摘要:

SummaryWinter survival with respect to dominance classes of 932 individually colour‐ringed Silvereyes was examined on Heron Island, Great Barrier Reef, between 1965 and 1969. The dominants (winning two‐thirds or more of aggressive encounters) had significantly better chances of survival between May and August (southern winter) than other birds. The 1967/68 year group was studied in detail; the young born early in the breeding season contained proportionately more dominants than those born later in the season and dominant birds tended to survive better in winter. Adults in the same period showed no dominance dependent survival. The weight of birds in winter differed between first‐year birds and adults in most cases, but winter mortality within each year‐group was not related to the weight of individual birds in May. However, the dominant class had a smaller proportion of birds losing weight through the winter than other classes, and the dominant adults and the intermediate class of first‐year birds tended to be heavier than others in August. The lengths of wing, tail, tarsus and exposed culmen examined for the 1967/68 year group showed no significant trends in either survival or dominance classes. Better survival of dominant birds is considered to be a consequence of their feeding advantages over others, but the intensity of selection for an ability for dominance may fluctuate from year to year in relation to the population density and distribution and abundance of fo

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1980.tb00899.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SummaryA colony of the Edible‐nest SwiftletAerodramus fuciphagusnesting in a Chinese shophouse in Penang, Peninsular Malaysia, was studied for seven months. Birds bred throughout, but laying was concentrated in the period October to February. Incubation and fledging periods were 23 ± 3 days and 43 + 6 days, respectively. Most young hatched during the dry season. The normal clutch size was two, with many birds laying second clutches (75%) and some third clutches (15‐4%) using the same nest. Clutch size showed no variation with clutch order or month.The overall hatching success was 69‐0 %, most losses caused by eggs falling from or with the nest. Fledging success was similar for broods of two (625%) and broods of one (59‐4%), so that the former were twice as productive. The main loss of chicks occurred when they fell from the nest and were eaten by mammalian predators. There was a tendency for breeding success to decline with successive clutches, but not with month, being highest in November (53‐6 %) and February (55‐6 %).The growth rate of single chicks and successful broods of two was similar, except that the second chick was more prone to fluctuations in weight. Some second chicks showed evidence of starvation before falling from the nest.Diet was examined by analysis of foodballs regurgitated by mist‐netted adults. Foodballs weighed 0–13‐1 08 g and, on average, contained over 500 prey items. The main arthropods caught were Hymenoptera (40‐8%), Ephemeroptera (26‐4%), Homoptera (15‐4%) and Diptera (7‐7%). Flying ants and mayflies contributed most by weight, although figwasps and mayflies were the most numerous prey items.Only in December did the percentage of moulting mist‐netted adult swiftlets fall below 70 %. It appeared that many birds were moulting and breeding simultaneously, although 21%of birds had primaries moulting in two places, suggesting arrested moult.Diurnal activity showed a normal high dawn exodus and dusk inflow of birds, although there was evidence of an increase of birds flying out prior to the dusk inflow. Nest harvesting was continued throughout the study, but most of the marked nests under

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1980.tb00900.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SummaryThe behavioural ecology and breeding biology of the endangered PalilaPsittirostra bailleuiwas studied from 1971 to 1975. The most intensive breeding occurred from June to August, and coincided with peak production of mamaneSophora chrysophyllaseeds, the bir?s major food source. The Palila was able to make adjustments in its breeding to compensate for yearly differentiation in the timing and abundance of this food supply.Sexual chasing and courtship feeding were the most frequently encountered pre‐nesting behaviours. Territory was a mate‐defended area, which later in the nesting sequence was confined to the nest site. A total of 26 nests was found; most were placed on larger branches of mamane trees. Nest construction occurred primarily in the morning hours and lasted up to 20 days. Both sexes took part in nest construction, albeit the male role was minimal. Unless the nest was placed in the terminal fork of a tree, it usually contained a large stick base.The modal clutch size was two; eggs were laid early in the morning and in all cases one per day. Incubation sometimes began with the first egg and lasted 15–16 days. Only the female incubated, and she covered the eggs for about 75% of the daylight hours and throughout the night. Egg hatching was asynchronous, with the first young emerging early in the morning and the second not until later that same day.Only the female brooded, and the rate declined until day15when essentially it stopped. Both parents fed the young by regurgitation, and the number of feedings per hour decreased slightly over the nestling period. It is thought that insects and finely masticated plant material formed the bulk of the nestling diet until about day 5 when mamane seeds became important. Helpers were found at one nest. Young developed slowly and did not leave the nest until 21–27 days old. It is believed that these prolonged nestling periods were able to evolve because of the (former) absence of ground predators. After fledging, young remained with their parents for at least 30 days.Productivity was regulated by small clutch size, low population numbers and by the length of an individual nesting sequence (in that a pair could potentially raise only one brood each year). The primary reason for the endangered status of this bird appears to be the effect of habitat alteration upon a specialist, coupled with the fact that the small effective breeding population and low dis‐persability of the species may have resulted in decreased geneti

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1980.tb00901.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SummaryThe food and feeding ecology of Black‐browed Albatrosses and Grey‐headed Albatrosses was studied from 1975 to 1978 at Bird Island, South Georgia. Two hundred and seventy food samples (averaging 75–85%by weight of the mean chick feed) were collected from adults of each species in February and March. Chicks of both species received meals of the same size, of which half consisted of liquid. The three major components of the solid diet (krill, squid and fish) were similar for both albatrosses. By weight, fish represented about 35%of the diet of both species; squid predominated (50 %) in the diet of Grey‐headed Albatross, and krill (40 %) in the diet of Black‐browed Albatross. Lampreys were confined to the Grey‐headed Albatross and, although squid of similar sizes were taken by both species, Black‐browed Albatrosses took a much greater diversity of squid. Each major prey type was associated with a characteristic amount of liquid in the complete samples and only in the case of krill and lamprey was this lipid‐rich.As these two albatrosses are of similar size, breed over the same period and feed meals of equivalent weight to their chicks at similar intervals, the difference in the composition of the diet is possibly the most significant mechanism of ecological segregation (in the breeding season).Evidence of the effect of krill shortage in drastically reducing Black‐browed Albatross breeding success is presented to support this. The two species have largely non‐overlapping winter oceanic ranges which are probably also correlated with the distributio

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1980.tb00902.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1980.tb00903.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1980.tb00904.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1980.tb00905.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1980.tb00906.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1980.tb00907.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1980.tb00908.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY