurus) on Stewart Island. The population forms three post- breeding flocks, two of them on Stewart Island; band sightings have confirmed an earlier suggestion that the flock at Awarua Bay, Southland, is also composed of birds from the island. The population is widely spread over difficult terrain during the breeding season; autumn counts of the flocks provide the only practical means of assessing population size. Comparisons with earlier counts show that the population has declined to about one-fifth of its former size in the past 37 years The population is critically endangered because the decline continues and only 60-65 dotterels remain. Average annual mortality of banded adults between 1990 and 1992 was 23%. The major reason for the decline is believed to be predation by feral cats. Band sightings suggest that, apart from Southland, most or all of the recent NZ Dotterel records from the South Island coast (including Farewell Spit) are of juveniles wandering from Stewart Island.

A survey of birds in six Northland forests in 1979 was repeated in 1993, primarily to test whether numbers of New Zealand Pigeon had changed significantly. Counts of Eastern Rosella, Grey Warbler, Fantail and Tui had changed little. Counts of New Zealand Pigeon and Silvereye were significantly lower in 1993 and those of New Zealand Pigeon are thought to reflect long- term changes in abundance. Kaka and Kokako were each recorded in only one forest in 1993 compared with four and three forests respectively in the first survey. Pied Tit and Myna had significantly higher counts in 1993 than in 1979.