bluuebunny/crossref_metadata_2025 huggingface dataset:
BREEDING OF THE WHITE‐BACKED AND RÜPPELL'S GRIFFON VULTURES, GYPS AFRICANUS AND G. RUEPPELLII
Authors: Houston D. C.
Published: April 2008

The breeding season of two species of griffon vultures are described. Rüppell's Griffon Vulture lays 2–3 months earlier than the White‐backed Griffon. Young birds were hand‐reared to determine their food requirements during growth; these estimates were combined with the food requirements of adult birds to make an estimate of the amount of food a parent bird needs to obtain when it is rearing young. The amount of food actually obtained by a group of birds was recorded from the size of the crops of birds returning to the breeding colony in the afternoon. The comparison of the estimates of the food obtained and the food required through the breeding season suggested that there may be a period during rearing when there was insufficient food available to satisfy the food requirements of both chick and adult. Chicks were found to have a very high survival rate and were probably receiving sufficient food. Presumably adult birds were not therefore receiving sufficient food, and the examination of a sample of adult birds for body condition through the breeding season showed a clear decline in their fat deposits. It was considered that in both species, breeding was timed so that the young left the nest at a period in the year when food conditions were good and the young birds could feed with little competition from adults. The parent birds therefore had to rear young during a season in the year when food conditions were not always adequate and they had to rely on utilising fat reserves. The food conditions for vultures during this study were probably favourable and during years of food shortage breeding may become impossible, or restricted to the most aggressive and dominant individuals.
AUTUMN MIGRATION OVER PUERTO RICO AND THE WESTERN ATLANTIC: A RADAR STUDY
Authors: Richardson W. John
Published: April 2008

Migration over Puerto Rico was recorded by time‐lapse filming of the display of a long‐range surveillance radar on 108 days and 93 nights in the period 13 August‐13 November in 1970 and 1971. Altitudes were recorded on nine days.

Passerine movements to the E‐SSE from Puerto Rico and Hispaniola occurred on many nights. Their density was greatest between late September and mid‐November, especially when the easterly Trade Winds abated. Shorebirds and passerines moving SE, S and SW on a broad front approached from over the ocean intermittently throughout the period, with largest numbers from mid‐September to early November. Arrivals occurred at all hours of the day and night. Many were at altitudes of 3 to 6 km, including some believed to be passerines. Birds that flew high by day descended after sunset. Many continued southwards over or past Puerto Rico.

The tracks of birds arriving from over the ocean were correlated with wind direction, but were rarely downwind. The variance in tracks was slightly greater on cloudy than on clear nights, but there was no evidence of serious disorientation in any situation. There was a negative correlation between the density of arrival from the north and the easterly component of the wind. This, together with evidence that the eastern edge of most passerine flights was near Puerto Rico, suggests the existence of lateral wind drift. The relationships of estimated headings to wind and to tracks also suggested that the birds were drifted, contrary to the situation in spring.

The shorebirds and passerines arriving from the NW‐NE were concluding overwater flights of 2000–3000 km from SE Canada and the eastern U.S.A., often along clockwise‐curved routes. Some that continued to South America flew 4000 km or more non‐stop.
THE COMPOSITION AND BEHAVIOUR OF SOME MIXED‐SPECIES BIRD FLOCKS IN SARAWAK
Authors: Croxall J. P.
Published: April 2008

Mixed‐species flocks of birds feeding on insects were observed mainly in forest in Sarawak at a time of year when insect availability is known to be near its annual minimum. The approximate individual and specific composition of most flocks were noted. Twenty‐six species occurring in 25% of flocks were regarded as occasional members, 15 species occurring in 40% of flocks being classed as regular members.

Recording species' feeding behaviour was the main priority and few observations of inter‐ and intra‐specific interactions within the flock, horizontal distribution or vertical stratification were made, although the last proved to be of potential significance. From the analysis of feeding behaviour two groups of species were distinguished. The larger group contained those usually having an exclusive common feeding pattern and showing very little overlap with the other such species. Fewer species used a wide range of feeding methods, all of which were shared with other species, but the least overlap was with other members of the same category.

The observed composition of these flocks, in terms of regular members, might be interpreted as ensuring a low level of inter‐specific competition and it is suggested that the less specialized foragers may occur in the flocks by utilizing the ‘gaps’ between, and absences of, specialists.

The possible advantages of membership of mixed‐species flocks are briefly considered and the likelihood of the selective advantage in any situation being the result of a balance of factors emphasized. In the apparent absence of regular potential predators the existence of these flocks is interpreted primarily as an adaptation for augmenting available insect food, particularly perhaps at critical times of year, by flushing insects as a result of the foraging activities of flock members. It is suggested that the varied responses of insects on being disturbed coupled with the different and fairly specialized feeding techniques of the birds could ensure benefit for all members of the flock.
THE FOOD OF RED GROUSE CHICKS LAGOPUS L. SCOTICUS
Authors: Savory C. J.
Published: April 2008

The diet of young Red Grouse was studied from the crop contents of 211 chicks caught on a moor in northeast Scotland. The food was more varied than that of adults, but shoot tips of heather usually formed at least 75% (by dry weight) of their diet, as in adults. Arthropods, particularly Diptera, were taken frequently by chicks up to three weeks old, but they formed less than 5% (by dry weight) of the diet then. The chicks ate more invertebrates when more were available. There was no evidence that chick survival was related to the abundance of invertebrates. The chicks ate heather containing more nitrogen and phosphorus than that eaten by adults at the same time of year.
THE ABILITY OF BARN OWLS TYTO ALBA TO DISCRIMINATE AND LOCALIZE AVIAN ALARM CALLS
Authors: Shalter Michael D. , Schleidt Wolfgang M.
Published: April 2008

Ten Barn Owls were tested in a sound‐room with recordings of various alarm calls and noise. The owls readily responded with head movements to the majority of stimuli and correctly oriented to their source. The seeet alarm call and the ‘warning’ call elicited the least responses, but they were properly localized by all owls which did respond. This suggests that rather than non‐localizability accounting for the fewer observed responses to the seeet and ‘warning’ calls, there is either something else in the quality of those sounds, or in the manner in which they are processed by the bird, which does not elicit responses to the degree that transient sounds with broad frequencies do. Selection in these predators for non‐responsiveness is suggested as a counter‐strategy to minimize futile energy expenditure in attacking, or otherwise responding to an alerted prey.

An additional hypothesis, consistent with Darwin's antithesis principle, is proposed whereby intraspecific and interspecific selection, rather than predator selection for non‐localizability, has led to the evolution of seeet and mobbing calls.
A RADAR STUDY OF TERN MOVEMENTS ALONG THE COAST OF GHANA
Authors: Grimes L. G.
Published: April 2008

During spring and autumn 1970 and 1971 the movements of terns off the coast of Ghana near Accra were studied by radar. In autumn, dense movements were recorded within 22 km of the coast both day and night from July to early December. Fluctuations in the magnitude of the movements suggest that the terns were on passage through the Gulf of Guinea. Simultaneous to these movements were roosting flights into shore roosts and both movements appeared independent.

In contrast, no spring movements along the coastline were detected either by radar or visually from the land. Although small tern flocks probably moved westwards within 22 km of the coast, but outside their detectable radar range, the results suggest that the majority of terns return through the Gulf of Guinea by a different route from that taken in autumn.

The difference between spring and autumn movements correlates well with the seasonal variation of the terns' food sources. In autumn, upwellings result in an abundant fish supply (sardines) in the surface waters close to land, whereas in spring, fish is abundant only well off shore such as at fronts (convergences) and upwellings (divergences) both of which have been located as far as 600 km from the coast.
FILTER‐FEEDING DUCKS OF THE KAFUE FLATS, ZAMBIA, 1971–1973
Authors: Douthwaite R. J.
Published: April 2008

The occurrence, chronology of breeding and wing‐moult, and feeding habits of seven commonly occurring species of filter‐feeding ducks on the Kafue Flats in Zambia are described, based on 20 aerial surveys over the central section of floodplain and intensive observations on the ground at Lochinvar National Park, between October 1970 and January 1974.

At high flood levels ducks were almost restricted to areas heavily utilized by lechwe; this association persisted until the floodplain became dry, but during the dry season ducks were also found on vegetated lagoons. Five species—Dendrocygna bicolor, Dendrocygna viduata, Thalassornis leuconotus, Netta erythropthalma and Anas erythrorhyncha—were most abundant between June and September; a sixth—Anas punctata—was most abundant between December and March, while the seventh—Anas undulata—was probably resident. At times the numbers of D. bicolor, D. viduata and A. erythrorhyncha probably exceeded 25 000; those of N. erythropthalma reached 6500, but the numbers of T. leuconotus, A. punctata and A. undulata were much lower and at Lochinvar did not exceed 500.

Small numbers of D. bicolor, N. erythropthalma, A. punctata and A. undulata nested on the floodplain in the vicinity of Lochinvar between March and July. All seven species completed their wing‐moult between April and October in the area; large numbers, particularly of A. erythrorhyncha and D. bicolor, were involved.

At Lochinvar, A. punctata fed mainly on aquatic invertebrates; the remaining species fed largely on shed fruits and seeds. The most important food plants were a terrestrial herb, Ambrosia maritima (January–April), two aquatic herbs, Nymphaea capensis and Nymphoides indica (May–August), and two aquatic grasses, Echinochloa stagnina and Vossia cuspidata (September–December). The herbs grew where grassland had been suppressed by lechwe; fruits of the aquatic grasses were found where lechwe had removed the overlying mat of stems. Despite similarities in diet the ducks differed from each other in feeding behaviour and/or preferred habitat.

Five other species of filter‐feeding ducks, Anas capensis, Anas smithii, Anas clypeata, Anas acuta and Anas querquedula, have been recorded from the Flats, but all are rare.
ASPECTS OF THE BEHAVIOUR AND ECOLOGY OF MIXED‐SPECIES BIRD FLOCKS IN KASHMIR
Authors: Macdonald D. W. , Henderson D. G.
Published: April 2008

Mixed‐species flocks of birds were observed between the end of July and late August, principally at Daksum, Kashmir, 2250 m. The species composition and the numbers of individuals in flocks changed during this period; these changes are attributed to resident territory holders and migrant birds joining the flocks. Within the flock different species showed some differences in foraging stations, but nevertheless often appeared to be taking the same type of food. Participant species had different roles in the flock organization. Behaviours involving the entire mixed‐flock acting as a unit included path reversal after encounters with avian predators and a tendency to follow set routes. The mixed‐ species flock exerted an attractive influence on aggregations of species not normally participant.

Similarities between the flocks described in this study and those recorded by other workers are discussed. While different species may derive different benefits from joining these flocks, advantages that could benefit some or all participants include the receipt of information on good feeding areas in an unfamiliar locality, the avoidance of time wasted on feeding on substrates which have been very recently harvested, the beating effect to increase prey availability, and enhanced safety from predators, perhaps through differential alertness of different species and specialized anti‐predator behaviour.
MIGRATION OF THE NORTHWESTERN EUROPEAN POPULATION OF THE CUCKOO CUCULUS CANORUS, AS SHOWN BY RINGING
Authors: Seel D. C.
Published: April 2008

The migration of the Cuckoo Cuculus canorus is described from recoveries of ringed birds. Young birds begin to migrate in August and most go southwards by September—those in continental Europe move southeast, south or southwest, while those from the British Isles move southeast. In spring, migrants arrive in Europe in April/May, second‐(calendar) year birds doing so later than post‐second‐year birds. In autumn old birds depart in advance of first‐year birds; and the individual bird may move stepwise through Europe. Old birds showed a marked tendency to return to the same places inhabited in previous breeding seasons, and birds ringed as nestlings subsequently tended to return to the general vicinity of the natal site.
SOCIAL ORGANIZATION AND NEST‐BUILDING IN THE FOREST WEAVER BIRDS OF THE GENUS MALIMBUS (PLOCEINAE)
Authors: BROSSET A.
Published: April 2008

A comparative study was made of social organization during breeding among the genus Malimbus. In M. nitens, the male chooses the nest site, builds the nest alone, guards the nest during incubation, and feeds the young; the female incubates, broods alone and with the male feeds the young. In M. malimbicus, the male chooses the nest site, builds the nest with the female and guards the nest; the female builds the nest with the male, but incubates alone. In M. racheliae and M. cassini, the nest is built by one female and a multi‐male party of two or three. One male drives off the other males when the nest is completed. One male and one female incubate alternately. The female seems to be the leader of the building group, and works like a male. In M. coronatus, the nest is built by a mixed party of males and females (3–6 birds), all working together without any overt leadership. Only one male and one female however, incubate, brood and feed the young.

In their morphology and behaviour, Malimbus spp. are close to the weaver birds of the genus Ploceus. M. nitens seems the least evolved species while M. cassini and M. coronatus are behaviourally the most evolved. In the last species, which has a very elaborate nest, the pair of breeding birds is helped by one to four other birds. These helpers are birds in full adult plumage, and are probably capable of breeding and may do so at another period in the long breeding season of at least six months.
THE EFFECTS OF DIURNAL AND TIDAL PERIODICITIES IN THE NUMBERS AND ACTIVITIES OF HERRING GULLS LARUS ARGENTATUS IN A COLONY
Authors: GALUSHA JOSEPH G. , AMLANER CHARLES J.
Published: April 2008

The average numbers of Herring Gulls Larus argentatus present in a breeding colony on Walney Island, Cumbria, were found to vary with the tidal cycle but to remain effectively constant with time of day through the breeding season.

An activity survey, based on 50 Herring Gulls observed at half‐hourly intervals during March and April 1973, showed that sleep and rest varied inversely with each other with sleep increasing to 50 per cent at midday. After a peak in the proportion of gulls asleep four hours before low tide, sleeping progressively decreased until low tide; seemingly a result of resident gulls waking and remaining more alert as others left the colony in search of food. Preening was constant throughout the day and tide cycle. Other behaviours (mostly courtship and agonistic behaviour associated with territory defence) increased slightly during low tide and were more common early and late in the day.

Night observations of the gulls' activities showed that there was a peak of sleeping between midnight and 02.00 hours. It is suggested that Herring Gulls have a bimodal diel sleep pattern.
SELECTION OF COLONY SITES AND NEST SITES BY COMMON TERNS STERNA HIRUNDO IN OCEAN COUNTY, NEW JERSEY
Authors: BURGER JOANNA , LESSER FRED
Published: April 2008

Common Terns nested on 34 of 259 saltmarsh islands along 46 miles of Ocean County coastline, New Jersey. They nested on low islands of Spartina with less than 12%, windrow ranging in size from 0.6 to 108 acres. All islands selected by terns faced at least two miles of open water from at least one direction. Selection of islands seemed a response to vegetation, size, distance to the nearest island, distance to the nearest shore and exposure to open water. Of the 225 islands without nesting terns, only three fulfilled appropriate criteria.

Eighty per cent of nests were situated on windrow. Terns laid larger clutches on windrow compated to those nesting in Spartina. Nearest neighbour distance on islands with low predation varied from 85 to 485 cm and was a function of space, vegetation, and the size of the island. Terns nested closer together on windrow compared with Spartina. Considering all colonies, the mean nearest neighbour distance negatively correlated with the number of nests.

Skimmers, Oystercatchers, Laughing Gulls, and Herring Gulls nested in some of the tern colonies. All tern colonies on islands also occupied by nesting Herring Gulls suffered over 10% egg‐loss by predation. Proportionally more nests were preyed upon in windrow than in Spartina. Clutch sizes in nests in windrow on islands with predation were significantly lower than those in windrow on islands without predation, even though clutch sizes in Spartina were similar on islands with and without predation.

Flooding by exceptional high tides destroyed significantly more nests in Spartina than in windrow. The nests that survived in Spartina were built deeper, and their rim heights were higher than nests destroyed by tides.

Choice of colony and nest sites is discussed in terms of the balance of two selection pressures: predation and tidal flooding. Tern nests on windrow are more exposed to predators, but safer from flooding, whereas those nests in Spartina are more susceptible to flooding and less vulnerable to predators. The recent invasion of Herring Gulls into Ocean County has significantly increased the rate of nest predation among affected colonies of Common Terns. It is possible that in future years the terns' behaviour may be modified in response to this new selective pressure.
SEED DENSITY, COVER, PREDATION AND THE DISTRIBUTION OF BIRDS IN A BEECH WOOD IN SOUTHERN SWEDEN
Authors: NILSSON SVEN G.
Published: April 2008

The distribution of six species of birds within a beech wood was analysed in two winters when beech seeds were abundant. All species were concentrated in patches where seed density was high in one winter, but only two showed a similar distribution in the second winter. The distribution of the other four species, three tits Parus spp. and the Nuthatch Sitta europaea, was positively correlated with low cover. Cover was inversely correlated with seed density. Bird predators were recorded many times during the second winter but not at all during the first winter. It is suggested that predator avoidance was more important than food density for some species in the second winter.

The relationships between bird density and both food and cover were sigmoid in shape.

The proportion of the seed crop consumed by the birds was estimated at about 4.5%, which was probably more than the amount consumed by mammals. The Woodpigeon Columba palumbus (which took 44% of the total seeds consumed by birds) and the Brambling Fringilla montifringilla (33%) were the most important seed consumers among the birds.
SHOREBIRDS OF COASTAL BUENOS AIRES PROVINCE, ARGENTINA
Authors: MYERS J. P. , MYERS L. P.
Published: April 2008

The Pampas shorebird community is comprised of species from diverse taxonomic and faunal origin. Four major groups can be recognized: North American migrants residing in coastal Buenos Aires Province during their non‐breeding season, Patagonian species wintering locally but breeding further south, Pampean species breeding locally, and Brazil–Paraguayan species present during their breeding season. Because of differences among these groups in the timing and migration patterns, community composition shows marked seasonal variation. Both nesting and non‐breeding birds use a diversity of habitat types ranging from littoral sandy beaches to upland grasslands. Throughout the year, however, and in all habitat types, non‐breeders predominate in species number and abundance. Intra‐ and inter‐specific patterns of aggression suggest both that resources are limiting, and that non‐breeding migrants may play an important role in determining breeding community composition.
BREEDING BIOLOGY OF THE DARTFORD WARBLER SYLVIA UNDATA IN ENGLAND
Authors: BIBBY COLIN J.
Published: April 2008

The breeding biology of Dartford Warblers was studied during 1975–1976 in 1010 ha of heathland on the Purbeck peninsula, Dorset; comparisons are drawn from other areas of the species' range. Clutches were of 3,4 or 5 eggs, with the mean clutch size increasing progressively from early May to mid‐June, declining thereafter. Incubation and brooding of the young were shared unequally between the sexes, with the female taking the greater part. In the number of feeding visits to nestlings there was no difference between the sexes until the last four days of nest‐life, when the male greatly increased his share. Nesting was comparatively successful (about 80% of nests producing some young), though the incidence of single infertile eggs was high. There were large variations between years and sites in the timing of the starting of laying. Late‐laying pairs reared only one brood, while early starters could rear two. Timing of starting, influencing the number of broods reared, appeared to be the most important factor causing variation in breeding productivity. No vegetational characteristics were entirely adequate to explain variation in starting dates. Past data, however, showed earlier starting in Sussex and Jersey where gorse was a more abundant component of the vegetation of Dartford Warbler habitat than in Dorset. It is suggested that the abundance of gorse is directly related to the quality of the habitat for Dartford Warblers, and hence to breeding productivity.
FACTORS AFFECTING THE EGG SIZE OF RED‐BILLED GULLS LARUS NOVAEHOLLANDIAE SCOPULINUS
Authors: MILLS J. A.
Published: April 2008

The factors influencing the egg size of the Red‐billed Gull Larus novaehollandiae scopulinus were studied at Kaikoura, New Zealand, between 1964 and 1972. In two‐ and three‐egg clutches there was a trend for the eggs to become smaller in the sequence of laying. Length, breadth and volume of eggs of one‐, two‐ and three‐egg clutches declined significantly as the season progressed. The size of eggs from single‐egg clutches tended to be smaller than eggs from two‐egg clutches laid at the same time.

There were correlations between the proportions of one‐egg and of three‐egg clutches being laid at a given period and the mean egg volume of two‐egg clutches. When the mean egg volume of two‐egg clutches increased there was a corresponding increase in the proportion of two‐ and three‐egg clutches laid. When the mean egg volume of two‐egg clutches decreased there was an increase in the proportion of single‐egg clutches laid.

The egg size of the Red‐billed Gull showed no direct correlation with the abundance or availability of food; the largest eggs were produced early in the season when food was in short supply. In spite of an increase in the food supply in the middle of the breeding season, birds laying at this time produced smaller eggs than birds which laid earlier in the season. However, early breeders which relayed at the peak in food abundance on average produced a larger replacement clutch than originals laid early in the season. It is suggested that the birds nesting early in the season are able to produce the largest eggs because they are the most efficient foragers for food, and those which nest later in the season produce smaller eggs, even at peak food abundance, because of their inefficiency or inexperience. Early breeders laying replacement clutches tended to lay larger eggs and larger clutches than birds which are producing their first clutches at the same time.

Two‐year‐old females laid eggs which were significantly shorter than older aged birds while the breadth and volume of the egg increased with the age of the female up to the fifth year. There was a trend for females to lay larger eggs when mated with older rather than younger males. No statistical differences in egg size were detected between females changing or retaining the partner of the previous season. Female body weight and egg volume were positively correlated in females weighing less than 275 g but not for heavier females.

It is suggested that the seasonal decline in egg size and clutch size results from a decrease in the availability of food and the ability of the individual to exploit the resource.
DEVELOPMENT OF THE MAGNUM REGION OF THE OVIDUCT IN RELATION TO THE REPRODUCTIVE CYCLE OF THE BARBARY DOVE STREPTOPELIA ROSEOGRISEA VAR.
Authors: HUTCHISON R. E.
Published: April 2008

The magnum region of oviducts of female Barbary Doves was examined at different phases of development before egg laying, and during incubation and brooding of the young. The tubular glands in the mucosal folds of the magnum region increased in size with increase in precursor albumen granule content during the pre‐egg‐laying phase, and decreased during incubation and brooding. Enlargement of tubular glands was correlated with an increase in plasma progesterone level. The temporal relationships between ovarian development, ovarian hormones, oviduct development and nesting behaviour are discussed.
THE BIRD COMMUNITY OF TASMANIAN TEMPERATE RAINFOREST
Authors: Thomas D. G.
Published: April 2008

The avifauna of Tasmanian temperate rainforest consists of 21 species, more than hitherto reported. Eleven species are very common, six are common and a further four species that have large home ranges are uncommon. Other species occur occasionally or accidentally.

The structure of the Tasmanian rainforest community was determined from measured overlaps in horizontal habitat selection, vegetation layer utilization and foraging site distribution. This demonstrates the existence of guilds, the members of which react more with each other than they do with members of other guilds. Niche differentiation is shown in each guild in the breeding season. However, adaptations enabling survival during the non‐breeding season may be important in the seasonal Tasmanian environment.
WHY FORAGING BIRDS IN TREES SHOULD CLIMB AND HOP UPWARDS RATHER THAN DOWNWARDS
Authors: Norberg R. Åke
Published: April 2008

This paper describes the energy cost of locomotion in birds foraging over vertical zones in trees. In particular, the energetically cheapest pattern for a bird flying among trees and moving within them is explored. For birds moving vertically by climbing and hopping (but not by flying) it should take less energy to climb and hop upwards in a tree and fly downwards to the next one, than to do the reverse. This is because part of the potential energy gained in climbing upwards may be used for subsequent horizontal progression to the next tree. For movements the other way, the potential energy is largely wasted during downward hopping and climbing within a tree.

It is predicted that birds moving within trees by climbing and hopping (but not by flying) leave at a higher level than they arrive (whether the vertical movements within trees are along the trunk or among branches).

These energetic considerations probably expose one selection pressure behind the morphology of the woodpecker—treecreeper type, which shows obvious adaptation for climbing upwards rather than downwards.
CLUTCH SIZE, EGG SIZE, HATCH WEIGHT AND LAYING DATE IN RELATION TO EARLY MORTALITY IN RED GROUSE LAGOPUS LAGOPUS SCOTICUS CHICKS
Authors: Moss R. , Watson A. , Rothery P. , Glennie W. W.
Published: April 2008

Clutches of Red Grouse eggs were collected from the wild and subsequent hatching and rearing done in standard conditions in captivity. Variations in chick survival from one clutch to another in the same year were related to differences in hatch weight. Hatch weight was determined only partly by egg size. Weight loss between laying and hatching was related to survival independently of egg size. Variation in this weight loss obscured any simple relationship between egg size and survival, except in eggs laid by captive hens.

Intrinsic differences amongst hens caused some variations in laying date, egg size, hatch weight and chick survival. Variations in egg size and hatch weight accounted for less than half the variation in survival; other unmeasured intrinsic factors were also important.

Big clutches hatched earlier than small ones. The commonest clutches were of seven and eight eggs, with six and nine frequent. Very big clutches of ten or more eggs were infrequent and chicks from them sometimes survived worse than from smaller clutches.

As in other species, the commonest clutch sizes were not the most productive. There was no simple relationship between egg size and clutch size.
SIZE, FORM AND HABIT OF THE EXTINCT MALTESE SWAN CYGNUS FALCONERI
Authors: NORTHCOTE E. MARJORIE
Published: April 2008

The giant extinct Maltese Swan is shown in this work to have been a land‐feeding bird, well adapted for walking but with little or no ability to fly. Fossils of the swan prepared during this study comprise the most representative remains in existence; the greater part of the foot skeleton and the frontal part of the cranium are described for the first time. By comparison of the bones with those of living swans I estimate that it probably resembled a scaled‐up Whooper Swan weighing about 16 kg and with a wing span of about 3 m.
NESTING OF THE VILLAGE WEAVER PLOCEUS CUCULLATUS
Authors: CAMARA‐SMEETS M. DA
Published: April 2008

From August to October 1975, 31 nesting colonies of Village Weavers were identified within an area of 3000 km2, south of Lake Chad in Africa. The number of nests and the productivity of each colony were estimated by means of several samplings made during the course of the nesting season.

Differences between bush colonies and village colonies are not relevant. The average length of the nesting season is 70 days. In each colony the number of nests increases during the first month and then decreases. The average number of fledging attempts is four per colony, with a period of about ten days from one to another. On a regional scale, breeding periods and fledging attempts are well synchronized. Each nest carries an average of 2.4 eggs and 1.9 young, the difference occurring only at hatching. Due to regional synchronism, the period of most intensive reproductive activity, at which the number of nests reaches its maximum, can be determined.
COOPERATIVE BREEDING IN A POPULATION OF WHITEBROWED SPARROW WEAVERS PLOCEPASSER MAHALI
Authors: LEWIS DALE M.
Published: April 2008

This paper reports on a three year study describing cooperative breeding and demography of a sampled population of approximately 108 colour‐marked White‐browed Sparrow Weavers in Zambia. Twenty‐seven communal groups with two to 11 individuals in a group made up this population and occupied a l km2 area of mopane woodland. Each group had only a single reproductive pair and the pair‐bond appeared strong. Non‐reproductives were generally siblings or half‐siblings and they contributed a major share of nestling feeding, nest building, intruder chasing and guarding. Groups cooperatively built nests in certain preferred trees and they maintained their nests year round. Feeding range encircled the nesting site and was used almost exclusively by the communal group.

Overall population density was relatively stable, and between‐year variation in group size was significantly greater than within‐year variation. Variation in annual reproductive success among groups was high and correlated positively with size. Mortality rates for nestlings, six‐month‐olds and juveniles were not correlated significantly with group size. Frequency of disappearance for reproductives of both sexes was correlated negatively with group size.
Habitat partitioning and antagonistic behaviour amongst the birds of a West African scrub and plantation plot
Authors: Edington John M. , Edington M. Ann
Published: April 2008

A study was made of feeding patterns and antagonistic behaviour amongst 11 common bird species frequenting an abandoned rubber plantation and scrub plot in southern Nigeria.

The examination of feeding patterns involved a comparison of foraging habits and an analysis of the use made by each species of the major vertical and horizontal subdivisions of the habitat. Two species of muscicapid flycatchers showed a striking similarity, both in foraging habits and their use of the major habitat zones. In general, however, species with otherwise similar foraging habits were found to feed in habitat zones which were spatially separated.

A number of these latter species showed antagonistic reactions to one another. However, unlike most reported instances of such behaviour in birds, neither species in the pairs we observed played a consistently dominant role. Dominance was usually shown by whichever individual made most use, for feeding purposes, of the encounter zone.

Under these circumstances it seems possible that interspecific antagonism allows species to adjust to local variations in habitat structure and to capitalise on the temporary absence of potential competitors. In which case it is more appropriate to regard this type of behaviour as an important component in the process of habitat partitioning, rather than to dismiss it as an activity which will ultimately be rendered redundant in the course of evolution.
Intraordinal relationships of the Pelecaniformes and Cuculiformes: electrophoresis of feather keratins
Authors: Brush Alan H. , Witt Hans‐H.
Published: April 2008

Electrophoresis of soluble feather keratins was performed in Gradipore gels under two pH conditions. The taxa of two diverse orders, the Pelecaniformes and Cuculiformes, were compared. Dendograms based on identity indices and genetic distances were constructed by the Fitch‐Margoliash and unweighed pair‐group algorithms (UPGMA). Differences within taxa were influenced by both pH conditions and the algorithm used for analysis.

Values of identity indices at each pH were compared within and between taxa. Dendograms for the Pelecaniform consistently group species within genera and placed families within the traditional arrangements. One notable exception was Nannopterum. The Cuculiformes, with many monotypic genera, were more resistant to constant clustering.

The problems of relating genetic distance to phylogenies are discussed. The relationship of systematic, ecological and molecular diversity is still unresolved. Genetic distance of feather keratins consistently correlated with other estimates of divergence times. The values indicate the systematic equivalence of taxa within orders.
Heat stress in tropical birds: behavioural thermoregulation during flight
Authors: Bryant David M.
Published: April 2008

Pacific Swallows and Blue‐throated Bee‐eaters in Malaysia commonly exposed their legs when flying. The habit was most frequent around midday and was interpreted as a mechanism to dissipate heat and thereby reduce stress. The main cause of heat stress was thought to be solar radiation combined with high endogenous heat production during flight. Stress was probably increased by high ambient temperature and humidity. The occurrence of leg exposure during flight in a total of 17 species showed the habit was widespread among open habitat species in Malaysia.
Ecological character displacement and character release in grebes Podicipedidae
Authors: Fjeldså Jon
Published: April 2008

The paper is based on measurements of 2925 grebes and extensive field studies on ecological segregation and resource exploitation of the grebes of northern Europe, Colombia, Peru, Patagonia and Australia.

In all examined cases where two closely related grebe species overlap locally, one or both showed indications of divergent bill morphology. In two cases there are indications of evolutionary changes during the present century. In the case of the grebes of the Junin and Titicaca basins and for one European species, it was found that the morphological change reduced the interspecific food overlap.

There is a statistical tendency for evolution of a quite specific bill (21–26 mm long, 88‐9‐8 mm high, 7‐6‐8‐5 mm wide) in isolated areas with only one grebe species. A close examination of one of these populations suggests that this bill type is an ‘all‐purpose’ one which permits opportunistic fish‐eating without loss of the ability to feed efficiently on tiny arthropods. In the case of two or more sympatric grebes, there appears, on a worldwide scale, to be a compulsory radiation away from the ‘all‐purpose’ bill type.

The data suggest the existence of co‐evolution in grebe faunas. Birds living under poor feeding conditions have to exploit all potential foods available, while specialization on optimal foods takes place where it is easy to find. Small individual differences in the trophic organs thus influence the diet only in relatively prolific habitats. Character displacement is therefore most likely to take place in stable environments inhabited by K‐strategists, whose biotic adaptations keep their populations on levels where individual birds generally have more food than the bare necessity.
Sex ratio, survival and territorial behaviour of polygynous Hen Harriers Circus c. cyaneus in Orkney
Authors: Picozzi N.
Published: April 2008

Polygyny is widespread among Orkney's Hen Harriers Circus cyaneus. From 1975–81, it was associated with a sex ratio estimated from resightings of colour‐marked birds up to six years of age to be 29 females:ten males. The sex ratio of fledglings changed significantly from a greater proportion of females in the 1950s and early 1960s to a greater proportion of males subsequently. The mean estimated ‘survival’ rates (birds colour‐marked in Orkney which were seen there in later years) of males and of females 0–2 years old were 14 and 29%. The mean estimated annual survival rates of males and females from 2–6 years old were 72 and 90%. It is suggested that the uneven sex ratio resulted in more frequent intra‐sexual encounters and displays by females. The results of temporary removals of two females (immediately replaced) and of two males (not replaced) in spring indicates that there was a shortage of males in the population.
An example of character release in host selection and egg colour of cuckoos Cuculus spp. in Japan
Authors: Higuchi H. , Sato S.
Published: April 2008

We have studied in northern Japan the hitherto unidentified eggs of a species of cuckoo in the nests of the Bush Warbler Cettia diphone. The cuckoo in question appeared to be the Himalayan Cuckoo Cuculus saturatus which parasitizes mainly the Willow Warbler Phylloscopus occipitalis in southern Japan. The egg colour in this northern Cuckoo was chocolate‐brown or orange‐brown, similar to that of the Bush Warbler but unlike that of the southern Himalayan Cuckoo. Egg size was significantly larger than that of the southern Himalayan Cuckoo and instead similar to that of the Little Cuckoo C. poliocephalus which uses the same host species in southern Japan, to which the Little Cuckoo is confined. The shift in host species and egg colour in the northern Himalayan Cuckoo seems to be a case of character release in the absence of the Little Cuckoo.
Survival and age related changes in the foraging behaviour and time budget of Tufted Ducklings Aythya fuligula
Authors: Hill D. A. , Ellis N.
Published: April 2008

The time budgets of Tufted ducklings Aythya fuligula changed radically as they matured, particularly during the first 12 days of life—the most critical time for survival. The amount of time spent skimming for surface chironomids declined during the period from hatching to 21 days. Time allocated to diving increased during this period. Ducklings between the ages 12–37 days visited land in order to preen and sleep during the day. Time spent preening on land increased up to 21 days of age and declined thereafter. Diving rate was highest in ducklings of the 20–30 day age category and declined in those older than 30 days. The amount of time spent under water on each dive, equated with diving success, increased with age.
Long‐term defence of fruit by Mistle Thrushes Turdus viscivorus
Authors: Snow Barbara K. , Snow D. W.
Published: April 2008

In an area of south‐central England Mistle Thrushes Turdus viscivorus regularly defend fruit‐hearing plants (four kinds of tree, ivy and mistletoe) against intruders from autumn to early spring. Holly Ilex aquifolium is by far the most important of the plants defended. To be suitable for defence, a tree must be free‐standing and of moderate size. Observations were carried out over three winters, one mild, one very severe and one intermediate. During the mild winter hollies were successfully defended until the Mistle Thrushes gave up active defence with the onset of breeding activities. During the very severe winter nearly all defended hollies were overwhelmed by invading flocks of other thrush species during the very cold spells. Mistle Thrushes in possession of a fruit supply conserve it by feeding on undefended fruit near‐by if it is available, and to a large extent on the ground when conditions are suitable. Defended fruit trees are generally avoided by other species living in the vicinity. Hence depletion of fruit from defended trees is much slower than from undefended trees, and consequently the fruit may last for several months and provide a food supply in dry weather in spring and early summer for Mistle Thrushes and other species.

Fieldfares and Blackbirds show similar, but less well developed, fruit‐guarding behaviour. Fruit‐defence is clearly related to the bird's size, but other physical and behavioural adaptations may be involved. The most important characteristic of holly fruit making it suitable for defence, apart from the dimensions and spatial relationship of the tree, is its ability to last for many months without significant deterioration.
The breeding biology of the Pacific Swallow Hirundo tahitica in Malaysia
Authors: HAILS C. J.
Published: April 2008

The breeding biology of the Pacific Swallow was studied in Malaysia. Time‐budgets and preliminary energy‐budgets were calculated for different stages of the breeding cycle. Breeding was seasonal, the first eggs were laid in the first week of March from 1978 to 1982. The nest was a mud cup built under an overhang, often on man‐made structures over water. The mean clutch size was 2.98 eggs. So more than two successful clutches were ever raised, although up to four sets of eggs can be laid if clutches are lost. The incubation period was 16.2 days and the nestling period 19–21 days. Nestling weights showed the typical hirundine recession before fledging. The mean brood size was 2.32 and there was no evidence of undernourishment in larger broods. Nesting success was lower than for temperate hirundines but high for a tropical passerine. Incubation duties were carried out by the female alone but both parents fed the brood. The male never delivered more than 44% of the total feeds. Daily energy expenditure varied from 3.44–4.9×BMR depending upon the stage of the breeding cycle.
Seed preference and energy intake of Goldfinches Carduelis carduelis in the breeding season
Authors: GLÜCK ERICH E.
Published: April 2008

The food of a population of Europeans Goldfinches breeding in Orchards was studied. More than 5% of the total foodstuff consumed was met by the seeds of seven food plants. Water, lipid, carbohydrate and protein content was determined from 20 different plants which Goldfinches used during the breeding season in order to calculate energy content. The energy of fresh seeds varied from 1.88 kJ/g in Tussilago farfara to 12.14 kJ/g in Dactylis glomerata. The dependence of the rate of energy intake (profitability) on the pecking rate and the size (weight) of the seeds was calculated. The profitability of various seeds is in agreement with the relative number of birds using them. Calculation of the feeding time that a Goldfinch needs during daylight hours, if it feeds only on a particular plant, indicates that there are several foods that cannot fill the energy demands of the bird during the breeding season. These are eaten only if others with a high energy content are not available. Thus food selection in Goldfinches depends, apart from availability, on seed profitability. The oxygen consumption of a male Goldfinch was significantly higher when the animal was feeding on seed heads of Tussilago farfara and Taraxacum officinale than when it fed on loose dry seeds, and so, different feeding techniques have to be taken into account in calculating net energy gain.
Morphological and genetic variability of Snow Petrels Pagodroma nivea
Authors: JOUVENTIN PIERRE , VIOT CHRISTOPHER‐ROBIN
Published: April 2008

Snow Petrels vary greatly in size, the largest birds being over twice as heavy as the smallest. Two morphological types have been distinguished, but the Adelieland population alone shows continuous variation spanning the complete range of the species. There is no evidence of size‐related assortative mating. Size variation cannot be attributed to nest site location nor to individual age, nor is the large sexual dimorphism sufficient to account for the situation. The great individual variation in size is accompanied by an important genetic variability as revealed by a starch gel electrophoretic study.

Comparisons of wing length data from many localities around the Antarctic Continent suggest a cline, with a peak at the Balleny Islands. Taking into account the extent of size variation at breeding places only, it appears that morphological variability is low at Balleny Islands, where only large form birds are known, and at Antarctic localities inhabited exclusively by small form birds. In contrast, several localities on the continent in the vicinity of Balleny Islands, and especially Adelieland, exhibit a high degree of variability.

We propose that during the quaternary glaciations, the Antarctic continent provided no refugia for this species, but, when glaciation ended, Snow Petrels re‐established colonies, coming from two refugia, a low latitude one inhabited by small birds Pagodroma nivea nivea, and one in higher latitudes characterized by large birds P. n. major. Reproductive isolation broke down, and a hybridization zone was created. The high proportion of polymorphic loci exhibited by the Adelieland population is then attributable to the mixing of two previously isolated genetic pools.