摘要:

SUMMARYWoodall, P.F. 1984. Kleptoparasitism in Hardheads and Pacific Black Ducks, including size-related differences. Emu 84: 65–70.HardheadsAythya australis, diving for freshwater mussels in a lake on the Queensland University campus, were chased by other Hardheads and by Pacific Black DucksAnas superciliosa.Only Pacific Black Ducks and male Hardheads were successful pirates (9.8% of chases), fewer female Hardheads were pirates and they were never successful. More female Hardhead hosts than males dived during a chase and females lost fewer mussels to Pacific Black Ducks than did males. There was no simple relationship between the numbers of pirates and the probability of successful piracy in a chase. During the period of observation, there was a decline in the median time of chases, particularly of female Hardheads, and also a decline in successful piracy (20 to 5%). It is suggested that male and female (= smaller) Hardheads may form an Evolutionarily Stable Strategy of divers and pirates.

ISSN:0158-4197    

DOI:10.1071/MU9840065

出版商:Taylor&Francis    

年代:1984

数据来源: Taylor

摘要:

SUMMARYSERVENTY, D.L. and P.J. CURRY 1984. Observations on colony size, breeding success, recruitment and inter-colony dispersal in a Tasmanian colony of Short-tailed ShearwatersPuffinus tenuirostrisover a 30-year period. Emu 84: 71–79.A programme to mark a small colony of Short-tailed Shearwaters, by means of monel leg-bands, was begun on Fisher Island during 1947–50 as part of a comprehensive study. Banding of all adults and their young has continued every year since (to 1980).The number of breeding burrows occupied each year declined steadily during the first 25 years of the study, at the end of which numbers had been reduced by 71%. More recently, numbers have begun to increase again. No change has occurred in the relative sizes of three sub-colonies existing within the island. Annual rates of breeding success were usually lower than those reported from other less-studied colonies and have tended to be either relatively high (>55%) or else poor (<40%). Some chicks were raised every year; on average, the smallest sub-colony was as successful as the largest.Nearly all breeding failures occurred before the chick-rearing stage and few successfully hatched chicks failed to fledge. No banded young were recaptured at the colony before age two and most not until three years and upwards. Age at first breeding for both sexes ranged from five to at least ten years. Forty-one per cent of chicks banded over 20 consecutive seasons were subsequently recovered alive on their natal island but only 35% of these were recruited as breeders. Losses of immatures and young adults through emigration were offset by an annual recruitment of unbanded immigrants, most of which could not have been bred on the island. After 30 years, the proportion of Fisher- bred breeders in the colony was stable at 41–46%. Band recoveries confirmed inter-colony dispersal by young adults. Fisher-bred birds found in nearby colonies were encountered mainly in the nearest breeding area on the closest neighbouring island.Repeated disturbance of the colony during the course of the study is thought to have contributed to the decline of the colony, due to increased burrow desertion, decreased breeding success and decreased recruitment of young adults.

ISSN:0158-4197    

DOI:10.1071/MU9840071

出版商:Taylor&Francis    

年代:1984

数据来源: Taylor

摘要:

SUMMARYWOINARSKI, J.C.Z. 1984. Interbreeding of the Spotted and Yellow-rumped PardalotesPardolotus punctatusandP. xanthopygus.Emu 84: 80–86.Two species of spotted pardalotes are currently recognized,Pardalotus punctatusof mesic areas andP. xanthopygusof more xeric areas. Morphologically and ecologically, the two are extremely similar but lack of evidence of interbreeding has led to reluctance to lump the two taxa. This study examines breeding in a contact area near Bendigo, Victoria. Of seven pairs in a study area of forty ha, only two appeared to comprise individuals of the same taxon. Territories did not overlap and were defended vigorously; all males approached and attacked recorded calls and freeze-dried models of malepunctatusandxanthopyguswithout apparent discrimination. In some individuals in this area display calls and plumages were intermediate betweenpunctatusandxanthopygus.This study suggests the two taxa are not behaving as distinct species in this area of contact. Reports on intergradation from other areas in south-eastern Australia further question the validity of specific separation ofP. xanthopygusandP. punctatus.

ISSN:0158-4197    

DOI:10.1071/MU9840080

出版商:Taylor&Francis    

年代:1984

数据来源: Taylor

摘要:

SUMMARYDEBUS, S.J.S. 1984. Biology of the Little Eagle on the Northern Tablelands of New South Wales. Emu 84: 87–92.The diet and breeding biology of the Little EagleHieraaetus morphnoideswere investigated at Armidale, New South Wales in 1980. Data were supplemented by the RAOU Nest Record Scheme. Little Eagles took a wide range of vertebrate prey species in the breeding season. Prey items recorded at three nests consisted, by number, of about 60% mammal, 25% bird and 15% lizard and these figures agreed closely with the percentage occurrence of these prey types in pellets (c.55% mammal, 25% bird and 20% lizard). Active nests were in living trees in patches of woodland. The ratio of two-to single-egg clutches was about 2:1. The incubation period was 36 to 40 days, and males shared incubation. The nestling period was about nine weeks, and the post-fledging dependence period appeared to last at least six weeks. The breeding cycle occupied about four months from nest building to fledging, and, for the district, about five months (August-January). Fledging success was about 0.5 young per pair per year, and about one in six successful nests raised two young. Breeding density was at least one pair per 1600 ha. Prey taken from each home range in the six-month breeding season was estimated at 120 young lagomorphs (48 kg), 50 birds (3 kg) and 30 lizards (4 kg).

ISSN:0158-4197    

DOI:10.1071/MU9840087

出版商:Taylor&Francis    

年代:1984

数据来源: Taylor

摘要:

SUMMARYDAWSON, T.J., D. READ, E.M. RUSSELL and R.M. HERD. 1984. Seasonal variation in daily activity patterns, water relations and diet of Emus. Emu 84: 93–102.The pattern of activity of EmusDromaius novaehollandiaein western New South Wales has been examined and contrasted with that of the other large native animals in the area, Red KangaroosMegaleia rufaand EurosMacropus robustus.A detailed behavioural analysis indicated that Emus were diurnal and spent a large part of the day feeding in both summer and winter. During hot days in summer they occasionally sheltered among trees from the radiation heat load. The water requirements of adult Emus measured by tritiated water turnover do not appear high but intake may be limited by the size of the simple gut, resulting in a relatively high frequency of drinking, once per day and occasionally twice per day during hot summer conditions. The water use of chicks, especially young chicks, was much greater than that of the adults. Water losses from an incubating bird, however, were one fifth of those of adult birds in similar conditions. The Emus were omnivorous, relying on insects, seed heads, berries and succulent vegetation. The Emus successfully make their living in the arid zone very differently from the marsupials and the basis of this is discussed in relation to recent findings about their physiological adaptations.

ISSN:0158-4197    

DOI:10.1071/MU9840093

出版商:Taylor&Francis    

年代:1984

数据来源: Taylor

摘要:

SUMMARYROBERTSON, H.A. and M.D. DENNISON. 1984. Sexual dimorphism of the Chatham Island WarblerGerygone albofrontata.Emu 84: 103–107.Evidence that the Chatham Island Warbler is sexually dimorphic in plumage and size is presented from field observations on breeding pairs on three islands in the Chatham Group, New Zealand, over five breeding seasons; and from an examination of museum skins. Descriptions, measurements, and distinguishing field and behavioural characteristics of adult males and females, and juveniles are given. It is suggested thatG. albofrontatais not a derivative ofG. igata, but the result of an earlier invasion by a warbler that has since become extinct on the New Zealand mainland.

ISSN:0158-4197    

DOI:10.1071/MU9840103

出版商:Taylor&Francis    

年代:1984

数据来源: Taylor

ISSN:0158-4197    

DOI:10.1071/MU9840108

出版商:Taylor&Francis    

年代:1984

数据来源: Taylor

ISSN:0158-4197    

DOI:10.1071/MU9840111

出版商:Taylor&Francis    

年代:1984

数据来源: Taylor

ISSN:0158-4197    

DOI:10.1071/MU9840113

出版商:Taylor&Francis    

年代:1984

数据来源: Taylor

ISSN:0158-4197    

DOI:10.1071/MU9840116

出版商:Taylor&Francis    

年代:1984

数据来源: Taylor