摘要:

SummarySeabirds were counted on Michaelmas Cay every month from May 1984 to April 1990. Seven species bred during the study. The major breeding species were Sooty TernSterna fuscata, Common NoddyAnous stolidus, Crested TernS. bergiiand Lesser Crested TernS. bengalensis.Silver GullLarus novaehollandiae, Black-naped TernS. Sumatranaand Bridled TernS. anathaetusbred in some years in small numbers. Sooty Terns had a sub-annual breeding cycle of 8.6 months duration, measured between peaks of breeding numbers, while the other species were annual breeders, five in summer and one (Silver Gull) in winter. In successive breeding cycles, the sizes of breeding populations of Sooty Tern and Common Noddy both fluctuated strongly. Crested Tern numbers increased slightly then decreased, and Lesser Crested Tern numbers increased strongly then decreased again. Average Silver Gull numbers remained fairly stable over the study period. Fledging success varied considerably among breeding cycles of Sooty Tern, Common Noddy and Crested Tern. Lesser Crested Terns bred successfully in three cycles and showed increasing fledging success over the study period. Climate had a major influence on breeding populations of Sooty Tern and Common Noddy. Three cyclones were recorded; one altered the periodicity of Sooty Tern breeding cycles and two affected its breeding numbers and success. In mid-year, prolonged periods of strong winds caused breeding failures in Sooty Tern and Common Noddy. Erosion of the cay also caused nest losses. Human disturbance had little effect on breeding populations.

ISSN:0158-4197    

DOI:10.1071/MU9920001

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

SummaryMale bowerbirds build and decorate bowers to attract females as copulation partners. Here we report the first information on the relationship between the bower and mating patterns in the Spotted BowerbirdChlamydera maculata.The mating success of male Spotted Bowerbirds is correlated with the quality of male bowers and several measures of bower decoration. Bower destruction and decoration stealing are rare. The low rate of interaction among bower holders appears to result from the large distances between bowers. Studies of the Satin BowerbirdPtilonorhynchus violaceushave shown a much higher level of stealing and destruction and support the view that male interactions are critical in determining the level of bower decoration and bower quality (Borgia 1985b; Borgia&Gore 1986). The low levels of stealing and destruction in Spotted Bowerbirds, coupled with the correlation of bower quality and mating success, suggest that high levels of male interaction are not a necessary prerequisite for females to use bowers as a factor influencing mate choice. We consider the implications of this finding in regard to the evolution of bower building and the evolution of sexual display.

ISSN:0158-4197    

DOI:10.1071/MU9920011

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

SummaryObservations of individually marked Western Long-billed CorellasCacatua pastinatorin a breeding area at Burakin in the central wheatbelt of Western Australia indicated that there were three phases of movement patterns. The juvenile phase started with fledging; the young and their parents moved to an area with food, water and shelter in close proximity where they were joined by other family groups and immature birds. Two to three weeks later, the families and immature birds moved to Dalwallinu, 55 km to the north-west, where they joined up with birds from other breeding districts, returning to the breeding districts between January and March. The immature phase from independence at three to four months lasted until the birds started breeding; immatures returned to Dalwallinu each summer and spent the rest of the year in a breeding district as part of a locally nomadic flock that moved over an area of about 250 km2; some dispersal to breeding areas other than their natal area may occur during this phase. The adult phase included the annual movements with offspring (if any) to Dalwallinu and back. For the rest of the year, the nest area was the focal point of a pair's activities. Foraging distance of breeding birds declined during the winter and was at a minimum when they were incubating and feeding nestlings. Breeding adults were strongly philopatric and strongly bonded so that except when incubating or feeding, the partners of a pair were rarely separated. The summer movement to a common feeding area was observed also in two other populations and its origins are discussed. Comparisons with the movements of other cockatoos in the wheatbelt are made.

ISSN:0158-4197    

DOI:10.1071/MU9920019

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

SummaryThe Magpie GooseAnseranas semipalmatashows substantial sexual dimorphism in body size, with males being 34% heavier. In at least one habitat (homogeneous sedge swamps) this dimorphism appears to be associated with slight divergence in foraging niche. The size distribution ofEleocharis dulcistubers ingested by Magpie Geese is similar to their availability in swamp sediments, but there are substantial differences between sexes and suggestions of variation between age groups. Males take more of the larger tubers than females, and juvenile (first-year) birds may ingest a greater proportion of small tubers than birds more than one year old. We suggest that this divergence arises through a mix of size, social and behavioural factors. Within family groups larger males may gain prior access to undisturbed foraging sites, and be better able to exploit cues to tuber size that may be associated with deeper-rooted larger plants. Juveniles accustomed to foraging for seeds in breeding areas may be slow to adopt their parents' foraging strategies after moving to dry season habitat.

ISSN:0158-4197    

DOI:10.1071/MU9920028

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

SummaryA capture-recapture study of Gouldian FinchErythrura gouldiae, Masked FinchPoephila personataand Long-tailed FinchP. acuticaudaat two sites in the Northern Territory (extending over 22–24 months) showed a disappearance of banded Gouldian Finches from populations at both study sites. The lack of recaptures of banded Gouldian Finches is due either to much higher mortality or to greater rates of emigration, or to both, relative to Masked and Long-tailed Finches. Some evidence is presented for each explanation but the data do not adequately discriminate the alternatives (or define the relative contributions of both).

ISSN:0158-4197    

DOI:10.1071/MU9920033

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

ISSN:0158-4197    

DOI:10.1071/MU9920038a

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

SummaryThe White-throated GrasswrenAmytornis woodwardiis endemic to the sandstone plateaux and escarpments of western Arnhem Land and surrounding areas of the Northern Territory. Recent surveys extend the known range 100 km east and 80 km south. This grasswren appears to be neither rare nor endangered. Based on estimates of the area of suitable habitat, its total population is probably over 14 000, possibly over 50 000. Optimum habitat appeared to be flat, often sparsely vegetated, high plateaux; heavily dissected escarpments and outliers supported less dense populations. The most consistent components of the habitat were bare rock and spinifex, which together constituted almost three-quarters of the sub-stratum. Fire is important in the ecology of the species but information at present is inconclusive as to its effects. Regular burning may indirectly benefit these birds by maintaining a high density of spinifex and low density of more fire-sensitive plant species. The diet ofA. woodwardiis not specialised, and includes plant stems, seeds and insects. The breeding season is long (December to May or June) and allows two or more broods to be produced. Territories averaging 10 ha were held by pairs and larger groups during the breeding season, providing evidence of cooperative breeding.

ISSN:0158-4197    

DOI:10.1071/MU9920039

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

ISSN:0158-4197    

DOI:10.1071/MU9920052

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

ISSN:0158-4197    

DOI:10.1071/MU9920057

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

ISSN:0158-4197    

DOI:10.1071/MU9920061

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor