bluuebunny/crossref_metadata_2025_split huggingface dataset:
TIMING AND SPACING OF BROODS IN THE BLACK‐HEADED GULL LARUS RIDIBUNDUS
Authors: Patterson I. J. 
Published: April 2008

SUMMARYThe nests of the Black‐headed Gull Larus ridibundus are closely aggregated into dense colonies and their use synchronized, these two phenomena together tending to produce a maximal clumping effect. Within such a colony however, nests were found to be spaced out to produce a non‐random uniform distribution. The commonest distance between neighbouring nests was found to be about one metre, in contrast to related species. This study was concerned with two aspects of this distribution pattern; its survival value and its behavioural causation.It was found that pairs nesting just outside the colony had a much lower breeding success than those nesting in the colony and that nests on the colony fringe had a slightly lower success than those in the centre. Pairs laying during the peak laying period had a higher breeding success than pairs laying either earlier or later in the season. Since by far the most important mortality agent was predation, it seems likely that both clustering and synchronization of nesting function as antipredator systems and arguments in favour of this are discussed.Variations in nest‐spacing within the colony were not correlated with variations in breeding success.In the causation of the spacing between nests, territorial aggression was demonstrated to be an effective dispersion mechanism and the way in which this mechanism works was investigated in detail.This spacing mechanism was not sufficient by itself to explain the observed densities, which were higher than one would expect from the aggression alone; there was also some tendency for birds establishing a new nest‐site to cluster close to others. The interaction between this, the territorial aggression of the residents and the subsequent avoidance responses of the settling birds, can explain the nest spacing pattern and probably also the observed densities.
ON THE BIRDS OF MOROCCO
Authors: Smith K. D. 
Published: April 2008

SUMMARYFifteen months were spent in Morocco. A few ecological aspects of the country are described, together with their influence on the dispersal of birds in winter. Some winter visitors are listed and discussed, several species were much commoner in the winter of 1962/63 than in 1963/64, in some cases presumably as a result of the cold weather in Europe, although in others not obviously so. Cold‐weather movements of gulls, Lapwings and Cranes were observed. Individuals of species that are normally trans‐Saharan migrants winter in Morocco in small numbers. Spring migration in southeast Morocco is excluded from discussion, but autumn migration in western Morocco is summarized and compared with existing data. The systematic list is devoted largely to winter visitors and passage migrants, but resident species are listed when new localities, breeding data or field notes warrant their inclusion. Six species not hitherto recorded in Morocco, were seen.
THE FOOD AND FEEDING HABITS OF SHELDUCK TADORNA TADORNA
Authors: Olney P. J. S. 
Published: April 2008

SUMMARYThe food and feeding habits of Shelduck Tadorna tadorna are described, based on the analyses of the viscera of 30 birds collected under special licence, and of 18 birds found dead or dying during the cold weather of 1963, on faecal material from eight incubating birds, on field observations and on the literature. The birds came from a number of different localities and from each month of the year, apart from July.The mollusc Hydrobia ulvae (Pennant) was found in all 46 birds which contained food, and it is quite obvious, and this is confirmed by the literature and by faecal analyses, that this is the most important food item during much of the year and in many different localities. Other species eaten included the bivalve Macoma balthica, the amphipod Corophium volutator, the ragworm Nereis sp., the alga Enteromorpha, and occasionally the seeds of various plants.The importance of H. ulvae is examined in the light of its distribution and numbers, which may be a strong controlling factor in concentrating Shelduck in certain areas at certain times of the year.The feeding behaviour of Shelduck, and a number of other birds, is apparently closely related to the cyclic behaviour pattern of the main food species, H. ulvae.It seems that Shelduck have a rather fixed type of feeding behaviour which exploits only one feeding niche and therein mainly one food item. Any event (prolonged gales or very cold weather) which prevents the bird from using that niche can be the cause of heavy mortality.
NOTES ON SOME RESIDENT BREEDING BIRDS OF SOUTHWEST KENYA
Authors: Betts F. N. 
Published: April 2008

SUMMARYA description is given of the topography and climate of the Narok district of S.W. Kenya. The rainfall and its effect on the breeding of birds is discussed. A list is given of the avian biotopes of the district followed by a systematic list of breeding species with dates of breeding and altitudinal range of residence.
THE MOULT OF THE BULLFINCH PYRRHULA PYRRHULA
Authors: Newton I. 
Published: April 2008

SUMMARYThe distribution of feather tracts and their sequence of moult in the Bullfinch is described. The adult post‐nuptial moult, which is complete, lasted 10–12 weeks, and the post‐juvenile moult, which is partial, 7–9 weeks. Adult moult began with the shedding of the first (innermost) primary and ended with the replacement of the last. Variations in the rate of moult in the flight feathers were mainly achieved, not by changes in the growth rates of individual feathers, but in the number of feathers growing concurrently. The primaries were shed more slowly, and the onset of body moult delayed, in birds which were still feeding late young.In 1962, the onset of moult in the adults was spread over 11 weeks from thc end of July to the beginning of October, and in the two following years over the six weeks, from the end of July to the beginning of September. The onset of moult was delayed by late breeding, which itself occurred in response to a comparative abundance of food in late summer, markedly in 1962. In all years, the first juveniles to moult started at the end of July, and the last, three weeks after the latest adults. Juveniles moulting late in the season retained more juvenile feathers than those moulting earlier.During moult, adult and juvenile Bullfinches produce feathers equivalent to 40% and 33% respectively of their dry weights. In both, for much of the moult, an average of nearly 40 mgm. of feather material—some 0.6% of their dry‐weight–is laid down each day. The remiges of the adult comprise only a seventh of the weight of the entire plumage, and it is suggested that their protracted moult results not so much from their energy requirements, as from the need to maintain efficient flight. Variation in the rate of moult in the remiges was much less pronounced than in the body feathers. Bullfinches were less active during moult than at other times of the year. The weights of both adults and juveniles increased during moult.The food during the moult period is described. In all years, most Bullfinches finished moulting just before food became scarce, even though this occurred at different times in different years. In one year, adults moulting latest in the season probably survived less well than those moulting earlier; the same was apparently true of the juveniles in all years. The timing of moult in the Bullfinch, and the factors initiating it, are discussed in relation to the breeding season and foodsupply near Oxford.
FURTHER EXPERIMENTS ON DISTANCE NAVIGATION IN THE ADELIE PENGUIN PYGOSCELZS ADELZAE
Authors: Penney R. L. , Emlen J. T. 
Published: April 2008

SummaryFurther experiments confirm our recently reported findings that Adelie Penguins Pygoscelis adeliae, transported from rookeries on the coasts of Antarctica to remote release points, consistently select a departure direction to the N.N.E. with respect to their home meridian. New releases were made at the South Pole where sun altitude is constant and in the offshore pack ice where the initial N.N.E. departure direction led the birds directly away from their home.Birds imported from the Mirnyy coast, 85° of longitude to the west of Cape Crozier selected a departure direction to the N.W. After being held in an open pen at the new position for three weeks, however, Mirnyy birds revised their orientation to match the N.N.E. departures of a comparably held group of Crozier birds.Juvenile penguins taken from creches and from the beach at Cape Crozier selected the same departure direction as adults.Several lines of evidence suggest that the mechanism used in initial direction selection may be different from that used in course maintenance.The consistent northward or outward departure orientation is discussed in terms of escape to offshore feeding grounds. The easterly component of this orientation is discussed in terms of compensation for a westward drift imposed on outward‐moving birds by coastal currents. A circadian rhythm in phase with conditions at the longitude of the home rookery is regarded as serving to guide a displaced bird back to its home coast. A circadian rhythm reset to the solar cycle of a new longitude is regarded as serving to guide a displaced bird to the nearest coast.The return of displaced birds to their home rookery, after initial orientation in other directions, emphasizes the fact that the departure response observed in these studies is only one part of a complex navigational mechanism, which guides the Adelie Penguin through its seasonal migrations.
THE MIGRATION OF RAPTORS AND STORKS THROUGH THE NEAR EAST IN AUTUMN
Authors: Cameron R. A. D. , Cornwallis L. , Percival M. J. L. , Sinclair A. R. E. 
Published: April 2008

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 Stork Ciconia ciconia, Honey Buzzard Pernis apivorus, and Eagles Aquila spp.Other species such as Common Buzzard Buteo buteo are 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 Eagles Circuetus gullicus and 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 Vultures Neophron percnopterus and Black Kites Milvus migruns move chiefly between late August and mid‐September, while eagles Aquilu spp. 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 migration.
BREEDING SUCCESS AND POPULATION GROWTH IN A COLONY OF HERRING AND LESSER BLACK‐BACKED GULLS LARUS ARGENTATUS AND L. FUSCUS
Authors: Brown R. G. B. 
Published: April 2008

SummaryThis paper describes the results of investigations into the factors affecting breeding success of the Herring and Lesser Black‐backed Gulls Larus argentatus and L. 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 efficiency due to social factors.
INTERBREEDING OF LARUS NOVAEHOLLANDIAE SCOPULINUS AND LARUS BULLERI IN THE WILD IN NEW ZEALAND
Authors: Gurr L. 
Published: April 2008

SummaryFive cases of interbreeding between the Red‐billed Gull Larus novaehollandiae scopulinus and the Black‐billed Gull L. bulleri in 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 in Laws spp. support this conclusion.
FEEDING BEHAVIOUR AND DMNG RHYTHMS OF SOME NEW ZEALAND SHAGS, PHALACROCORACIDAE
Authors: Stonehouse Bernard 
Published: April 2008

SummaryRecords of the duration of the dives and resting periods of two species of Shags, which fish in the coastal waters of New Zealand's South Island, show the existence of an ecological segregation whereby each species is working within the limits of its greatest physiological efficiency. The smaller species hunts only in shallow water, the larger maintains efficient dive/rest ratios in deeper off‐shore water.
BIOLOGY OF THE IMMIGRANT CATTLE EGRET ARDEOLA IBIS IN GUYANA, SOUTH AMERICA
Authors: Lowe‐McConnell Rosemary H. 
Published: April 2008

SummaryThe success of the immigrant Cattle Egret Ardeola ibis in Guyana appears to be due mainly to its breeding biology, combined with man's activities in clearing and draining land for stock and by his selective shioting.Long.‐established heronries are beine taken over bv the Cattle Egret. In Aurmst 1959 during the principal nesting season in the main rains 90% of the 1786 heron nests in the Botanic Gardens Georgetown, belonged to Cattle Egrets, the others to Little Blue Herons Hydranassa caerutea, Black‐crowned Night Herons Nycticorac nycticorux, Snowy Egrets Egretta thula, Tricolour Herons Hydranassu tricolor, and Streaked Herons Butorides striatus. In the December rains the same year another 1700 Cattle Egret nests were in use here, but no indigenous herons were nesting. These were, however, joined in January by Black‐crowned Night Herons, Snowy Egrets, Little Blue and Tricolour Herons.In addition to having two peak nesting periods a year, instead of one as the indigenous herons generally have, the Cattle Egrets react faster to the onset of the rains and obtain the best nest‐sites, and they are helped by the tendency of the indigenous herons to display more aggressively against their own species than against the intruder; also now that Cattle Egret numbers are high they can find mates very rapidly. Both indigenous herons and Cattle Egrets have one to three young per brood in Guyana, and the nesting period lasts about two months.The peak nesting time varies from year to year with the advent of the rains. Nesting appears to be stimulated by, and its success related to, rainfall. A cycle of wet years in Guyana preceded the arrival of the Cattle Egrets in North America in 1952. In Guyana their dispersal inland was restricted, probably by the forest, until 1961.
THE BIOLOGY OF OYSTERCATCHERS HAEMATOPUS OSTRALEGUS ON SKOKHOLM ISLAND, S. WALES
Authors: Harris M. P. 
Published: April 2008

SummaryA population of about 50 pairs of Oystercatchers Haematopus ostralegus nesting on Skokholm Island, S. Wales, was studied between 1963 and 1965. Other information on Skokholm Oyster‐catchers over the last 25 years was also analysed.The adults were trapped, colour‐banded and sexed by bill measurements. With few exceptions, birds kept the same mates and territories from one season to the next. Apparently the male is responsible for retaining the territory. Some Oystercatchers breed at three years but most do not do so until four or five. It seems that there is a high population pressure, preventing young birds from establishing themselves. The annual adult survival in the two years was 88% and 90% respectively.The average clutch‐size on Skokholm is known for many years, and varied annually between 2.5 and 3.3. The number of c/4 varied greatly from year to year. There was a seasonal decline in mean clutch‐size and also in egg and nest success. Predation, especially by Lesser Black‐backed Gulls, was the main cause of egg loss.In 1963, 36.7% of hatched chicks fledged and 59% in 1964. The larger clutches were more successful and produced more surviving young than did the more numerous smaller clutches. Early hatched young are more successful than later young.The average yearly mortality of birds between fledging and breeding was 40%.
THE DELAY IN OVULATION PRODUCED BY pp'‐DDT AND ITS POSSIBLE SIGNIFICANCE IN THE FIELD
Authors: Jefferies D. J. 
Published: April 2008

SummaryA significant correlation between pp'‐DDT intake by the female Bengalese Finch Lonchuro striata and delay in ovulation is reported. Linked with earlier work showing that pp'‐DDT can cause inhibition of the testicular growth and secondary sexual characters of cockerels, it is deduced that in this context the site of action of the pp'‐DDT is probably the pituitary or hypothalamus. Inhibition of the secretion of the pituitary hormones could explain the reported recent increase in egg breakages by predatory birds. It is also probable that organochlorine pesticides are responsible for the late breeding of several species of birds reported in the early nineteen‐sixties. This could affect a population in that large sublethal doses which double the time for egg laying could cause a double‐brooded bird to be out of phase with the food supply for the late broods.
PHOTORESPONSES OF THE WOODPIGEON COLUMBA PALUMBUS IN RELATION TO THE BREEDING SEASON
Authors: Lofts B. , Murton R. K. , Westwood N. J. 
Published: April 2008

Summary

The gametogenetic response following photo‐stimulation was tested in Woodpigeons under controlled laboratory and aviary conditions. Subjects were wild‐caught adult or first‐winter birds or were hand‐reared from wild‐taken nestlings. The natural seasonal gonad cycle is described and experiments were related to this cycle.
Gonad recrudescence could be initiated in adults with regressed organs by exposure to summer photoperiods, while the normal vernal recrudescence could be prevented if birds were artificially kept on short (winter) daylengths. Thus Woodpigeons could be stimulated towards reproductive condition at seasons when the gonads of wild‐living birds remained inactive, viz. late September to mid‐February.
Juvenile males were unresponsive to extra photo‐stimulation until they were about six months old. This meant that some spermatogonial division could be procured in a few individuals in late February, but juveniles were not very noticeably affected by an extended photoperiod until mid‐late March. This is the time when juveniles first begin gametogenetic development in the wild, though spermatogenesis normally accelerates in April after which time the rate of gonad development is constant. First‐winter females were judged to resemble males in their photoperiodic responses but the sample examined was small.
The results confirm that the natural gonad cycle in the Woodpigeon is controlled (via gonadotrophic hormones) by seasonal changes in daylength. More important is the finding that the species appears to possess no post‐nuptial refractory period. Thus, at the end of the breeding season in September birds kept on summer daylengths were maintained in full reproductive condition until December. The testes of controls placed on winter daylengths regressed within one month, but they were immediately responsive to a summer daylength which stimulated spermatogenesis within a month.
The discussion argues that the avian refractory period is not a necessary period for gonad rehabihtation and reorganization and that it has not evolved as a fixed period serving to time the breeding season; views which until now have been current. Instead, it functions only as a safety mechanism, preventing unseasonal reproduction in those species for which natural selection favours seasonal breeding. In such species the evolution of sensitivity to a particular daylength could result in breeding taking place at the wrong time, for example spring responding species might also respond in the autumn. Because natural selection permits Woodpigeons to remain in breeding condition from March until September, without disadvantage, a direct response to natural daylength can regulate the cycle, and there is no need for a period of pituitary refractoriness. It is not known if some pigeons have lost the refractory period or whether they never possessed one.
SPRING MIGRATION AT THE BOSPHORUS
Authors: Collmait J. R. , Croxall J. P. 
Published: April 2008

SummaryDuring observations made at the Bosphorus from 23 March to 6 April 1965, 3473 raptors were seen; the majority were Spotted/Lesser Spotted Eagles and Honey Buzzards. The migration of the main species is considered in some detail and attempts are made to correlate this with the prevailing weather. Comparisons are made with the records of observers both in spring and autumn at the Bosphorus and in spring at Gibraltar. Honey Buzzards pass in spring a month later at Gibraltar than at the Bosphorus. It is suggested that this is related to the timing of spring in the breeding areas to which these birds are returning. Notes on the observations of passerine movements and a night migration of Black Storks are also included.