摘要:

SummaryA study of the breeding biology, feeding ecology, and behaviour of the Little Auk was carried out on Horse Head Island (73° 38′ N, 57° 08′ W) in west Greenland between July and August 1974. Distinct subcolony groups were recognized within the colony. During incubation, attendance at the colony increased to a peak between 2100 and 2400 h, with large rafts building up on the sea before engaging in aerial flights and then settling on land. During the nestling period, this pattern changed with further peaks at 0600 and 1800 h, and a decline during the afternoon, particularly during the late nestling period.Little Auks fed exclusively on copepods and amphipods (94%Calanus finmarchicus) usually captured within 2.5 km of the colony. Feeding rhythms fitted closely the known diurnal vertical migrations ofCalanuswith peaks between 2200 and 0800 h. Some individuals within subcolony groups showed synchrony of feeds, mainly between 1800 and 2400 h. The mean number of feeds to a chick in 24 h was 5.25. Growth rates of young were comparable between all four experimental groups and controls, although the latter attained higher weights. Mean daily weight increases were constant until 18 days of age when they declined sharply. This was not reflected in a change in mean daily weight increases with date and so suggests that food availability had not declined. Instead there was a reduced feeding rate to chicks from age 21 days to fledging.Breeding success was 50 %, mainly the result of egg desertion and predation by Arctic Foxes, and this may have been reduced by our own activities. Behaviour postures and the responses they elicited are described together with the diurnal patterns of different activities. Aerial flights are also described and their possible function discussed.It is concluded that the shortness of the time when abundant food is available has encouraged close breeding synchrony and this is achieved by mass flights and rafting on the sea beside the colony, and subdivision of the colony into groups with communal behaviour close to the

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1981.tb00168.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

SummaryThe foods of Great and Sooty ShearwatersPuffinus gravisandP. griseusare described from birds collected off eastern Canada. There was a broad overlap in diet, but Great Shearwaters tended to take more squid and tough‐bodied fish such as mackerelScomber scombruswhile Sooties took more euphausiidsMeganyctiphanes norvegicaand soft‐bodied fish such as HerringClupea harengus. These differences are apparently related to differences in bill structure and in the degree of adaptation to underwater swimming.The birds appeared to feed opportunistically on whatever prey was locally available in the size‐range between euphausiids and small fish and squid:Meganyctiphanesoff southwest Nova Scotia, spawning and post‐spawning capelinMallotus villosusoff eastern Newfoundland, and migrating squidIllex illecebrosuson the Grand Bank. Possible factors influencing prey selection are discussed. It is suggested that the timing and routes of the birds' migrations in the North Atlantic are related to the exploitation of such local concentrations.Despite the overlap in diets, differences in the distributions of the two species rule out the possibility of significant competition for common food re

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1981.tb00169.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

SummaryThis paper reports on part of a three‐year study into the biological significance of variation in body size of individuals from a single population of Great Tits in Wytham Woods near Oxford, from 1973 to 1976. It is a reasonable hypothesis that the body size of an individual is controlled partly by heredity and partly by environmental factors. Genetical factors by themselves are shown to account for nearly three‐quarters of the total observed phenotypic variance of body size. Of the likely environmental factors considered, only the date of hatching (in 1973) and an annual difference in body size are shown to have significant effects.Previous workers have shown that heavier fledglings have a better chance of surviving the immediate post‐fledging period than lighter fledglings (e.g., Perrins 1965). It had been postulated that this differential survival rate might be due to variations in the fat reserves of fledglings. However, the data presented here suggest that this hypothesis is unlikely, and that the body size of fledglings has a more significant influence. The aggressive behaviour of fledgling Great Tits towards one another may be the mechanism responsible for this since it is shown that larger fledglings tend to dominate smaller fledg

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1981.tb00170.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

SummaryEvidence for reduction of clutch size in insular passerines is presented. Average clutch sizes for the Catbird, Cardinal and White‐eyed Vireo were reduced 14.0, 18.2 and 30.7%, respectively as compared with coastal North American populations from similar latitudes. Differences are highly significant. Clutch size in the Eastern Bluebird was not reduced. Trends in latitudinal and longitudinal variations of clutch size in North America are examined. With the exception of a slight latitudinal gradient in coastal populations, no consistent trends existed. There is no evidence for reduced variability in clutch size or increased egg size in the Bermudan populations, but both these parameters may show some response to combined effects of latitude and longitude in continental populations.Reduction of clutch size in insular nidicolous birds is consistent with both the Lack‐Ashmole resource limitation hypothesis and Cody's energy allocation hypothesis. In the absence of experimental evidence for life history optimization in response to K‐selection, the modified Lack hypothesis seems suffi

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1981.tb00171.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

SummaryAdditional information on 15 species of New Guinea kingfishers is presented:Alcedo atthis(range, habitat),A. azureaandA. pusilla(ecological separation),Ceyx lepidus(foraging, habitat),Melidora macrorhina(affinities, nocturnal habit),Clytoceyx rex(foraging),Dacelo leachii superflua(treehole nesting),D. tyro(reactions withD. leachii), D. gaudichaud(social organization, antiphonal calling, territory size, habitat),Halcyon torotoro(feeding, defence display),H. nigrocyanea(habitat),H. macleayiiandH. sancta(habitat, wintering territory),Tanysiptera dana(habitat),T. Sylvia(distribution of resident and migratory subspecies). Possible ecological separating mechanisms are suggested for the kingfisher community of rainforests. Abundance at one lowland site is discussed.

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1981.tb00172.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

SummaryAn analysis is made of over a thousand precise bird breeding records for a forest area in West Cameroon. In the lowland forest there is no universal breeding season although most families have a preferred nesting season. On the other hand. in the montane forest breeding is seasonal and takes place in the drier months. These conclusions are supported by field observations and by the examination of over 5000 birds for gonad state, plumage wear and moult.The remarkable difference in seasonality between the lowland and montane avifaunas is discussed with reference to climate, particularly to the mist which envelops the montane forest in the rainy season.

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1981.tb00173.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

SummaryObservations were carried out on a colour‐ringed population of Dunnocks. During the winter, regular feeding groups formed at feeding sites, stable in composition, space and time. Dominance hierarchies formed and were weight related. Males were significantly heavier than females. The mean size of winter home‐ranges was not significantly different from the mean size of breeding territories.Three categories of breeding territory were established: solitary males, male‐female pairs and pairs plus a male helper. There was one case of a bigamous male plus a helper. Pairs plus a helper had significantly larger territories than pairs alone; however, pairs raised significantly more fledglings. Five pairs produced a total of 23 fledglings, whereas four groups (pairs plus a helper) only produced seven fledg

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1981.tb00174.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1981.tb00175.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1981.tb00176.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1981.tb00177.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY