摘要:

SUMMARYHulsman, K. 1977. Breeding success and mortality of terns at One Tree Island. Great Barrier Reef. Emu 77: 49–60.Defence of the nest by Black-naped, Roseate, Lesser Crested and Crested Terns and strategies of predation used by Silver Gulls were studied. Strategies used by Gulls differed as did the rate of success between individuals and only a few were responsible for most predation. Their behaviour was affected by the size of the defender of the eggs or chicks and by the size of an egg. Breeding success and causes of mortality of eggs and chicks of Black-naped, Roseate, Bridled and Crested Terns were determined. Mortality resulted mainly from predation (1.6 to 83.1%), flooding of nesting areas (6.6 to 50.6%) and starvation (<82.4%) caused by a cyclone preventing adults foraging for at least three days. However, the importance of these causes of mortality differed among colonies over three successive breeding seasons. Although the breeding success of Lesser Crested Terns was determined, the main causes of mortality were not. The generalizations that populations are limited by abundance of food or competition for it are discussed. Breeding success of Black-naped and Roseate Terns is too low to maintain the present size of their colonies at One Tree Island. In contrast, the colonies of the Bridled and Crested Terns can be maintained or possibly increased, depending on post-fledging mortality.

ISSN:0158-4197    

DOI:10.1071/MU9770049

出版商:Taylor&Francis    

年代:1977

数据来源: Taylor

摘要:

SUMMARYDiamond, J. M., and A. G. Marshall. 1977. Niche shifts in New Hebridean birds. Emu 77: 61–72.Niche breadth varies with competitive pressure. When most of the pressure experienced by a species is from a single close competitor, its niche tends to be broader in the absence than in the presence of the competitor. When‘diffuse competition’(the combined effects of numerous more distant competitors) is more significant, the niche tends to be broader on islands with few than with many species. We summarize all known examples of such niche shifts for New Hebridean birds, based on comparing conspecific populations on different New Hebridean islands or New Hebridean populations with those in another archipelago. The commonest niche shifts are spatial ones affecting type of habitat, altitude or vertical foraging range. Other shifts affect size and number of islands inhabited: shifts from small to large islands and shifts in‘incidence’. The remaining types of shifts are in diet and in abundance. We conclude that competition is the proximate cause of distributional limits for most New Hebridean species. We hypothesize that rapid behavioural responses of colonists to altered competition mainly affect spatial parameters of niches. Subsequent slower genetic changes modify foraging technique and diet and may produce shifts into forest and montane forest according to so-called taxon cycles. Further work is needed to test directly this proposed sequence of behavioural and genetic changes in colonists and to compare the importance of interspecific aggression and depletion of resources as proximate mechanisms of competitive exclusion.

ISSN:0158-4197    

DOI:10.1071/MU9770061

出版商:Taylor&Francis    

年代:1977

数据来源: Taylor

摘要:

SUMMARYPaton, D. C., and H. A. Ford. 1977. Pollination by birds of native plants in South Australia. Emu 77: 73–85.We present evidence that birds pollinate many native plants. Honeyeaters persistently and often visit flowers and regularly carry pollen. When they probe another flower some pollen is deposited on the stigma, thus effecting pollination. Floral structure or the arrangement of inflorescences ensures that birds probing flowers will regularly brush the anthers and stigmas. The pollen is carried on the bill or feathers and is well suited to its mode of transport. No specific relation between birds and flowers was found. Each species of bird visited many flowers and each species of plant was visited by many species of birds. The plants appear adapted to the Meliphagidae as a whole. However, insects also visited many plants. The importance of birds compared to insects as pollinators is discussed.

ISSN:0158-4197    

DOI:10.1071/MU9770073

出版商:Taylor&Francis    

年代:1977

数据来源: Taylor

ISSN:0158-4197    

DOI:10.1071/MU9770086

出版商:Taylor&Francis    

年代:1977

数据来源: Taylor

ISSN:0158-4197    

DOI:10.1071/MU9770088

出版商:Taylor&Francis    

年代:1977

数据来源: Taylor

ISSN:0158-4197    

DOI:10.1071/MU9770089

出版商:Taylor&Francis    

年代:1977

数据来源: Taylor

ISSN:0158-4197    

DOI:10.1071/MU9770090

出版商:Taylor&Francis    

年代:1977

数据来源: Taylor

ISSN:0158-4197    

DOI:10.1071/MU9770092

出版商:Taylor&Francis    

年代:1977

数据来源: Taylor