摘要:

SummaryNestling survival and nestling weights in P.domesticusandP. montanuswere studied in 1961 and 1963–64 at Oxford. This paper concludes a study of factors influencing the reproductive rate.Taking all losses into account,P. domesticusreared an average of 1.6 nestlings per brood (45%) andP. montanus2.7 nestlings per brood (59%). About a third of all broods of both species failed completely to survive the nestling period. InP. domesticusthese failures were most numerous in the middle part of the breeding season and are attributed to nutritional deficiencies derived from unsuitable food provided as a consequence of a seasonal food shortage, but inP. montanuscomplete brood failures occurred mostly in the second half of the nestling period and are attributed to predation.43 broods ofP. domesticusand one brood ofP. montanuswere weighed daily. Those of P.domesticuswere classified as (1) successful broods—in these some nestlings died in the larger brood‐sizes, apparently through starvation; (2) long‐lived unsuccessful broods—in these the nestlings died at intervals and failure was attributed to nutritional deficiencies; and (3) short‐lived unsuccessful broods. A slight decrease in the weights of nestlings in successful broods at the end of the nestling period is attributed to the utilization of insulating fat facilitated by the completion of the feather covering. Nestlings of both species left the nest at 88–89% of the adult weight.Taking all “successful” broods together, the percentage survival rates on nestling day 131/2(day of hatching = day1/2) inP. domesticuswere 81–82% in b/2–3, 70% in b/4 and 56% in b/5 (a situation paralleled in this respect by P.hispaniolensis), but in P.montanusthey werec. 82% in all brood‐sizes. Hence, in P.domesticusb/4 probably gave rise to the largest number of nestlings reared per brood, while inP. montanusmost nestlings were produced by the largest brood‐size. Weighings of many broods on day 131/2showed two trends in the weight of the nestlings: (1) in both species the weight of the nestling decreased as the number of survivors from each initial brood‐size decreased; (2) between successive initial brood‐sizes the weight of the nestling of P.domesticusdecreased with increasing brood‐size but in P.montanusthere was no change.The losses in the larger broods of P.domesticusoccurred mostly in the first half of the nestling period—apparently in association with the asynchronous hatching of the eggs and as a consequence of the limitation on the feeding frequency of the adults. Nestling survival was lowest in the larger broods in the middle of the breeding season and contrasted with the mid‐season increase in mean clutch‐size. It is suggested that in the study area there was a (possibly unnatural) shortage of food suitable for nestlings in the middle of the season.It is suggested that inP. domesticusthe unexpectedly low feeding frequencies of the adults with large broods, apparently causing their low survival rates, may be an adaptation evolved to obtain the maximum amount of food in the presence of other adults which would be attracted to a food source by higher rates of activity.The breeding success calculated from data derived from the whole of this study was 35% for P.domesticusand 49% for P.montanus(2.9 and 3.9 nestlings per breeding pair per year respectively).It is suggested that the population of P.domesticuswas much closer to a critical limiting factor, e.g. food supply, than that of P.montanus. This may account for the striking differences between the two species in their nestling survival rates and their nestling weights in relation to brood‐size; in particular, the success of the larger broods of P.monta

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1970.tb00071.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SummaryIn the windswept and treeless Falkland Islands, the natural vegetation has been seriously depleted by two centuries of extractive farming. One habitat—mature Tussock‐grass—is of vital importance to the resident birds, and those Tussock‐covered islands that remain in a nearly natural state can support a far greater density and variety of bird species than any areas on the mainland.Kidney Island maintains a diverse avian fauna because it offers abundant cover, nest‐sites, nest materials and food. In and around the dense mature Tussock‐grass which covers about 90% of the surface, 28 bird species nest on the island; 18 of them occupy one or other of the six minor habitats which can be distinguished in the Tussock‐grass. The nest‐sites and interrelationships of these breeding specie

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1970.tb00072.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SummaryIn compiling this new list, which is based on Howard Irby's ‘Ornithology of the Straits of Gibraltar’ (1895) but is confined to the area of Gibraltar itself and its surrounding waters, the results of three years' observations from 1965 to 1968 together with other recent records and literature have been used. Of the 198 species listed 118 are passage migrants and a further 36 winter visitors. The introductory sections of the paper contain a short description of the climate and topography of Gibraltar showing why the Rock can support only a small number of breeding species and why so few water birds find a place in the list. A few general observations and tentative conclusions on the migration of soaring birds and passerines in relation to weather conditions, particularly wind direction, are included as a background for the large number of passage migrants which figure in the l

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1970.tb00073.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SummaryThe pelagic distribution of the FulmarFulmarus glacialisoff eastern Canada has been used to test Fisher's (1952, 1966) hypothesis that Fulmar numbers are controlled by the availability of offal from the fishing industry. Fulmars are abundant on the fishing Banks off Newfoundland but not on those off Nova Scotia; by contrast, they are fairly common in the unfished waters south of Greenland. The Newfoundland and Greenland waters are colder than those off Nova Scotia, and it seems likely that temperature and other oceanographic factors, not fish offal, control Fulmar distribution in the western Atlantic. Since the ringing returns show that many of these Canadian birds are from British colonies, it is possible that fish offal may not be the key factor in the eastern Atlantic either.Since there are no reliable quantitative data on the Fulmar's diet, it is difficult to suggest a specific alternative. However, the Fulmar is, over much of its range, a cold‐water species; it may eventually be possible to interpret Fulmar distribution in oceanographic terms, the key factor being its macroplanktonic food. However, the Fulmar population in the warmer waters of the eastern Atlantic remains an anomaly; it is not yet possible to explain the differences in ecology between the eastern and western Atlantic birds, either in oceanographic terms, or by the availability of fish offa

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1970.tb00074.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SummaryField and museum measurements confirm the existence of a morphologically distinct southern subspecies of Gentoo PenguinPygoscelis papua ellsworthi, breeding on the Antarctic Peninsula and the South Orkney and South Shetland Islands. Morphological and zonal differences between other island stocks are noted, but present evidence does not support further definition of subspecies.

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1970.tb00075.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SummaryA visit was made to Malamfatori, on the western shore of Lake Chad, Nigeria, from 22 March to 13 April 1967, with the principal aim of studying Palaearctic migrants in relation to the environment. About 2,400 Palaearctic migrants of 29 species were mist‐netted in beds of bulrushTypha australisand thickets of saltbushSalvadora persica. Some 300 of these were collected for fat analysis; the remainder were released after measurement and ringing, and provided 275 retraps during the course of the study. Data were supplemented by further netting by A. J. Hopson in late April and May.Yellow WagtailsMotacilla flava, Sedge WarblersAcrocephalus schoenobaenusand WhitethroatsSylvia communiswere abundant and were studied in greater detail than other species. Yellow Wagtails fed almost exclusively on midges, particularly the abundantTanytarsus spadiceonotatus. Sedge Warblers fed on small insects and spiders, and Whitethroats onSalvadorafruits. Sedge Warblers and some other chiefly insectivorous species turned to a diet including berries shortly before emigrating.Changes in weight during the course of the day were difficult to investigate, but were probably bimodal. Good correlations of weights with wing‐lengths were obtained for species for which many data were available. Pre‐migratory fattening did not occur synchronously in all populations of a species, but once it started in an individual it proceeded at a constant rate of 0.2 g/day in Sedge Warblers and 0.6 g/day in Whitethroats. Predation pressure probably ensured that individuals emigrated immediately they attained their maximum pre‐migratory weight, although some Sedge Warblers and Whitethroats left the area before attaining maximum weight.Differences between the mean weight curves of first‐caught and retrapped birds are discussed, and it is concluded that in some species there were both through‐migrant and temporarily‐resident populations at Malamfatori.The mean weights per day of Whitethroats, Sedge Warblers and also Reed WarblersA. scirpaceuswere falling in late March, and slight changes in the weather, particularly temperature, may have been responsible. In mid‐April there was a “rush” of lean Whitethroats, which are thought to have originated to the SW in Nigeria.Yellow Wagtails, Sedge Warblers and Whitethroats deposited up to 40% fat/live weight; Sand MartinsRiparia ripariahad up to 28%, and a small sample of RuffsPhilomachus pugnaxup to 17%. In the case of Sedge Warblers, fat reserves were sufficient for crossing the Sahara both to the north and to the northeast.Contrary to the findings in some previous lipid studies, the fat‐free dry weight and water content increased during fattening. The fat‐free dry weight increase was about 34% in Yellow Wagtails, 18% in Sedge Warblers, and 35% in Whitethroats. The tissues involved in this increase were not investigated, but a study of Yellow Wagtails at Malamfatori in 1968 (in prep.) suggests that the pectoral muscles hypertrophy during fat deposition sufficiently to account for nearly all of the increase in fat‐free dry

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1970.tb00076.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SummaryThe moult of primaries, secondaries, and rectrices in two closely‐related gulls, the Great Black‐backed GullLarus mavinusand the Glaucous GullL. hyperboreus, was studied in Iceland. Both gulls moult their primaries in an extremely regular sequence, starting with the 1st (innermost) and ending with the 10th (oiltermost) feather. Usually two, less often one or three, primaries are growing per wing during the primary moult, which lasts for about six or seven months. Growlng primaries were estimated to lengthen on the average by 8.7 mm per day inmarinusand 7.8 mm per day inhyperboreus.The secondaries, usually 24 in number, are shed in two moult waves, one starting with the innermost feather soon after the start of the primary moult and then progressing slowly outwards, the other beginning with the outermost secondary after the primary moult is about half completed and then progressing rapidly inwards. The moult is completed just before the end of the primary moult as the two moult waves meet at about the 16th secondary. There are no marked differences between the two gulls in the moult of secondaries.The moult of rectrices shows large variations in both species, some feathers being much more irregular than others in their time of shedding. In both species, indications of an obscured centrifugal pattern of replacement are seen, although the 5th (next to the outermost) rectrix is usually the last one to be shed. Significant differences were observed between the two species in the degree of regularity of shedding of some feathers and in the average position in the moulting sequence of others. The moult of rectrices starts soon after the moult of primaries is half completed. The feathers are then shed in rapid succession, and the moult is completed some time before the end of the primary moult.The need for good powers of flight at all times is undoubtedly the reason for the protracted primary moult. This in turn causes the moult to start early, in adults sotnetimes before the eggs are laid; immatures moult even earlier than this. The rectrix moult and the main part of the secondary moult do not begin in adults until the young have fledged, but then progress very rapidly. Presumably, the loss of some of these feathers would impair the flying ability to an extent sufficient to make it difficult for the gulls to care for their young, while the rapid moult is necessary in order for the replacement of these feathers to be completed by the time the primary moult is o

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1970.tb00077.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SummaryThe paper is concerned with the relative importance of environmental changes and social stimulation in bringing about synchronized social breeding inPloceus cucullatusandMelanopteryx (Ploceus) nigerrimus. Field work was carried out in central Uganda.Observations on a single colony of each species extending over a complete breeding period showed that breeding started abruptly with the arrival of a large number of males and the construction of new nests. The majority of females arrived later within a relatively short space of time. Subsequently the number of birds and the amount of activity declined gradually. Nests were repeatedly destroyed and reconstructed in the same positions. InP. cucullatusan entrance funnel was generally added only after occupation of the nest by a female.Studies extending over a large number of colonies showed that main breeding seasons correspond approximately with the two rainy seasons each year. Isolated colonies may be active between seasons, however.Nest‐building and breeding are highly synchronized within colonies. Uniform responses to rain may partly account for this synchrony, but fluctuations of activity in neighbouring colonies are relatively unsynchronized, suggesting that social stimulation is also an important factor. This is supported by direct observations of social interactions and by the fact that small colonies are relatively less successful than larger ones, apparently because the pair‐formation process may fail in the absence of sufficient social stimulat

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1970.tb00078.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1970.tb00079.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1970.tb00080.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY