摘要:

SummaryBetween 1963 and 1965 three expeditions have investigated the autumn migration of raptors and storks, on two occasions in southeast Turkey, and once in Lebanon.Nearly all the soaring birds leaving Europe by the Bosphorus cross Asia Minor and turn south at the Gulf of Iskenderun. The commonest of these migrants are White StorkCiconia ciconia, Honey BuzzardPernis apivorus, and EaglesAquilaspp.Other species such as Common BuzzardButeo buteoare not usually seen crossing the Bosphorus, but occur in large numbers in the flocks seen south of the Gulf of Iskenderun. It is suggested that these are birds from Russia and north Turkey. Common Buzzards also occur on Cyprus in autumn, but their point of origin is not clear. Short‐toed EaglesCircuetus gullicusand vultures join the migration from their breeding grounds in Turkey and the Levant.Different species tend to migrate at different times of year. White Storks, Egyptian VulturesNeophron percnopterusand Black KitesMilvus migrunsmove chiefly between late August and mid‐September, while eaglesAquiluspp. start in late September and continue until November. Other species are intermediate, or spread their migration out over a longer period.The volume of migration at different times of day is discussed. No general conclusions are possible but in 1964 a correlation was obtained between cloud cover and the start of the migrat

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1967.tb00018.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

SummaryThis paper describes the results of investigations into the factors affecting breeding success of the Herring and Lesser Black‐backed GullsLarus argentatusandL. fuscus, in the large colony on Walney Island, northwest Lancashire, between 1962 and 1965. These investigations were concerned with the incubation period, and the first ten days after hatching.The survival of chicks to ten days is 67% in Herring Gulls, and 56% in Lesser Black‐backs. Most of these losses occur in the period just after hatching and are due to “cannibalism” by other gulls. This form of predation does not appear to be masking any effects from starvation or disease.The following factors contribute to egg or chick mortality:breeding too late (and, to a much smaller extent, too early); breeding in the open, as opposed to amongst cover; the facts that eggs in small clutches have a lower hatching success than those in large ones and that Herring Gull (but not Lesser Black‐back) chicks in small broods are less likely to survive to ten days than are those in large broods.Chick mortality after the first ten days is not certainly known. About 30% of the eggs laid gave rise to fledged young— or about one fledged chick per pair.In the Herring Gull, the average clutch size (2.56) is lower than that of the Lesser Black‐back (2.76). Both species show a seasonal decline in clutch size—this occurs earlier in the Herring Gulls than in the Lesser Black‐backs.The Walney population, which stood at about 700 pairs in 1950, had reached 12,000 in 1957, and is at present about 18–19,000 pairs. It is suggested that this increase may be linked to the greater availability, or exploitation, of human garbage in the Morecambe Bay area. The population explosion between 1950 and 1957 must have been partly due to massive immigration and could not have come about through natural increase alone.The possible influences of the gulls' behaviour on the population growth are discussed. There is no evidence of any “shock disease”, although the Walney colony is very crowded. “Cannibalism” is regarded, not as evidence of a failing food supply, but as an extension of the normal hunting behaviour of these omnivorous gulls; it will be an economical means of obtaining food only in a large, dense colony, such as Walney. It may be offset by increased breeding effic

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1967.tb00019.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1967.tb00020.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1967.tb00021.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

SummaryObservations are given for 25 species of birds seen in southwestern Ecuador or just offshore near the mouth of the Gulf of Guayaquil to supplement the records of Marchant (1958) and Lévêque (1964). Of the 25 species listed, 19 are sea‐birds and a number are species not commonly reported from the area. Two records of the Antarctic FulmarFulmarus glacbloidesare given, one of which may be the first for Ecuador. The presence of Sooty TernsSterna fuscataand possibly a few Brown BoobiesSula leucogasterjust north of the Santa Elena Peninsula is unusual and was probably the result of an incursion of warm water from the west or north. In May 1966 450 + boobies, 10 Sooty Terns and 350 Brown Pelicans were counted on Isla Pelado (El Viejo) in Bahia de Santa El

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1967.tb00022.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

SummaryBirds which build the simplest and scantiest nests use a single movement, sideways‐throwing, in assembling material; and a modified form of it, sideways‐building, in arranging material on the site. Sideways‐throwing is usually performed by a standing or walking bird which picks up a small object in front of it, and throws it back, either to one side or beneath it, with a sharp sideways movement of the head. Sideways‐building is normally performed by a sitting bird which takes material and deliberately places it to either side or in towards its breast. Sideways‐throwing and sideways‐building occur in the Struthionidae, Rheidae, Dromaiidae, Gaviformes, Procellariformes, Anseriformes, Meleagrididae, Phasianidae, Gruidae and Charadrüformes. Sideways‐building only is recorded in the Sulidae ahd, forPlatalea leucorodia, in the Threskiornithidae. There are no records of nest‐building in the Apterigidae, Tinamidae, Otidae, and Pteroclididae.Sideways‐throwing occurs within the vicinity of the nest‐site, often in conjunction with conflict behaviour; and typically occurs at nest‐relief, performed by the bird leaving the nest. This results in material accumulating at the nest‐site, and this may be pulled in by the sitting bird during sideways‐building, The amount and type of material depends on its availability around the nest‐site. In species where only one sex incubates the sitting bird may leave the nest at intervals and perform sideways‐throwing.Sideways‐throwing appears to occur frequently as a form of irrelevant behaviour, usually in agonistic situations; sideways‐building often occurs when a sitting bird is disturbed. Since sideways‐throwing is a relatively ineffectual form of nest‐building, the creation of a nest appears to depend on the extent to which the bird finds itself in a conflict situation and the amount of material near the nest. It seems possible that it may have evolved as Irrelevant Behaviour rather than true nest‐building. It is suggested that the movements might be derived from false‐feeding movements involving the picking up of inedible objects, and from the flick of the head, with which a bird removes an unwanted object adhering to its bill. Such behaviour performed by a bird walking repeatedly from the nest could result in the accumulation of material at a nest‐scrape. Relatively little modification would be needed to create a form of nest‐building suitable for very simple nests.Chance sideways‐throwing seems to occur in many species. Nests in damp situations may be larger than those in dryer ones and, although this might be accidental, the behaviour of some species during floods suggests purposeful building. Some species appear to align their throwing in relation to the position of the nest. In some groups within the Charadrüformes sideways‐throwing appears to have been replaced by the carrying of material to the nest. In such species relict sideways‐throwing often occurs when material is deposited on the nest‐site; and sideways‐building is used in the arrangement of the material. It is possible that movements similar to sideways‐building used in nest construction by birds in other groups might be homologous with it an

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1967.tb00023.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

SummaryFive cases of interbreeding between the Red‐billed GullLarus novaehollandiae scopulinusand the Black‐billed GullL. bulleriin the wild in New Zealand are described. Captive hybrids from the wild population were shown to be fertile. Comparison between two years' observations in the same colony suggests that interbreeding occurs only when isolated individuals with a strong readiness to mate are prevented from mating with conspecifics. Other cases of interbreeding inLawsspp. support this conclus

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1967.tb00024.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

SummaryIn the southwestern part of the Kalahari region, the Double‐banded CourserRhinoptilus africanusis restricted to stony terrain with low vegetation and good visibility. Nests are always exposed, usually on flat ground, less often in hollows or slopes, and seldom on rises. Sixty per cent of nests were among mammal droppings.Nest relief is rapid and occurs every two hours or so; side‐throwing of small objects around the nest by the relieved bird is part of the ceremony. Incubation of the single egg takes about 26 days. The newly‐hatched chick is weak and is fed exclusively by the parents for the first few days. It can fly at about six weeks of age. Breeding seems to be continuous, regardless of weather and season.The calls, displays, comfort movements and ritualized intention movements are described and analysed as far as possible. Adult coursers are subjected to an intense heat load in summer, and have a number of behavioural heat‐loss mechanisms which are described and discussed.R. africanusandCursorius rufus(both common coursers of the Kalahari) are briefly c

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1967.tb00025.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

SummaryThe process of cranial pneumatization in the Zebra FinchTaeniopygia castanotisis substantially similar to that described in the House SparrowPasser domesticus, but is completed somewhat earlier. Full pneumatization of the cranium is usually attained between 138 and 153 days from hatching, though in some birds it may be retarded. A series of diagrams, representing 41 stages in the process, enables the ages of young birds to be established.

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1967.tb00026.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

SummarySome biologists have held that the rate of reproduction in birds tends to be adjusted to the average annual mortality; others, that it is limited only by the parents' ability to raise sturdy young. The latter theory, that of maximum reproduction, is likely to be true only if three related propositions are true:(1) that an increase of clutch size is more likely to occur than some other mutation affecting the rate of reproduction; (2) that a genotype with a wastefully high rate of reproduction can supplant a genotype with a more conservative but adequate rate; and (3) that an excessive rate of reproduction is not harmful to the species. None of these assumptions has been proved.In a population not obliged to employ its full reproductive potential to maintain itself at a favourable level, mutations which limit this potential may arise and persist. They may effect this limitation by means of:(i) reduction in clutch size; (ii) reduction in the number of broods; (iii) failure of the male to attend the nest, often followed by failure to form pairs; (iv) deferment of reproductive maturity; (v) developments in territorialism that limit the number of nesting birds or the number of progeny they can rear; (vi) restriction of nesting to traditional sites; and (vii) the time‐consuming construction of elaborate nests. These limitations of the rate of reproduction must be regarded as adaptive because, like other adaptations, they adjust the birds more perfectly to the conditions in which they live and reduce the stress to which they are subjected.In both tropical and temperate regions, species in which only the female feeds the nestlings have broods as large as species in which both parents feed them. It follows that the two parents are not rearing as many young as they could nourish.The view that hole‐nesting birds can rear larger broods than open‐nesters because their young develop more slowly, and require less food per capita per day, is untenable. Nestlings raised in holes and burrows gain weight about as rapidly as those in more exposed nests, but for safety they remain longer in their protected abodes. The larger broods of hole‐nesters evidently compensate for the difficulty of obtaining nest sites, which delays the breeding of some pairs and prevents that of others.Clutch size is by no means closely adjusted to the number of young the parents can raise. If given additional nestlings, some birds attend them adequately. In other species, young are rarely fledged from all the eggs. In many cases, asynchronous hatching is not, as has been claimed, an arrangement which permits the parents to adjust to a varying food supply the number of young that they rear. In many raptors, fratricide and cannibalism reduce the size of the brood, sometimes to a single nestling, regardless of the abundance of food.The more stable the environment, the more closely the reproductive rate tends to be adjusted to the mortality; the more a population is subject to catastrophic reductions, the more the rate will approach the maximum.Primarily, the reproductive rate is controlled by heritable characters, which can adjust the rate to a stable environment but rarely respond to short‐term fluctuations in external conditions or population density. The last fine adjustment of a population to its habitat is effected by processes that are density‐dependent:either density‐dependent regulation of the reproductive effort, or density‐dependent mortality of adults or young, or a combination of the two.The general evolutionary trend in the Metazoa is toward producing fewer offspring and taking better care of them. This would hardly be possible if the more prolific genotype always prevails over those which raise smaller families and in consequence can attend their young somewhat better. The regulation of the rate of reproduction is a unique evolutionary problem, because a mutation conferring greater fertility, although often detrimental to the species, tends to diffuse through it as no other harmful mutation can. Yet it is counteracted by many factors, chiefly ecological, which operate subtly and are more difficult to appreciate than the f

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1967.tb00027.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY