bluuebunny/crossref_metadata_2025_split huggingface dataset:
INTRASPECIFIC PREDATION AND COLONIAL BREEDING IN LESSER BLACK‐BACKED GULLS LARUS FUSCUS
Authors: Davis J. W. F. , Dunn E. K. 
Published: April 2008

SummaryThe breeding biology of Lesser Black‐backed Gulls was studied on Skokholm Island, Pembrokeshire, where the number of breeding pairs has been increasing at about 20% per annum since 1963. Laying was found to be synchronous within small groups. Clutch size and breeding success showed seasonal declines over the spread of breeding. The loss mainly of eggs, but to a lesser extent of chicks also, caused this overall decline in success. Hide observations indicated that the bulk of these losses arose through predation by nesting adult Lesser Black‐backed Gulls on their nearest neighbours. Not infrequently the protagonist had lost its own clutch shortly before turning predator, and such a chain‐sequence should lead to a steady build‐up of aggressive failed breeders and so account for the observed seasonal increase in egg loss. Attentiveness to the clutch decreased with season but this was unlikely to have been important in precipitating the predation. Intermediate plant cover was associated with highest nest density and also with highest chick survival. In addition, nest density was directly correlated with chick survival. Whether plant cover and nest density separately affect chick production remains unresolved. Nevertheless, the increasing nest densities in this colony caused by the growth of the gull population are thought to be responsible for the widespread intraspecific predation, the intensity of which is probably a new feature of the gulls' breeding behaviour. The implications of this ‘internal’ predation for laying synchrony and aggregated nesting are discussed; these two factors of the breeding pattern probably evolved largely to combat ‘external’ predators. Not only are they no protection against inter‐neighbour predation but appear to facilitate it. It remains to be seen whether this kind of predation will significantly affect breeding patterns with further increases in nest density.
A TWELVE‐MONTH FIELD STUDY OF THE ALDABRAN FODY FOUDIA EMINENTISSIMA ALDABRANA
Authors: Frith C. B. 
Published: April 2008

SummaryThe Aldabran Fody Foudia eminentissima aldabrana was studied for 12 months on West Island, Aldabra atoll. A complete annual cycle was followed in detail in a small population of marked birds, and observations were made on feeding, courtship, breeding and other behaviour. The breeding season coincided closely with the wet season, when insect abundance was highest.Although coconut palms and casuarina trees are both thought to have been introduced into Aldabra by man, the fodies preferred both of these trees as nest‐sites to the native vegetation. It is suggested that this may be a recent preference, resulting from excessive predation by introduced rats Rattas rattus on nests in other sites.In addition to insects and seeds, the Aldabran Fody feeds partly on nectar, and its tongue shows some degree of adaptation to a nectar diet. It is argued that the diversity in bill shape in Foudia cannot be interpreted simply in terms of adaptation for feeding on insects or seeds, but that all three elements in the diet must be considered, in conjunction with the presence or absence of possible competitors.Adult males defend and maintain nesting territories for most of the year. After breeding, they undergo a full moult and assume an eclipse (female‐type) plumage for a variable length of time, regaining the male breeding plumage after a partial prenuptial moult. A small number of males were found to be aberrant, the red in the plumage being replaced by golden yellow. One such bird showed defective territorial behaviour, and four that were dissected Jacked gonads.In almost all ways the behaviour and reproductive patterns of the Aldabran Fody are very similar to those of the Madagascar Fody F. madagascariensis. The latter has been introduced onto many Indian Ocean islands, and in view of its similarities to the Aldabran Fody might well be a serious competitor if it were to be introduced onto Aldabra.
PREDATION AND KLEPTOPARASITISM BY SKUAS IN A SHETLAND SEABIRD COLONY
Authors: Andersson Malte 
Published: April 2008

SummaryFeeding methods and relations of Great Skuas and Arctic Skuas to prey were studied in a seabird colony at Hermaness, Shetland. Great Skuas obtained food by kleptoparasitism, predation and scavenging. They induced Gannets to regurgitate by interfering with their flight; grasping the Gannet by the wing or tail or pushing it down with the feet on its back. Gannets tried to escape by descending to the surface, and regurgitated during 12% of the chases, most frequently when pursued by several birds. Great Skuas caught Puffins by swooping at flocks in the colony. Puffins flying with fish to their young were also chased, releasing food on one fifth of the attacks, or escaping down to the sea and diving. Great Skuas also took Kittiwake nestlings by hovering and grasping the chick with the bill, killing and eating it on the surface. Adult Kittiwakes from nearby nests took to the air, mobbing the predator. More Kittiwakes were engaged in mobbing at unsuccessful than at successful predation attempts, indicating that colonial breeding may be of selective value under such predation. Two different estimates pointed to a Kittiwake nestling predation of 0–12 and 014 young per pair. Fledging success of Kittiwakes was estimated at 0–87‐1‐06 young per pair, considerably lower than at English colonies where predators are absent. In spite of the predation, the Kittiwake colony showed no signs of decrease.Agonistic behaviour and other evidence indicate that Great Skuas defend feeding territories at the seabird colony. Skuas, gulls and Fulmars competed for food at carcasses. Fulmars dominated and chased away skuas.Arctic Skuas deprived Puffins of food. They patrolled the cliff, intercepting Puffins arriving with fish, snatching it from their victim's bill, or inducing them to release fish. Puffins continuing their inward flight lost food more often (30%) than birds descending to the sea (15%)—sometimes diving below. This opportunity to escape may explain the lower success of skuas at Hermaness than at a Puffin colony farther inland from the shore (Grant 1971). Other factors being equal, proximity to the sea may thus reduce the risk of kleptoparasitism.
LIGHT INTENSITY AND THE TIMING OF DAILY ACTIVITY OF FINCHES (FRINGILLIDAE)
Authors: Daan Serge 
Published: April 2008

SummaryThe prevailing general theory of entrainment of endogenous circadian rhythms explains variation in the timing of activity with season, latitude and weather conditions on the basis of the dependence of spontaneous frequency of the rhythm on the intensity of constant illumination. In an experiment designed to test the validity of this theory, Greenfinches and chaffinches were exposed to the natural light‐dark cycle alternately in full illumination and in reduced daylight. Contrary to prediction by current hypotheses for these species, in which the spontaneous frequency decreases with decreasing light intensity, their midpoint of daily activity shifted forward when the intensity of natural daylight was reduced. This result refutes the hypothesis that light affects the timing of activity in nature in a manner predictable from its effect in constant conditions.Both species of finches have a bimodal daily distribution of perch‐hopping activity. The morning peak and evening peak of activity are of about equal strength in winter, but the morning peak increases sharply in the reproductive season. The possibility that the two peaks represent two pacemaker systems, under differential endocrine control, is discussed.The precision in the timing of daily onset and end of activity is positively correlated with the estimated average rate of change of light intensity at these times of day. Thus, day‐to‐day variations are markedly increased in reduced daylight when activity begins late after sunrise and terminates well before sunset.
ADDITIONAL NOTES ON SUBFOSSIL BIRD REMAINS FROM ASCENSION ISLAND
Authors: Olson Storrs L. 
Published: April 2008

SummaryMore extensive collections of subfossil bird bones from Ascension Island in the South Atlantic further confirm that the former seabird populations of the main island were composed of tropical species still present in greatly reduced numbers, mostly on offshore islets. A single specimen of Puffinus lherminieri provides the first fossil evidence of that species from the island. The extinct flightless rail Atlantisia elpenor was the only land bird certainly known to have been native. A femur, apparently from a vagrant individual, is referred to Porphyrula alleni, A specimen of Nycticorax, much smaller than any recent examples of N. nycticorax seen, is either from an unusually small vagrant or possibly indicates an undescribed endemic species.
FOREST BIRDS OF SOUTHWEST NIGERIA
Authors: Elgood J. H. 
Published: April 2008

SummaryThe presence of 191 species, regarded as forest birds, was sought in ten forest reserves of south‐west Nigeria. One of these reserves, Gambari, some 25 miles south of Ibadan, was visited 60 times and the species encountered each visit were noted. From these two series of data estimates of the dispersal and commonness of each species have been made, though not all the 191 species were met during the study.A comparison has been made between the forest birds of southwest Nigeria with those of southeast Nigeria as recorded by Serle (1957).The occurrence of Apalis nigriceps at Sapoba in Mid‐western State and of Parmoptila woodhousei near Lagos are noted as showing a considerable westward extension of their formerly known ranges.
SEASONAL CHANGES IN BODY‐WEIGHT OF OYSTERCATCHERS HAEMATOPUS OSTRALEGUS
Authors: Dare P. J. 
Published: April 2008

SummaryThe body‐weights of Oystercatchers Haematopus ostralegus wintering in Morecambe Bay, north‐west England, showed marked seasonal changes between late summer and late winter, with considerable differences apparent between adult and immature birds. An attempt is made to relate these changes to recorded seasonal variations in prey biomass and to the annual cycles of breeding, moult and migration of the Oystercatcher.The mean weight of females invariably exceeded the mean weight of males in samples collected on the same dates, regardless of age. Adults returned from northern breeding areas in very lean condition, with mean weights ranging from 526 g in males to 540 g in females. Mean weight then increased progressively, due mainly to fat deposition, to a peak in March (up to 662 g in males and 675 g in females) around the time of their main departures for breeding. Heaviest birds then exceeded 800 g. Birds migrating to Iceland in spring would need to be of above average weight in March to make the shortest crossing (850 km, 13 h), via Scotland, while Oystercatchers of 700 g and over could probably make a direct flight (1500 km, 25 h) from Morecambe Bay in favourable weather. Breeding weights of British Oystercatchers were similar to those of post‐breeders returning to Morecambe Bay in late August.The mean weights of first‐year Oystercatchers arriving in August were very low, 449 g in males and 478 g in females. Their weights, and those of second‐ and third‐year immatures, then rose rapidly in autumn, with some fat deposition, and reached mean values ranging between 551 g (males) and 597 g (females) by November‐December. Mean weight then fell by 10–17% from December to March returning close to or below the September levels, whereas adults gained a further 6% during these winter months.Summer and autumn weight gains, and the major moult of adults and older immatures, occurred when the biomass of their two staple mollusc preys, Mytilus edulis (mussel) and Cardium edule (cockle), was maximal. Winter loss in mean weight of immatures corresponded with declining prey biomass, suggesting either that they were less efficient than adults in coping with deteriorating winter food supplies, or that they had no need to accumulate further (premigratory) fat reserves. The autumnal increases in mean weight of immatures are interpreted as an adaptation for withstanding adverse feeding conditions in winter.The Oystercatcher appears to be the only wader species in Britain in which adults increase, rather than lose, weight during the winter. This may be a consequence of an early breeding season, but it may be regarded also as a measure of the success Oystercatchers have achieved by specializing on a difficult but plentiful prey source.
SEASONAL CHANGES IN NECTAR‐FEEDING BY BIRDS AT ZARIA, NIGERIA
Authors: Pettet Antony 
Published: April 2008

SUMMARYNectar‐feeding of birds was recorded during a phenological study of the woody vegetation at Zaria in the Northern Guinea Savanna of Nigeria.Throughout the dry season when it is in a non‐breeding state, the Scarlet‐breasted Sunbird Nectarinia senegalensis concentrates on the ornithophilous plants which flower in an overlapping sequence, and exploits the smaller‐flowered species less frequently. As the flowering of the ornithophilous species decreases at the end of the dry season, the range of other plants exploited increases but, in the early rains as the flowering of the indigenous plants tails off, the sunbird switches to ornamental exotics and the indigenous, shrubby parasite, Tapinanthus globiferus. The bird is more conspicuously insectivorous during the wet season when it breeds. The Pygmy Sunbird Anthreptes platura is a breeding, dry‐season visitor which exploits a somewhat different range of small‐flowered, mainly entomophilous species and some exotics but also takes nectar from those ornithophilous species it can exploit, as well as the chiropterophilous Parkia clappertoniana. The bulk of the breeding population leaves the district before the flowering of the indigenous plant tails off. The five other species of sunbird recorded in the district are either very rare residents or more numerous wet‐season visitors and passage migrants for which records of nectar‐feeding are too few to draw conclusions about seasonal changes but the wet‐season visitors appear to rely on the garden exotics in the comparative absence of flowering indigenous plants.Nectar‐feeding on Bombax costatum and Parkia clappertoniana, where nectar is readily accessible and present in relatively large quantities, was noted for IS species of non‐nectariniid birds, some of which were regular visitors. Some examples of flower consumption probably related to nectar‐feeding are also mentioned.
FACTORS AFFECTING THE AGE OF FIRST BREEDING OF THE KITTIWAKE RISSA TRIDACTYLA
Authors: Wooller R. D. , Coulson J. C. 
Published: April 2008

SUMMARYAt a Kittiwake colony in Northumberland, 80% of those birds which returned to their natal colony to breed were males and these supplied 52% of all male recruits. More females breed away from their natal colony than males. There was no differences in the proportions of young fledged from sites in the centre or at the edge of the colony, or by parents of different experience, which returned to breed. Kittiwakes breed for the first time at ages from 3 to 8 years, but most at 4 or S years old. Males arrive back at the colony at an earlier age than females and breed for the first time one year earlier. Males obtaining sites at the centre of the colony first breed at an earlier age than those at the edges. Neither the age nor the area of first breeding appear to be transmitted from parent to offspring. Males breeding first aged 4 years or younger produced more young than those which first bred aged 5 years or older, despite their partners laying smaller clutches. This difference was most marked among those males recruited to sites in the centre of the colony. The advantage of this earlier breeding is counteracted by a lower survival rate among those males which start to breed at the younger ages. In all breeding Kittiwakes, annual reproductive output increases with experience while annual survival rates decrease. Once they had started to breed, many birds failed to breed in one subsequent season. Nearly 60% of these cases of intermittent breeding occurred in the year following first breeding. Intermittent breeding was most frequent among young birds and among females. It is suggested that each breeding involves a cost to the individual in terms of reduced survival, and that deferred and intermittent breeding are means of guarding survival. A model is proposed whereby the age at which a bird starts to breed, the nesting site which it obtains, and its subsequent breeding strategy result in each individual producing an optimal number of reproducing offspring in its lifetime, relative to its quality.
THE SIGNIFICANCE OF KLEPTOPARASITISM DURING THE BREEDING SEASON IN A COLONY OF ARCTIC SKUAS STERCORARIUS PARASITICUS IN ICELAND
Authors: ARNASON EINAR , GRANT P. R. 
Published: April 2008

SUMMARYBreeding and kleptoparasitism of Arctic Skuas was studied at Vik, Iceland, in 1973. Hatching success was 88.9%; fledging success was 0.27 fledglings per pair. The heavy chick mortality occurred mostly in the first week after hatching. In the early part of the breeding season skuas fed by robbing kittiwakes of their food at sea and by eating arthropods at the breeding grounds. At the time of hatching of skua eggs, which coincided with the hatching of Puffin eggs, skuas switched their feeding activities to kleptoparasitism of Puffins and fish so obtained was the principal item of most skuas' diet thereafter. In the first week post‐hatching, the energy balance of an average adult skua pirating Puffins was estimated to be negative, but changed to positive a week later, although later, coinciding with an influx of non‐breeders it turned back to negative. Arctic Terns which normally breed at Vik, and are exploited by skuas, failed to breed in 1973, and the abnormally heavy chick loss is therefore attributed to this failure of the terns.The success of the skuas kleptoparasitizing Puffins depends on the proximity of the interactions to the cliff or to the ocean, where Puffins seck refuge. Skuas catch fish mostly in the air, especially if it is dropped from high. Fish dropped from low is mostly taken by competing gulls and Ravens, which mostly control the ground and lower airspace. Skuas chasing in groups enhance their success, but the average success per member decreased with group increase. However, the success of the group‐member in the ‘best’ position was equal to that of a single skua. Puffins carry 1 (large)‐6 (smaller) fish, an approximately equal load irrespective of number of fish. Skuas preferentially chase Puffins carrying ‘large’ fish, thus maximizing their yield per effort. Arctic Skuas responded to changes in the numbers of arriving Puffins with a functional response, but their monitoring of the food supply was far from perfect.
ENVIRONMENTAL INFLUENCES ON GROWTH AND SURVIVAL OF NESTLING HOUSE MARTINS DELICHON URBICA
Authors: BRYANT D. M. 
Published: April 2008

SUMMARYGrowth of nestling House Martins was studied in relation to (a) conditions in the external environment and (b) aspects of their breeding biology. The dependence of growth performance on (1) hatchling weights, (2) relative difference in hatchling weights within broods, (3) brood size,(4) season, (5) earliness of breeding in relation to other pairs in the colony, (6) timing of breeding in relation to the median breeding week of the colony and (7) aerial food abundance, was investigated by step‐down multiple regression analysis. Up to the stage of the peak brood weight, early laying, small brood sizes and high hatchling weights were associated with higher nestling growth rates. Large relative differences in hatchling weights however tended to depress mean brood weights and increase weight differences (= size hierarchies) within broods. These differences in hatchling weights were considered to contribute significantly to 23% of all nestling deaths, because small, late hatching nestlings suffered very high mortality even when food was abundant. The nestlings which died showed a progressive reduction on growth rates and all succumbed before the 11th nestling day. Because these differences in hatchling weights can be linked to the food supply during laying rather than immediately prior to their death, it is considered that the mortality of these nestlings can ultimately be attributed to the low quality of eggs from which they hatched.There was a tendency for pre‐hatching factors to diminish in importance throughout growth, while post‐hatching factors increased in importance and, with one exception, were responsible for explaining all the significant variance in the growth characteristics of fledglings. The exception was that differences in wing‐lengths in broods could be linked with weight differences at hatching. Food shortages lowered average brood weights prior to fledging. Because pairs breeding during the median breeding week had lighter young, it was inferred that competition for food during this peak of breeding activity had the effect of lowering nestling growth performance, although the overall effect was considered to be small. Early breeding pairs tended to have larger broods, and these large broods showed a lowered growth performance. However, early breeding pairs had relatively smaller weight and wing‐length differences, in broods of a given size, than occurred in broods of late breeders. It was therefore concluded that early breeding pairs had some attribute which tended to minimize certain disadvantages of large broods. This effect appeared to be linked to the pair, rather than to season or food supply.
THE FORMATION, STRUCTURE AND FUNCTION OF MIXED‐SPECIES INSECTIVOROUS BIRD FLOCKS IN WEST AFRICAN SAVANNA WOODLAND
Authors: GREIG‐SMITH P. W. 
Published: April 2008

SUMMARYMixed‐species flocks of birds were observed during the wet season (July to September 1975) in savanna woodland in Ghana. Thirty‐four flocks contained birds of 56 species in 20 families, including insectivorous, granivorous, and nectarivorous species, using a wide range of foraging methods. Only two species occurred in more than half the flocks. There was no correlation between the number of flocks joined by a species and its abundance in the community.Among insectivores, but not granivores, the species which joined most flocks were those which habitually occurred in the largest single‐species groups. All stages of breeding activity were represented by the various members. Some species joined flocks only while these were passing through their territories.Of the two species which were present most frequently, there were no differences between mixed and single‐species flocks for Eremomela pusilla, but Parus leucomelas foraged and called on more occasions in mixed flocks than single‐species flocks, though the rates of foraging and calling were related only to the number of P. leucomelas present.Groups of P. leucomelas appeared to initiate some flocks by attraction due to their conspicuous wing‐bars, active movement, and loud calls. Black‐and‐white species joined them first, followed by birds of other plumage patterns.The advantages of mixed flocking are thought to be connected with finding patches of the food of bark‐ and foliage‐searching insectivores, which were the only species regularly seen foraging in the flocks. Because of dry season burning which leaves small unburnt patches of savanna, these insect species may share a common, patchy distribution. Birds may also gain protection from predators, and some species probably gain no advantages.The species composition and behaviour of flocks previously recorded elsewhere in African savannas are similar to the Ghana flocks.