摘要:

Barrow's Goldeneye females with broods in the Lake Mývatn district, Iceland, concentrated in a small area in the lake's outlet where the density of blackflySimulium vittatumlarvae, the principal food of the young, was highest. A downstream migration of broods took place as predicted from the growth pattern and emergence of blackflies in the river

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1988.tb00967.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

A total of 126 flightless adult male Teal was caught in 1982 and 1983 in a moulting area in northern Sweden (63° 53′N). The birds were weighed and the stage of development of their primaries and secondaries measured. During the flightless period, the weight of the birds decreased by an average of 10% in 1982 and 19% in 1983. This weight decrease allows the birds to fly before their primaries and secondaries are full‐grown. The weight loss is considered to be an adaptation making it possible, for example, for lighter birds to escape predators sooner after moulting. Birds varied greatly in the dates at which they initiated their flightless period, that is, from the end of June to the end of July. Thus, it is probable that both local birds and birds from distant breeding grounds were present in the moulting

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1988.tb00968.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The breeding of Guillemots was studied in five areas of different breeding density and habitat type on the Isle of May in 1981‐86. Prior to 1981 numbers were increasing at 5 6° per annum but during the study the rate of increase slowed down and from 1983 to 1986 numbers were fairly constant. Adult survival was high, with a mean minimum annual adult survival of 930% (s.e. = 03). Observations in 1986 suggested that the percentage return of colour‐marked immature birds was low, with only l‐6% and 5.5% of second and third year birds being seen. We suggest that poor recruitment was responsible for the levelling off in numbers at the colony.The timing of laying was constant from year to year in 1981‐85 but was later in 1986. It was significantly and inversely related to sea temperature the previous March. There was a consistent ranking in median laying dates amongst the areas, with area 1 (the highest density of birds) always earliest. However, there was no significant difference in synchrony between the areas. Overall breeding success was high (0–71‐0‐82 young fledged per pair). There was no consistent ranking of breeding success with breeding density, habitat type or laying synchrony.The only aspect of Guillemot biology which changed significantly was the daily food intake of a chick which approximately halved during the study period. However, this reduction in food intake had no detectable effect on either the weight of chicks with wing lengths greater than 60 mm or the amount of time off‐duty breeders spent at the site. Both of these parameters were still consistent with conditions being fa

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1988.tb00969.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The diet of King PenguinsAptenodytes patagonicusat Macquarie Island was studied between November 1984 and November 1985 based on stomach flushed samples (obtaining 93% of the total stomach content) from ten birds each month. The mean stomach content mass of the 118 samples was 923 0 g. Percentage by number, percentage by weight and dietary coefficient analysis all showed the main prey of the penguins to be myctophid lantern fish of the speciesElectrona carlsbergiandKrefftichthys anderssoni.Juvenile fish of both species were eaten from December to July, and adults in August and September. Cephalopods were relatively unimportant in contrast to previous indications. The amount of food brought ashore and the composition of the diet varied over the year, withK. anderssonithe dominant food in all but the winter months whenE. carlsbergireplaced it as the principal food item.

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1988.tb00970.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Observations at the North Shields Kittiwake colony between 1982 and 1984 showed over 100 potential recruits (birds of breeding age) associated with the colony, only about 40% of which were actually recruited. In addition, there were younger birds which visited the colony. The origins, age structure and intercolony movements of members of the pool of prospectors have been examined. Porter&Coulson (1987) demonstrated that recruits are heavier than prospectors, implying that they are in better body condition. Three further prerequisites for breeding in Kittiwakes are recognized: the age of recruits is at least three years; all birds which recruit are present at the colony at least one year prior to breeding; and recruits show a high degree of attachment to colony as illustrated by their colony and nest site tenacity, attendance and early arrival. The results suggest that there is considerable selection of individuals at the time of recruitment; the mechanism for this has yet to be examined.

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1988.tb00971.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

It appears that chicks are selected to run away and seek adoption in a foster‐family when the level of investment they receive falls below a certain threshold. Predictions based on this hypothesis are in agreement with the available evidence in the literatur

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1988.tb00972.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Samples of Purple Sandpipers were captured around the coasts of Britain. Analysis of their bill‐length distributions enabled the sex ratios and percentages of ‘long‐billed’ and ‘short‐billed’ birds at each locality to be estimated. The sex ratio for the ‘long‐billed’ population was estimated to be one female to 2–11 males, and one female to 1 ‐34 males for the ‘short‐billed’ population. During winter, proportionately more ‘long‐billed’ birds occurred in northern and western Scotland, Wales and southern England, whilst ‘short‐billed’ birds predominated from Kincardine to Yorkshire. The total sizes of the ‘long‐’ and ‘short‐billed7’ populations werec.15 000 and 4000, respectively. ‘Short‐billed’ birds started arriving from Norway in early July. ‘Long‐billed’ birds did not arrive until late October. Their origins are as yet unknow

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1988.tb00973.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The outer Bay of Fundy, eastern Canada, is an important feeding area for migrant Grey and Red‐necked PhalaropesPhalaropus fulicariusandP. lobatusin late summer. The birds feed on copepod‐sized zooplankton, brought to the surface by the passage of strong tidal streams over shallow, rocky ‘ledges’, and concentrated there in upwelling and convergence ‘streaks’. Feeding phalaropes are significantly more abundant in the ‘streaks‘ than in adjacent ‘contro’ areas. Red‐necked Phalaropes are the more common species; they prefer the New Brunswick shore, where copepod biomass is high and the species‐community is dominated by large, Stage VI‐VCalanus finmarchicus. Grey Phalaropes occur mainly on the Nova Scotian side of Fundy, where the copepod biomass, and the dominant species, are smaller. The feeding habits of both species, and their non‐breeding distributions, are reviewed. It is concluded that upwellings, convergences, and other oceanographic phenomena that concentrate zooplankton at the surface are the principal factors influencing the pe

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1988.tb00974.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Environmental characteristics associated with siting of the incubation mounds of the megapode, the Australian Brush‐turkeyAlectura lathamiwere investigated in three rainforest locations in southeast Queensland. Seventeen environmental variables were measured for 52 mounds and 137 non‐mound sites. Most mounds were constructed on top of old mounds which had not been used during the previous year. A Discriminant Function Analysis obtained a clear separation between mound and non‐mound sites, based primarily on three variables: (1) the number of saplings growing within the mound or centre of the site: this was considered to be a result of the germination of seeds raked in earlier years; (2) the proportion ofLantana camarathicket occupying the site. Approximately half of the mounds constructed during a season were abandoned by their constructor due to expulsion by a neighbouring male. Brush‐turkeys could more easily establish mounds next to thickets since the efficiency of defence by other males was reduced in these areas; and (3) the openness of the canopy. Areas with greater canopy cover provided two important mound resources: a good supply of leaf litter, and protection of the mound from dess

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1988.tb00975.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Growth patterns of nestling Collared DovesStreptopetia decaocto, WoodpigeonsColumba palumbus, Feral PigeonsC. liviaand Stock DovesC. oenas, in Britain were compared. Open‐nesting Collared Doves and Woodpigeons left the nest at about 60% of adult weight, hole‐nesting Stock Doves at adult weight, and partial hole‐nesting Feral Pigeons at an intermediate stage. Other species of pigeons and doves studied to date also fit this pattern. Stock Dove nestlings reared in nest‐boxes reached heavier weights and left the nest later than those in more exposed sites. These results were correlated with differential predation pressure on open‐ versus hole‐ne

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1988.tb00976.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY