摘要:

SUMMARYWideawakesSterna fuscatawere studied on Ascension between October 1957 and April 1959. As shown by Chapin, breeding in this species occurs every nine and a half months on Ascension, and two complete breeding periods were observed. Some of the birds are close to the island even in the non‐breeding period, and many settle on the breeding ground at night during the two months before breeding begins, although they suffer serious predation from cats at this time.The Wideawakes breed in dense colonies, usually on rocky ground. The single egg is incubated by the parents alternately, in shifts which on Ascension last up to six days, probably indicating that food cannot be found quickly, close to the island. The fledging period is long, but the rate of development flexible: the young can survive long periods on very little food, but grow relatively fast when given more food. In spite of this adaptation many young died of starvation in the second breeding period observed, while those which survived took longer to fledge than the chicks raised in the previous breeding period. The chicks also suffered severe predation, from frigate birds when very young and from cats when older. Together, these factors resulted in strikingly low breeding success.Individual Wideawakes on Ascension breed at intervals of 41–51 weeks, and between successive breeding periods undergo a complete moult: they finish one moult before returning to breed, but may start the next moult before their chicks are full‐grown. The length of the interval (9 months) between the start of laying in successive breeding periods appears to be determined by the time required for breeding activities, a complete moult, and an assembly and courtship period during which social stimulation is probably important.In an appendix are listed the recorded times of breeding of Wideawakes in all parts of their range: previously undiscerned six‐monthly or non‐seasonal breeding is documented for several l

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1963.tb06757.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1963.tb06758.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

SUMMARYThe Fairy Tern was found to have an annual breeding season at Ascension, laying about January. Individual pairs laid on the same ledge in successive seasons with an interval of close to a year. The growth of the chick was variable and slow, a characteristic shared by other Ascension species. The breeding success was higher than in other species of the area, being about 30% in two seasons. The moult was found to be somewhat irregular and, on the available data, puzzling, an unusual feature by comparison with the other local terns. Food and feeding methods are described; pelagic fish of many species were taken. Some observations on behaviour, and some adaptations to cliff‐nesting (particularly anti‐predator responses, in spite of an absence of predators at Ascension), are discus

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1963.tb06759.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1963.tb06760.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

SUMMARYBird bones and feathers found in phosphate deposits and fumaroles on Ascension during the B.O.U. Centenary Expedition were used to supplement the historical records in building up a picture of the original avifauna of the island. The remains which can be definitely identified provide strong circumstantial evidence that the sea‐bird colonies on the main island included at least the following species:Oceanodroma castro, Phaethon aethereus, Sula sula, S. dactylatra, Fregata aquilaandSterna fuscata:a skull apparently ofGygis albawas also obtained. No remains definitely referable toPhaethon lepturus, Sula leucogasterorAnous stolidushave yet been found, but it seems very likely that these species also nested in numbers on the main island of Ascension, whileAnous tenuirostris, which still nests on the cliffs of the main island, doubtless also did so in the past.In addition to sea‐birds, a skull and a tarso‐metatarsus of a small rail, found in separate localities, probably represent the extinct flightless species described by Peter Mundy. The rail whose bones were obtained is provisionally considered as a new member of the genusRallus.The only surviving species that is endangered locally is the Red‐footed BoobySula sula: the history of this species on Ascension is di

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1963.tb06761.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

SUMMARYIn this paper the bird bones collected in three separate localities on St. Helena during the British Ornithologists' Union Centenary Expedition to Ascension Island are catalogued and described. At Prosperous Bay there are deposits which appear to be only a few hundred years old, containing many intact bird bones, referable toPuffinus assimilis/lherminieri, Pelagodroma marina, Sula sula, Fregata ariel, and a new railAphanocrex podarces.In Dry Gut, north of Bencoolen, are apparently older deposits with bones of a medium‐sizedPterodromasp. and a humerus ofUpupa epops.On Sugar Loaf Hill are extensive deposits which may be very old, containing fragmentary bones of a largePuffinussp., ofPuffinus assimilis/lherminieri, Pelagodroma marina, and at least one species of columbid.There is now evidence that thirteen species of oceanic birds have bred on St. Helena at some time (plus one—Sula leucogaster—whose status is still uncertain). Of these, only six species are now known to breed on the island, though two more may do so.The only surviving native land‐bird isCharadrius sanctae‐helenae, but at least three additional species were present in

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1963.tb06762.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

SUMMARYAscension Island Frigate Birds (present population 8,000–10,000 breeding adults) were studied on Boatswain Bird Island between November 1957 and April 1959. Eggs were laid throughout the year, but a breeding season of eight to nine months (April to November or December) was apparent in 1958 and there was evidence of a similar season in the previous year. The birds tended to nest in groups, at densities varying from one or two to over 60 per area of 50 square metres; some nested at densities of two or three per square metre. Nesting success was highest among early breeders, out‐of‐season breeders and those breeding in low‐density groups, and was very much lower in the areas of dense nesting; greatest losses were among eggs and young chicks, and a nesting success of 15°‐20° is indicated for the population as a whole. Courtship, nesting and growth of the chicks ar

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1963.tb06763.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

SUMMARYAt a breeding colony on Ascension, many Black Noddies remained throughout the year. The main part of the paper describes their behaviour, with special reference to daily rhythm, sunning, absence of “panics”, nesting (with possible value of the birds' own guano for cement), fighting, and courtship (with details of ground and aerial displays), copulation (apparently rare) and the behaviour of parents and young.On Ascension the birds nest on small cliff‐ledges, elsewhere they also use trees, both kinds of sites being relatively inaccessible to ground predators, unlike the majority of terns, which nest on the ground. As with the Kittiwake, another cliff‐nesting species which has diverged from ground‐nesting stock, a number of the Black Noddy's peculiarities can be related directly or indirectly to its nesting site. Indeed the occurrence in just these two species of two features absent in their ground‐nesting relatives indicates that there are some cliff‐nesting adaptations which had previously been overlooked. The Black Noddy's adaptation in this respect can be summarised as follows:Cryptic adaptations lost.Cryptic plumage of nestling and juvenile. Dispersal of egg‐shells and droppings.Adaptations acquired, and their consequences.Shortage of nest‐sites, focussing territory on nest, with consequent increasing, though not exclusive, importance of Bridling as “song”. Allopreening between mates. More elaborate nest‐building, with gathering of material (if available), which is cemented together with guano; side‐stepping and depressing tail when shaping nest. Young intolerant of others; crouch if threatened instead of running; peck at feet of intruders, or beak‐hide to appease attacks, precocious development of adult (threat?) plumage.The Brown Noddy is the closest relative of the Black, and what little is known of its breeding biology suggests it is less specialised for nesting above the ground, and that its ability to nest on the ground as well as in bushes and trees allows it to breed in localities wher

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1963.tb06764.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

SUMMARYThree colonies of Brown Noddies on stacks north of Georgetown, Ascension Island, were visited 24 times between November 1957 and April 1959. During this period there were two main breeding seasons, about a year apart, but in each season there was both an early and a late peak of laying: rollers washing over the stacks may have been partly responsible for this. The moult cycle of the Brown Noddies was probably an annual one, but on Ascension there appeared to be no tendency for moult to stop during breeding: this situation contrasts with that found in other populations of the species. A small number of food samples were obtained, which showed that the diet of the noddies included a variety of fish and some squid. Young Brown Noddies in many parts of the world show a polymorphism in down colour which is still very poorly known; on Ascension most chicks are almost white, about a sixth more or less dark. Diagrams showing the growth of young noddies are given. The age and state of development at which young Brown and Black Noddies and Fairy Terns first fly are considered, and the reasons for the differences between different species and populations are briefly discussed.

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1963.tb06765.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

SUMMARYThe ways in which the numbers of tropical sea‐birds might be limited are considered; it is argued that food is the only factor likely to be generally effective in limiting numbers, but it seems improbable that food shortage could exert a density‐dependent control of the mortality of the birds outside the breeding season.Wynne‐Edwards' hypothesis that colonies of sea‐birds are able to keep their own numbers below the level at which food shortage would become acute, primarily by exerting control on the output of young, is rejected as unproven and improbable.It is suggested that colonies of tropical oceanic birds deplete the food in the waters round them, and that as the populations increase competition for food becomes more intense, and relatively fewer adults succeed in raising chicks. This would provide a density‐dependent control of the output of young and could regulate the numbers of the birds.The peculiarities of long‐lived sea‐birds (e.g. clutches of one, long fledging periods, deferred maturity) which Wynne‐Edwards suggests are adaptations evolved in order to lower the reproductive rate until it balances the mortality, apparently could not be evolved as such; they are more probably adaptations enabling the birds sometimes to raise single chicks in spite of competition for food that makes it impossible to raise more than one. It is considered that variation in the age of first breeding provides an important supplement to variation in reproductive success in regulating the numbers of long‐lived tropical sea‐birds.The possible applications of this hypothesis to sea‐birds breeding in higher latitudes are briefly considered, as are its implications in relation to conservation and exploitation of pop

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1963.tb06766.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY