ISSN:0158-4197    

DOI:10.1071/MU9910261

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

SummaryThe distribution of breeding colonies of Little PenguinsEudyptula minoron Phillip Island has diminished substantially in the past 90 years and breeding birds are now virtually restricted to the Summerland Peninsula. Declines were found in the numbers crossing Summerland Beach between 1977 and 1988, the number of birds breeding in the principal study area on the eastern boundary of the colony between 1968 and 1988 and the number of active burrows counted in the Parade area between 1980 and 1987. The extent of philopatry, emigration and immigration, changes in breeding success and survival of immatures and adults were investigated as possible factors reducing population size. The relative importance of adult and immature mortalities and breeding productivity to population levels was estimated and adult mortality was found to be far more significant. It is suggested that most immature and adult Little Penguins die at sea. Causes of mortality at sea and on land are reviewed together with population trends of this species elsewhere and compared to those of other species of temperate penguins.

ISSN:0158-4197    

DOI:10.1071/MU9910263

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

SummaryCauses of death of Little PenguinsEudyptula minorfound dead at Phillip Island and other coastal areas of Victoria between 1983–1987 were determined by post-mortem examination. Adults from breeding colonies were generally in good nutritional condition and had no major parasitism or other disease: deaths were mainly due to trauma from predation or road traffic. Post-fledging birds often had substantial parasite infections that resulted in debilitation and death. Most juvenile mortalities occurred on the coast of western Victoria, sometimes as‘wrecks’of considerable numbers of birds that, in the survey period, seemed to be an annual event. The liver flukeMawsonotrema eudyptulaeappeared to be the most pathogenic of the parasites; renal and/or intestinal coccidiosis, intestinal cestodiasis and gastric ulceration associated with ascarid helminthiasis (Contracaecumsp.) were alternative or supplementary problems in some birds. In late winter/spring 1984 and 1985, adult Little Penguins in Port Phillip Bay died of starvation, apparently directly resulting from food deprivation. Affected birds had no major parasitic burdens or other disease that may have influenced their ability to forage. Miscellaneous causes of death included entanglement in discarded fishing tackle and/or plastic debris, the toxic effects of oil in birds contaminated by marine spills and chronic lead poisoning (due to ingestion of part of a lead fishing sinker).

ISSN:0158-4197    

DOI:10.1071/MU9910273

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

SummaryBetween 1967 and 1988, almost 16 000 young and adult Little Penguins were banded on Phillip Island; 413 of these have been recovered away from the Island. Most first-year and adult birds were recovered west (95.3% and 92.6% respectively) of the colony. Significant concentrations of first-year recoveries came from between Phillip Island and Cape Otway in Victoria and from between Warrnambool, Victoria, and Port MacDonnell, South Australia. Few birds have been recovered in their second year away from Phillip Island. The distributional pattern of recoveries of second-year birds was intermediate between that of the first-year birds and adults. Two noticeable differences between the distributions of adults and first-year birds were: the much greater importance of Port Phillip Bay for the older birds (64.8% of recoveries compared to 4.3%) and the less widespread range of adult recoveries. Most first-year mortality at sea occurred between summer and winter whereas adult mortality increased in autumn and early spring. Possible reasons for these differences are discussed.

ISSN:0158-4197    

DOI:10.1071/MU9910278

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

SummaryTransects were run within Port Phillip Bay and off southern Phillip Island, Victoria, between February 1986 and November 1988 and Little PenguinsEudyptula minorcounted. Details are given for group sizes and activities, and totals are considered in relation to the breeding cycle at Phillip Island. Numbers within Port Phillip Bay peaked between June and September, and in May and August off Phillip Island. Little Penguin totals within Port Phillip were negatively and significantly correlated with the number of birds coming ashore at Phillip Island, and with breeding indices there. Counts off the Island did not show such relationships. It is concluded that Little Penguins from Phillip Island complete their breeding, then moult, before moving into Port Phillip Bay. Most Little Penguins in Port Phillip Bay were seen in the eastern and northern areas sampled. This distribution, which complements that shown by banding and radio-tracking, may be related to availability of potential food species. Little Penguins may move into Port Phillip Bay when fish, particularly post-larval fish, are most abundant. Although food shortages have not caused major mortalities, increased commercial fishing has the potential to create problems. There is a need to monitor such harvests and to obtain better information on the populations of prey species.

ISSN:0158-4197    

DOI:10.1071/MU9910287

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

SummaryThe travels at sea, and by implication the foraging ranges, of Little PenguinsEudyptula minorfrom Phillip Island, Victoria, were examined within a period of 18 months in the first seasonal radiotelemetric study of penguins at sea. Two typical travelling patterns are evident: short—term, localised trips of a single day's duration; and long—term trips of several or many days duration and up to many hundreds of kilometres away from the burrow site. Each Little Penguin was capable of both kinds of trip; short-term trips were typical during the breeding season and long-term trips typical during the non-breeding season. Birds undertaking long-term trips generally had lower body masses than birds doing short-term trips. Port Phillip Bay was a favoured destination for long-term trips during winter. In other seasons, long-term trips elsewhere of up to 710 kilometres away from the burrow were recorded. On short-term trips, the mean maximum radius of travel was 7.9 km from the burrow and 95% of the recorded penguin-time was within a radius of 15 km of the burrow and 9 km of the coast. When prey was scarce Little Penguins appeared to range further on short-term trips. The mean net travelling speed on short-term trips was 1.5 km.h−1(range 0–6.9 km.h−1, measured over 0.5 h intervals), and 0.7 km.h−1on long-term trips (range 0.01–3.3 km.h−1measured over 21–126 h), although one penguin travelled at least 113 km in 34.5 h. On long-term trips, in the open sea of Bass Strait, about 74% of the records of telemetered Little Penguins were within 20 km of the coast. For the benefit of wildlife managers, I predict three zones that should contain most of the activity of Little Penguins from southern Phillip Island, including birds from the internationally known‘Penguin Parade’.

ISSN:0158-4197    

DOI:10.1071/MU9910302

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

SummaryThe food of Little PenguinsEudyptula minorwas determined at three sites in Victoria over a 28-month period, covering two complete breeding seasons between 1985 and 1988. There were marked differences between sites in the species taken but most were mid-water shoaling fish and squid under 12 cm in length. There were also changes during the year and from year to year. Two methods of estimating the contribution of different fish to the diet are compared. At one of the sites Little Penguin food was sampled in parallel with another study involving mid-water trawls for small fish. This confirmed that the species taken by the birds were the most abundant present. The breeding of the birds was also monitored at the three sites and was less successful in the second season when less food was being brought ashore by the penguins and collected by the trawls.

ISSN:0158-4197    

DOI:10.1071/MU9910318

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

SummaryThe abundance of PilchardsSardinops neopilchardusand Australian AnchoviesEngraulis australis, the two main prey species of the Little PenguinEudyptula minorat Phillip Island was estimated each month from mid-water and demersal trawl samples taken during the 1986–87 and 1987–88 Little Penguin breeding seasons. During the 1986–87 season, catch rates for Pilchard and Australian Anchovy were highest in October 1986 and next highest in February 1987. During the 1987–88 season, both were not caught until February 1988. The two species were widely distributed during October 1986 but were confined to a small area about 6 km south of the island during February 1987 and 1988. Sea surface temperatures were consistently higher during the second season when catch rates were lower. A total of 61 teleost and cephalopod species were caught during the study, but only four species were caught solely by midwater trawling. The decreased abundance of Pilchards and Australian Anchovies during the second season was reflected in the Little Penguin's diet, increased foraging range and reduced breeding success.

ISSN:0158-4197    

DOI:10.1071/MU9910342

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

SummaryBetween 29 and 47% of the interannual variability in the weight and breeding success of the Little PenguinEudyptula minoron Phillip Island, south-eastern Australia, was attributed, by correlation analysis, to monthly and interannual decreases in the east-west sea temperature gradient across Bass Strait. A station to the east, influenced by the East Australian Current, was generally about 2°C warmer than a station near the colony but these temperatures decreased, especially to the east, with the arrival of west winds. The correlations between physical and biological variables were consistent with the hypothesis that winds from the west bring cooler waters into and across Bass Strait, and that those cooler waters have slightly higher concentrations of nutrients or chlorophyll or more of the fish on which Little Penguins feed. The birds' biological response was measurable on a time scale of months: a decreased sea temperature gradient was associated with increased weights of adults four months later and a July-August decrease in sea temperature gradient was associated with an early start to egg laying in September-October.

ISSN:0158-4197    

DOI:10.1071/MU9910355

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

SummaryIn autumn 1986 about 2000 Little PenguinsEudyptula minorwere found dead along tidelines in western Victoria. Some of these birds came from Phillip Island and all recoveries of banded penguins were made within six months of fledging. Those examined died from starvation exacerbated by parasites; they had enlarged livers (some had haemorrhaged) and trematode, nematode and cestode burdens were high. This wreck is compared with data on other mortalities in the area and with the incidence of birds brought to the Melbourne Zoological Gardens. Meteorological events preceding and following the wreck are noted. It is concluded that waters off western Victoria support large numbers of Little Penguins in autumn and winter (predominantly birds of the year), and that concentrated mortalities occur periodically. Annual variations in the incidence of parasites and their effect may be related to food (= host) abundance and or availability; their influence may be intensified in periods of storms. The number of birds involved in such wrecks is small in proportion to that produced annually in the Bass Strait region. However, even though those which become beach-washed do not represent the number dying, their local concentration may give rise to concern.

ISSN:0158-4197    

DOI:10.1071/MU9910369

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor