摘要:

SummaryThe Bearded BellbirdProcnias averano, a medium‐sized sexually dimorphic cotingid, was studied for three years in the Northern Range of Trinidad.Its preferred habitat is primary forest at altitudes of 500–1,000 feet and with a rainfall near 100 inches. It is entirely frugivorous, taking mostly drupes. The seeds of the fruits eaten are regurgitated and nearly 2,000 were collected from below the male's calling perch and below nests. Most were from the families Lauraceae and Burseraceae, whose fruits have particularly nutritious pericarps.Adult males own a calling territory from which they call throughout most of the day, and throughout the year except for the period of moult. In each territory there are special saplings where display and mating take place.Only males call; the females are voiceless. The call is loud and far‐reaching. In TrinidadP. averanohas only two calls, the Venezuelan birds have a third more musical call which appears to have been lost by the Trinidad bellbird during the past 60 years.Both males and females visit the adult male in his calling territory. Here he performs a ritualized display to the visitor, which shows off his black and white plumage, the beard of wattles, and also a bare patch on the thigh. The visit of the female may culminate in mating. All aggressive behaviour observed was between males disputing over calling territories.The female builds the nest, incubates, and rears the chick on her own. The very inconspicious nest is built of twigs that readily interlock. Nearly all the twigs are from two species of tree, and it is suggested that the specialized nest‐material may be essential, as the female bellbird builds only with the breast and feet. The clutch consists of a single egg. The incubation and fledging periods are both long, 23 and 33 days respectively. The female's visits to the chick are infrequent, brief, silent and inconspicuous. Many details of breeding behaviour indicate that the inconspicuousness of the nest is of paramount importance.The nestling is fed on fruit which the female regurgitates. The main breeding season is from April to July with a minor one in October and November. It takes two and a half years for the male to attain fully adult plumage, and at least two years to achieve a completely adult call.The relationship between type of nest, clutch‐size, feeding habits and sexual bonds in tropical forest birds is discussed. The bellbird is an extreme example of a species in which the need for a very inconspicuous nest and a diet of fruit have combined to promote polygamy, with the emancipation of the male from the nest, and to reduce clutch‐size to a minimum.The bellbird's structural adaptations to its method of feeding in flight are discussed and a comparison is made with the birds of paradise. The male's adaptations for its primary function of self‐advertising are compared with the parallel adaptations evolved in the rel

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1970.tb00109.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SummaryA population of Common Shelducks on the Ythan Estuary was studied intensively from December 1961 to August 1964, with special attention to territoriality and population regulation.Many of the shelducks in this population establish mutually exclusive territories; the others (usually about one third of the population) remain together in a communal flock. Both members of territorial pairs take part in territorial defence.Territory size is determined by the immediate topography of the area and by the limits of tolerance of the owner. The distribution of territories was found to be related to the distribution ofHydrobia ulvae, which is the staple item in the shelducks' diet.Territories were usually occupied by the same birds year after year. The number of territories remained constant at 71 ± 1 throughout the three years of the study.The first birds to return in the spring were not necessarily the first to take up their territories. Some territories were left unclaimed (at least for the greater part of the day) until the end of April. At no time were interlopers or neighbours ever seen trying to establish themselves in these unoccupied territories.Territories from which both birds were experimentally removed were reoccupied by birds from the surplus flock, usually within a matter of days. When females of territorial pairs were removed, the surviving males invariably deserted their territories, but when the males were removed, the females remained on their territories and eventually acquired new mates

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1970.tb00110.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SummaryThe yellow or orange‐brown colour on the breast feathers and to a lesser extent on other feathers of the Great White Pelican in a breeding colony on an island in Lake Shala, Ethiopia, is due to the presence of ferric oxide.The feathers most probably become stained when the birds are in the water, and the source of the ferric oxide may be iron–rich silt carried into the lake by the Gidu Ri

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1970.tb00111.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SummaryUntil recently, the Herring GullLarus argentatusand the Glaucous GullL. hyperboreuswere completely allopatric in western Europe, although having overlapping distributions in Canada and the Soviet Union. But beginning about 1925–1930 a large‐scale invasion ofargentatusfrom the Faroe Islands and/or Britain into Iceland occurred, resulting in extensive hybridization withhyperboreus, already present there. The hybrids are viable and apparently fully fertile.In the summers of 1964–1966 371 gulls were collected from breeding colonies in various parts of Iceland and the samples analysed by the use of hybrid indices based on the colour of the five outermost primaries. The populations of northwestern Iceland, where the greatest concentration ofhyperboreuswas found at the time of theargentatusinvasion, were found still to consist largely of purehyperboreus, with 18–23% of the birds showing signs ofargentatusadmixture. In eastern Iceland, whereargentatusfirst appeared in numbers, and along the south coast, birds of hybrid origin predominate, 3–43% of the birds being pureargentatuswhile purehyperboreusare absent except for one colony in southeastern Iceland where they made up 23% of the birds. Significant differences in composition are found among several of the colonies of eastern and southern Iceland, and possible reasons for this are discussed.Among 53 mated pairs no deviation from random matings with respect to hybrid indices was indicated. The high proportion of pureargentatusfound in some colonies in spite of this indicates that pureargentatusare still immigrating from abroad. Two colonies in eastern Iceland sampled both in 1965 and 1966 showed a significant change in composition towardsargentatus, further evidence for continued immigration ofargentatus. A few other colonies have changed in the same direction over longer periods.Although there must be some differences between the two forms in ecological requirements as shown by their distributions, their ecologies appear similar in Iceland. Both forms take a large portion of their food from the intertidal zone of the sea‐shore, and although a slight difference in the selection of foods from the shore was seen in winter in one locality, this probably did not have a genetic basis. However,argentatusmay feed to a larger extent on refuse thanhyperboreus. This may enableargentatus‐like birds to occupy the relatively barren (with respect to intertidal foods) east coast of Iceland in numbers.An examination of several hundred museum skins ofargentatusandhyperboreusfrom other areas shows that occasional hybridization occurred in western Europe long before the extensive contact was established in Iceland, but gene flow between the two was always limited as their ranges were widely separated. The two gulls are effectively reproductively isolated from each other where synipatric in Canada, while the situations in Alaska and in parts of the Soviet Union are unclear.Since the area of overlap without hybridization is much larger than the area of hybridization, the two forms are best regarded as separate species. Future studies may show in which direction the hybrid situation in Iceland will develop, but meanwhile it is suggested that the hybrid populations in which birds of hybrid origin amount to 50% or more be referred to asLarus argentatu

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1970.tb00112.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SummaryChristmas Island, at 2° N, 157° W in the Central Pacific Ocean, supports 18 breeding species of sea‐birds. Data on the breeding seasons collected by the authors and other visitors to the island are analyzed in individual species accounts. Population estimates are given, the distribution of each species on the island is outlined, and for some species information on the sexual and moult cycles of marked individuals is presented. The Discussion concerns the ultimate and proximate factors controlling breeding seasons and the role of social factors in maintaining breeding synchrony in sea‐birds, the diversity of the breeding regimes exhibited on Christmas Island (summary and analysis in Fig. 2 and Table 5), and comparison of these regimes with those found in the birds of Ascension Island and the Galapagos Archip

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1970.tb00113.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.tb00114.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.tb00115.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.tb00116.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.tb00117.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.tb00118.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY