bluuebunny/crossref_metadata_2025 huggingface dataset:
BREEDING DENSITY IN THE PEREGRINEFALCO PEREGRINUSAND RAVENCORVUS CORAX
Authors: Ratcliffe D. A.
Published: April 2008

The relative stability of breeding density in the Peregrine and Raven in certain inland districts is examined in relation to population limiting factors. Problems of cenus‐making are considered, particularly the use of alternative nesting places. Breeding populations of the Raven have not fallen below 15% of the maxima since 1945. While the Peregrine now shows signs of local decline, it had numeral stability equal to the Raven during the preceding period, and this is the state under consideration.

Of possible controlling factors, food supply is unlikely to be directly limiting. For breeding to occur, cliffs suitable in altitude, vertical height, cover and presence of ledges are necessary. Alternative cliffs and ledges are used if available but are not essential to ensure regular occupation of a territory. Availability of suitable cliffs controls nesting density at the lower levels, but does not impose an upper limit.

The Golden Eagle is a dominant competitor for nesting cliffs and perhaps for food, and when nesting space is limited Peregrines and Ravens may compete with each other for cliffs. Deliberate persecution can deplete adult populations temporarily and reduce breeding success, especially in the Peregrine, but does not limit breeding density over a period, except in unsuitable terrain. For both species, breeding success and/or migration are sufficient to maintain numbers in the study regions. When breeding success is high, no increase in nesting populations follows. The Raven has non‐breeding surplus populations during the breeding season but this is less certain for the Peregrine.

Although direct evidence for its existence as defence of an area is scanty, territorialism is regarded as the factor controlling maximum nesting density by producing a “proximity tolerance limit” between adjacent nesting pairs. It is believed that such territorialism is not itself an ultimate limiting factor but has evolved in relation to food supply so that the numbers of predators are permanently balanced against this factor.
RADAR OBSERVATIONS OF BIRD MIGRATION IN CYPRUS
Authors: Adams D. W. H.
Published: April 2008

Observations by radar were made of bird migration in Cyprus in October and November 1958 and March to May 1959.

Migration was found to occur almost daily, usually beginning three‐quarters of an hour after sunset.

The standard direction of migration in October was S. to S.S.E., but in November there were movements both S. to S.S.E. and S.S.W. to S.W.

Most spring migrants flew tracks between N.N.E. and N.E., but about 10% flew N.W., including the largest single passage recorded.

Some bird‐tracks were seen avoiding high ground and coasting at high altitudes by day, and once by night in bright moonlight.

The significance of the results is discussed.
MIGRATION ACROSS THE SOUTHERN NORTH SEA STUDIED BY RADAR PART 5. MOVEMENTS IN AUGUST, WINTER AND SPRING, AND CONCLUSION
Authors: Lack David
Published: April 2008

Arrivals of gulls S.W. seem almost confined to late July.

In August, the main movements are W. by day and night of Lapwings and S.S.E. by night of warblers. Sand Martins migrated at dawn directly from a large roost at 34 m.p.h.

In midwinter, migration occurred in at least one direction almost every morning and night. “Hard‐weather movements” west or south are initiated primarily by easterly or northerly winds respectively, and not by cold. The corresponding return movements, which sometimes follow immediately, arc initiated primarily by westerly or southerly winds respectively, but warmth has an influence in February. In midwinter, various species are evidently ready to travel in either the autumn or the spring direction, and wind‐direction is the paramount factor determining which occurs.

The big eastward departures in March and April occur mainly with westerly winds and in warm weather, both factors being important, but proportionately more departures occur against strong head or cross‐winds than in autumn. The general weather situation has no direct influence.

Starlings migrated directly from their roosts on a few mornings each spring, normally at sunrise but on one occasion some did so much earlier.

In late April and May the chief movements are N.N.W. arrivals and onward passages of British summer visitors, N.E. departures of shore‐birds, and N.N.E. departures of small passerines, presumably en route between Iberia and Norway. These movements occur mainly with southerly winds, but sometimes against the wind.

“Reversed movements” W. or S.S.E. are much more frequent in spring than has previously been supposed. They occur exclusively with easterly or northerly winds respectively (like the midwinter movements).

The frequency of each migratory movement throughout the year is summarized in Table 6.

The main findings of the 5‐year study are reviewed under four heads in the Conclusion.
THE PLUMAGE OF THE RED AVADAVAT AMANDAVA AMANDAVA AND ITS EFFECT UPON CONTACT BEHAVIOUR
Authors: Sparks. John H.
Published: April 2008

Goodwin (1962) has commented upon the capricious, variable nature of the two plumages of the cock Red Avadavat Amandava amandava. At any time of the year cocks in the ‘red’ nuptial plumage can be found, but birds moulting into the ‘hen’ type post‐nuptial (eclipse) plumage occur most frequently between December and February. In captivity, the annual rhythm is upset and is inconsistent from year to year. In my experimental colony, all the cocks moulted into their post‐nuptial plumage during March 1962 and donned their nuptial plumage in the following May, only to effect a complete change again by early in October. A year previous to this, in October 1961, they were still in their full ‘red’, nuptial plumage.
ARRIVAL DATES OF THE GARDEN WARBLER SYLVIA BORIN IN CENTRAL NIGERIA
Authors: Smith V. W.
Published: April 2008

These observations were made at Vom (9° 50′ N., 8° 50′ E.), which lies on the central plateau of Nigeria at an altitude of about 4,000 feet, in the Guinea Savannah vegetational zone. The small residential area of Vom is round the periphery of the cone of an extinct volcano. The gardens have varying numbers of tall trees (mainly eucalyptus species) and ornamental shrubs. In the immediate vicinity is open grassland, with small forestry reserves and deep water‐courses filled with varying amounts of dense bushy vegetation.
BRIEF NOTES ON THE BIRDS OF SAN AMBROSIO AND SAN FELIX ISLANDS, CHILE
Authors: Millie W. R.
Published: April 2008

San Ambrosio Island, together with San Felix 17 miles to the NNW, and the smaller González Islet form the San Felix Group situated on Lat. 26° 20'S and Long. 80° W. These islands, like all the others scattered off the Chilean coast, are outcrops of volcanic origin which emerge from depths as great as 10,000–14,000 feet below sea level. They lie 500 miles west of the port of Chañaral and about the same distance due north of Juan Fernandez (Robinson Crusoe) Island. As they lack fresh water and lie off the regular navigation routes, civilization has passed them by and, except for occasional visits by lobster fishermen, has left them uninhabited.
“DRUMMING” BY SWIFTS
Authors: Bednall D. K.
Published: April 2008

On 27 April 1958, while my wife and I were watching a party of 20–30 Mottled Swifts Apus aequatorialis over a dam ten miles west of Nairobi, Kenya, we repeatedly heard quite a loud “prrrpt‐prrrpt‐prrrpt”. We discovered that the swifts were making this noise by spreading and slightly depressing their tails and moving them sideways so that the outer feather was almost parallel with the wing. The ‘leading’ feather thus projected into the slipstream was quite clearly seen to vibrate at the same time as the noise was heard. We watched this performance for about half an hour and noted that the tails were invariably turned to the right; we were both using binoculars. We saw that several birds were performing in this manner but it did not appear to be in connection with any display towards any other particular member of the party. The sexes of the Mottled Swift are indistinguishable in the field. The ‘drumming’ took place in the early part of the dive towards the surface of the dam from which the birds were drinking on the wing; it did not appear to cause any deflection of the flight path.
INTER‐SPECIFIC RELATIONS BETWEEN SOME ANDEAN BIRDS
Authors: Moynihan M.
Published: April 2008

Four types of partly nectarivorous and partly insectivorous “honey creepers”, Diglossa lafresnayei lafresnayei, D. carbonaria aterrima, D. cyanea cyanea and Conirostrum cinereum fraseri are more or less common near Quito, Ecuador. They compete with one another to a very considerable extent, since their ranges are broadly overlapping, they occur in many of the same habitats, and they feed on many of the same flowers and types of insects in exactly the same places.

The relations between these birds are so distinctive and so obviously specialized that they may be considered to form a special social group or “complex”. Some of the reactions between individuals of different species in this complex are quite different from both their intra‐specific reactions and their reactions to other species (not belonging to the complex). This differential responsiveness is shown in three ways.

Individuals of different species of this complex never (or almost never) come close together, due to the fact that they deliberately refrain from approaching one another. They also keep apart from other individuals of their own species (except members of the same family group), but they do this by defending territories against such individuals, not merely by refraining from approaching them. They do not refrain from approaching individuals of any other species.

Individuals of different species of this complex never (or almost never) become openly aggressive toward one another; but they do show such hostility toward most other individuals of their own species and (usually to a lesser extent) individuals of all other species.

Individuals of different species of this complex usually refrain from singing simultaneously. They do not show the same degree of restraint when other individuals of their own species are singing, and they usually ignore the songs of other species.

All the distinctive features of the behaviour of the different species of this complex toward one another seem to be adaptations (or the results of adaptations) to permit them to live in the same areas and habitats, during the same general periods of time, and still remain segregated from one another at any given moment. There is reason to believe that this type of segregation may be more advantageous than inter‐specific fighting.

It seems likely that the members of this complex have been in contact with one another for a long time. Some of the morphological and behaviourial characters of lafresnayei, cyanea, and fraseri seem to be adaptations to the presence of aterrima. Theoretical considerations would suggest that there will be strong selection pressure against both further divergence and convergence of these forms as long as it continues to be advantageous for them to maintain the same interspecific relations with one another.
THE PELAGIC DISTRIBUTION OF THE SOOTY SHEARWATERPROCELLARIA GRISEA
Authors: Phillips J. H.
Published: April 2008

The breeding distribution of the Sooty Shearwater and the dates of its breeding season are briefly reviewed.

Records from the Southern Ocean are summarised. It is concluded that they are accounted for by non‐breeding birds feeding off the ice‐edge in the Australian sector of the Antarctic during the latter part of the breeding season.

The great majority of Sooty Shearwaters spend the southern winter in the Pacific Ocean. Birds from the New Zealand colonies are probably mostly found on the feeding grounds off Japan: some may make a “circular” migration around the Pacific. Birds from the Cape Horn colonies spend the southern winter in the rich areas off the western coast of North America.

Some Sooty Shearwaters spend the southern winter off the South African coasts. A number of non‐breeding birds remain there throughout the summer.

The Sooty Shearwaters “wintering” in the North Atlantic are probably numbered in tens of thousands only. The distribution of records is reviewed month by month and the records from Atlantic transects are summarised. The migrations in the North Atlantic are discussed in relation to prevailing meteorological and oceanographic conditions, and food supply. It is concluded that most Sooty Shearwaters in the North Atlantic make a “circular” migration, crossing the North Atlantic from west to east in June and July, and re‐crossing about September further south in the northeast trades.
THE BIOLOGY OF THE WIDEAWAKE OR SOOTY TERN STERNA FUSCATA ON ASCENSION ISLAND
Authors: Ashmole N. P.
Published: April 2008

Wideawakes Sterna fuscata were studied on Ascension between October 1957 and April 1959. As shown by Chapin, breeding in this species occurs every nine and a half months on Ascension, and two complete breeding periods were observed. Some of the birds are close to the island even in the non‐breeding period, and many settle on the breeding ground at night during the two months before breeding begins, although they suffer serious predation from cats at this time.

The Wideawakes breed in dense colonies, usually on rocky ground. The single egg is incubated by the parents alternately, in shifts which on Ascension last up to six days, probably indicating that food cannot be found quickly, close to the island. The fledging period is long, but the rate of development flexible: the young can survive long periods on very little food, but grow relatively fast when given more food. In spite of this adaptation many young died of starvation in the second breeding period observed, while those which survived took longer to fledge than the chicks raised in the previous breeding period. The chicks also suffered severe predation, from frigate birds when very young and from cats when older. Together, these factors resulted in strikingly low breeding success.

Individual Wideawakes on Ascension breed at intervals of 41–51 weeks, and between successive breeding periods undergo a complete moult: they finish one moult before returning to breed, but may start the next moult before their chicks are full‐grown. The length of the interval (9 months) between the start of laying in successive breeding periods appears to be determined by the time required for breeding activities, a complete moult, and an assembly and courtship period during which social stimulation is probably important.

In an appendix are listed the recorded times of breeding of Wideawakes in all parts of their range: previously undiscerned six‐monthly or non‐seasonal breeding is documented for several localities.
THE REGULATION OF NUMBERS OF TROPICAL OCEANIC BIRDS
Authors: Ashmole N. P.
Published: April 2008

The ways in which the numbers of tropical sea‐birds might be limited are considered; it is argued that food is the only factor likely to be generally effective in limiting numbers, but it seems improbable that food shortage could exert a density‐dependent control of the mortality of the birds outside the breeding season.

Wynne‐Edwards' hypothesis that colonies of sea‐birds are able to keep their own numbers below the level at which food shortage would become acute, primarily by exerting control on the output of young, is rejected as unproven and improbable.

It is suggested that colonies of tropical oceanic birds deplete the food in the waters round them, and that as the populations increase competition for food becomes more intense, and relatively fewer adults succeed in raising chicks. This would provide a density‐dependent control of the output of young and could regulate the numbers of the birds.

The peculiarities of long‐lived sea‐birds (e.g. clutches of one, long fledging periods, deferred maturity) which Wynne‐Edwards suggests are adaptations evolved in order to lower the reproductive rate until it balances the mortality, apparently could not be evolved as such; they are more probably adaptations enabling the birds sometimes to raise single chicks in spite of competition for food that makes it impossible to raise more than one. It is considered that variation in the age of first breeding provides an important supplement to variation in reproductive success in regulating the numbers of long‐lived tropical sea‐birds.

The possible applications of this hypothesis to sea‐birds breeding in higher latitudes are briefly considered, as are its implications in relation to conservation and exploitation of populations of sea‐birds.
THE LAYING DATES OF SOME ST. HELENAN SEA‐BIRDS, 1958‐59
Authors: Stonehouse Bernard
Published: April 2008

Laying dates of six species of sea‐birds on St. Helena were determined in the spring and summer of 1958–59 by members of the B.O.U. Centenary Expedition on two visits from Ascension Island. Laying dates of the same species on Ascension Island are compared. Only two species showed close seasonal agreement between the two islands.
THE FEEDING HABITS OF THE WOODPIGEON COLUMBA PALUMBUS, STOCK DOVE C. OENAS AND TURTLE DOVE STREPTOPELIA TURTUR
Authors: Murton R. K. , Westwood N. J. , Isaacson A. J.
Published: April 2008

The feeding‐sites of Woodpigeon, Stock Dove and Turtle Dove were examined in a study area in Cambridgeshire by making repeated standardized observations over five years. The crop contents of 614 Woodpigeons and 166 Stock Doves shot throughout the period were analysed to determine the birds' diet. Seasonal variations are detailed. The crop contents of 41 Turtle Doves, and the nestlings of 14 Stock Doves and 5 Turtle Doves were also analysed.

During the winter, Woodpigeons fed primarily on clover leaves which they collected from leys and pastures, but also on weed leaves and, during periods of snow, those of various cultivated brassicae. Grain was taken from the spring cereal sowings, after which the birds reverted to clover feeding, supplementing this diet with tree leaf and flower buds. When cereals ripened these comprised the main food being collected from July to November, at first from standing crops and then from stubbles. Wheat was preferred to barley. In the autumn, beech nuts, acorns and other tree fruits were taken and when stocks of these and the cereals were exhausted the birds turned again to clover feeding. Weed seeds, especially pasture species, were collected especially in May and June but only in small amounts.

Stock Doves fed primarily on weed seeds throughout the year, obtaining these from fallow ground, ploughed fields and cereal stubbles. Cereal seed was taken when available, but featured less in its diet than that of the Woodpigeon. The most important weed seeds were Sinapsis and Brassica species, Stellaria media capsules and Polygonum and Chenapodium species. Leaves or tree buds and fruits were not an important food item.

Turtle Doves fed primarily on the seeds of Fumaria and grass species, but they also collected cereal grains and Stellaria media capsules. They collected their food from waste ground or from tall, standing hay or corn crops, where many weeds were growing. They did not appear to feed from trees or hedgerows.

The food of nestling Stock and Turtle Doves was similar to that collected by the adults for themselves.

The feeding habits of the other British columbids is briefly reviewed. It appears that the Turtle Dove, Stock Dove and Woodpigeon, and also the feral pigeon and Collared Dove occupy different ecological niches, the first three associated with arable farmland. The Woodpigeon, Stock Dove and Turtle Dove have all increased in numbers and range following the development of agriculture. It is likely that the Rock Dove competes for food with the Stock Dove and possibly at times with the Woodpigeon, which probably explains the declining status of the Rock Dove in Britain.

The distribution of the Turtle Dove in Britain is similar to the distribution of Fumitory, its major food plant.
HEAT LOSS IN WET DUCKLINGS AND CHICKS
Authors: Nye Pauline A.
Published: April 2008

Wet ducklings, like wet chicks, had lower body temperatures than dry birds. The temperature depressions of the chicks decreased as they grew older. The temperature depressions of the ducklings were mainly dependent on the waterproofing of their plumage and how much of their skin became wetted. Completely waterproof ducklings, which maintained a layer of air between their skin and the water, lost heat slowly, but poorly waterproofed birds with wet skins lost heat quickly. Waterproofing was reduced in the laboratory when the ducklings' feathers became soiled and disarranged and when one swam in soapy water.
SOME ASPECTS OF TAXONOMY AND RELATIONSHIPS OF BARBETS (CAPITONIDAE)
Authors: Goodwin Derek
Published: April 2008

Some aspects of the taxonomy and relationships of the barbets are discussed and illustrated, with special reference to the recent classifications of the family by Ripley and by Peters. The colour pattern of the head appears to function as a species‐specific recognition mark. Sympatric species of similar size usually differ strikingly in head colouration. There are several examples of apparent character displacement. The genus Psilopogon is considered to be closely allied to Megalaima. Megalaima lagrandieri forms a link between the two genera. The resemblances between Calorhamphus and Gymnobucco are due to convergence. The latter genus is very closely related to the species placed in Stactolaema. Lybius chaplini is thought to be closer to L. rubrifacies than to L. leucocephalus. The mobility of the rictal bristles of a living Megalaima asiatica is described.
THE REPRODUCTIVE BEHAVIOUR AND TAXONOMY OF HEMPRICH'S GULL LARUS HEMPRICHI
Authors: Fogden M. P. L.
Published: April 2008

Observations were made in the sea bird colonies of the Kiunga Archipelago in Kenya, in 1961. The islands are described and the numbers of the five species of sea birds (one gull and four species of terns) which were found breeding on the islands visited are recorded. The principal predators in the colonies are man and Hemprich's Gull Larus hemprichi.

Particular attention was paid to the reproductive behaviour of hemprichi which is a tropical hooded gull with extensive areas of dark plumage. Dark plumage in gulls is disadvantageous to plunge‐diving for fish; hemprichi is almost entirely a scavenger.

Hemprichi is not a social breeder and as a rule there is only one pair on each island. It is also relatively non‐territorial.

In the most recent revision of the Laridae, hemprichi is classified as a “‘primitive’ hooded gull”, but in fact its behaviour complex is not characteristic of this group. The displays of hemprichi are described and compared in detail with the homologous displays of “primitive” hooded gulls, masked gulls and the large white‐headed gulls in the taxonomic sense.

These displays are all except one (Facing Away) very similar to those of the Herring Gull L. argentatus (a large white‐headed gull). By treating the displays as taxonomic characters, it is concluded that hemprichi is a large white‐headed gull which has acquired a hood and dark plumage, this change being facilitated by its having become a scavenger (and thus not dependent upon white plumage as an adaptation to plunge‐diving), and by some other factor possibly connected with tropical insolation.

Evidence is put forward which shows that the White‐eyed Gull L. leucopthalmus, another tropical hooded gull superficially similar to hemprichi, is also a large white‐headed gull.
LIFE HISTORY OF THE BLUE‐DIADEMED MOTMOT MOMOTUS MOMOTA
Authors: Skutch Alexander F.
Published: April 2008

Over a wide geographical and altitudinal range, extending from sea level up to at least 7,000 feet in Costa Rica, the Blue‐diademed Motmot has adopted a great variety of habitats.

It lives in pairs through most, if not all, of the year.

Its food consists of a variety of insects, especially beetles, and small fruits.

Pairs or trios apparently engaged in courtship hold pieces of green leaf or other fragments of vegetation in their bills, although they never take such material into their nests.

Nesting burrows, up to 7 feet long, are usually dug from the side of a hole in the ground, rarely in an exposed bank where the entrance is conspicuous. Excavation begins in the wet season, from late August to October, and may continue for 21/2 months, chiefly in the late morning and early afternoon, when the soil is driest, at an average rate of little over one inch per day. Until the beginning of nesting at the end of the following dry season, the burrow is not used for sleeping and is rarely visited.

In March or April, three white eggs are laid on the bare floor of the nest chamber. Both sexes incubate. One enters the burrow soon after noon and stays until the following dawn. After 15–30 minutes the mate enters and sits for about seven hours. The incubation period is about three weeks.

The nestlings hatch completely naked. The nestling period is 29–32 (once 38) days. Brooding, even at night, ceases before the young are a week old, although they are still naked. Both parents bring them a variety of insects, chiefly beetles, small fruits, and occasionally a small snake, lizard, or bird. At one nest the rate of feeding increased up to the nestlings' nineteenth day, when each was fed 2·3 times per hour.

After the nestlings' departure, neither parents nor young sleep in the burrow. The species is single‐brooded in Costa Rica.
THE BIRDS OF THE DAHLAC ARCHIPELAGO
Authors: Clapham C. S.
Published: April 2008

The Dahlac Archipelago, in the southern Red Sea, is described. Eighteen of its islands were visited by an expedition in August and September 1962, and 33 species, excluding migrants, were recorded. The distribution of these species between islands is summarized (Table 2), and observations are made on their habits, habitats, food, and liability to predation. Evidence of breeding is given for Sula leucogaster, Falco concolor, Larus hemprichi, L. leucopthalmus, Sterna bengalensis and Sauropatis Moris; breeding is also suggested for five further species.

Particular attention is paid to Falco concolor, and existing knowledge of this species is summarized. Information is given about breeding biology, food, hunting methods, call and other habits, and the species is compared with F. eleonorae, from which it differs chiefly in the absence of colonial breeding.

The breeding biology of Sula leucogaster is briefly discussed, and attention is paid to the differences between Larus leucopthalmus and L. hemprichi.
DISTANCE NAVIGATION IN THE ADELIE PENGUIN
Authors: Emlen J. T. , Penney R. L.
Published: April 2008

Male Adelie penguins Pygoscelis adeliae were transported from coastal rookeries in the Ross Sea area of Antarctica to three release points on featureless ice plateaux in the interior of the continent. Birds were released individually and their departure routes mapped for distances of 2–4 km., the position of the bird being determined by triangulation every five minutes. Precise data were thus obtained on the straightness of course and direction selected by each of 103 birds.

Birds released inland from a coastal rookery under favourable conditions consistently moved in straight courses N.N.E. toward the coast. Birds from the same rookery released at points to the east and west took courses essentially parallel to this departure direction, i.e., northwest and northeast respectively on a meridian scale rather than true north or in the homeward direction. These and other experiments under varying degrees of cloud cover and with birds prepared under artificial day‐night light regimes indicate that the birds possessed a navigation mechanism which used the sun as the primary orientation cue plus a biological clock to compensate for changing sun azimuth positions. The mechanism effected a consistent escape direction for birds of a given population (source) regardless of the location of the release site.

The “grid N.N.E.” orientation of these birds is compared with “nonsense orientation” as described for ducks and other birds. It is considered to have survival value in the present instance in steering lost penguins to the appropriate off‐coast feeding areas and in segregating and concentrating the birds from the various circum‐continental populations.
FEEDING ECOLOGY OF THE BLACK‐FACED DIOCHQUELEA QUELEAIN NIGERIA
Authors: Ward P.
Published: April 2008

The results of a three‐year study of the diet ofQuelea queleain the Lake Chad region of Nigeria indicate why this bird periodically does extensive damage to crops of dry‐season guinea‐corn.

The normal food of the birds in the early dry‐season consists of small grass seeds collected off the ground. As the supply of these diminishes there is a gradual change‐over to larger seeds.

In years when this change begins early, it is liable to coincide with the ripening of the cereal crop and severe damage may be caused.

At the beginning of the rains the dry‐season food supply is lost owing to the simultaneous germination of the seeds over large areas.

The birds lay down fat reserves in preparation for this lean period.

After a short time the birds migrate south to regions where rain has been falling for some weeks.

In the short period spent in these parts, Queleas feed on ripening grass seeds—including those of cultivated millet.

There is evidence for considerable mortality during this time of food scarcity and it is suggested that the numbers of Queleas are limited by the food supply.

The significance of communal roosting is discussed. It is proposed that the phenomenon is related to food finding, the roost being considered as an “information centre” for the large area prospected by the birds constituting the roosting community. A method is outlined by which information on food availability within the feeding area may feasibly be transmitted within the community.
DETECTION BY RADAR OF AUTUMN MIGRATION IN EASTERN SCOTLAND
Authors: Wilcock John
Published: April 2008

Radar observations through one autumn in Aberdeenshire are described showing that more migration takes place in anticyclonic weather than transitional weather, and even less migration takes place in disturbed weather. More migration is detected by radar with following winds than with opposed winds.

Comparison of data collected in Norfolk and Aberdeenshire during one season at each shows that more migration is detected by radar in Norfolk, and westward movements, which are a feature of migration into Norfolk, appear in Aberdeenshire only when birds are first drifted northwards.

Dawn ascent and reorientation movements of birds in the northern North Sea are described, showing that changes in heading were consistently between S.W./S.S.W. and S.S.E. during the autumn studied.

Weather data, radar data and ground observer data from Aberdeenshire and the Isle of May Bird Observatory were analyzed and show again that the normal migration pattern is to fly high with following winds and low only with opposing winds as in Norfolk. However, the weather in Aberdeenshire was more disturbed than it had been in Norfolk, with the consequence that weather factors, other than wind, which affect the normal migration pattérn were found to be much more common.
MIGRATION ACROSS THE MEDITERRANEAN OBSERVED BY RADAR
Authors: Casement M. B.
Published: April 2008

Bird migration across the Mediterranean was studied by radar from an aircraft carrier for brief periods during the springs of 1961, 1962 and 1963 and in the autumn of 1963.

The radar displays were photographed and analysed to give intensity (scales 0 to 6) and tracks have been plotted on the accompanying Maps together with Tables setting out the weather data and records of bird sightings. Most echoes that could be measured were between 4,000 and 6,000 ft. Small (passerine) echoes usually moved at 20–30 knots, large ones (presumed to be waders, ducks, etc.) at up to 47 knots.

The analyses of each of the nine sets of observations are discussed in detail from the Atlantic to the south of Crete, including the Aegean. There is clear evidence, within the limitations of the stated methods used and the dates of observations, that migration takes place along the whole length of the Mediterranean at almost uniform density except across the Ionian Sea, where it is greatly reduced. This is possibly because the long desert crossing and the long sea crossing are separated by only a very narrow coastal strip of vegetation and there is obvious survival value in crossing further east or west. There is no evidence for concentration across the Sicilian narrows, through Malta or across the Straits of Gibraltar. The direction of migration west of the Ionian Sea is N.E./S.W. and to the east is N.N.W./S.S.E.

A large‐scale movement was observed coasting 20 miles offshore from Portugal in autumn tracking S.W. off Cape St. Vincent. This area in particular deserves further investigation as also does the area south of Crete.

Migration is considerable at least from 18 August‐24 October. The main departure of small migrants from land starts 40–50 minutes after sunset and tails off with the dawn. The diurnal pattern of intensity observed at sea is noted and it is suggested that the shape of the build‐up and the time of the peak can provide a clue as to the point of departure. There are indications that in spring, especially south of Crete, some migrants do not rest in the narrow coastal strip but cross the Sahara Desert and the Mediterranean Sea non‐stop.

The significance of the results is discussed in the light of further visual observations made in 1964 and 1965.
AUTUMN AND SPRING WEIGHTS OF SOME PALAEARCTIC MIGRANTS IN CENTRAL NIGERIA
Authors: Smith V. W.
Published: April 2008

During the winters 1963/64 and 1964/65 some 700 weights of 19 species of Palaearctic migrants caught in Central Nigeria were obtained. Where there were adequate weights for analysis, mean weights in the spring were significantly heavier than mean autumn weights; mean weight gains in the spring varied from 47% (Pied Flycatcher) to 21% (Garden Warbler and Spotted Flycatcher). Individual gains were higher.
BREEDING BIOLOGY OF THE MANX SHEARWATER PUFFINUS PUFFINUS
Authors: Harris M. P.
Published: April 2008

Studies on the breeding biology of Puffinus puffinus were carried out in 1963 and 1964 at the large colony on Skokholm, Wales.

During the six weeks before laying the birds spent up to a quarter of the days in the burrows, but the ten days immediately prior to laying were normally spent at sea.

There is a prolonged laying period, with a marked peak in the first half of May. Details are given of a second egg being laid when the first was deserted immediately after being laid.

The male took the first incubation spell. The incubation spells ranged from one to 26 days and averaged six. The incubation period was about 51 days. The frequency of visits to land by breeding birds, unlike those by non‐breeders, was not affected by the moon.

On hatching, the chicks grew rapidly and reached maximum weights of between 505 and 755 gm. sometime between 39 and 61 days. There was a variable desertion period, usually eight or nine days, before the chicks left the island about 70 days after hatching. During the feeding period the chick received about two feeds every three days. There is evidence that adults visited the chicks more frequently than this. There was no correlation between growth of the chicks, their feeding rates or fledging weights and the time of laying.

There was a high survival (about 95 %) of chicks during the fledging period but some eggs were lost in disputes for burrows.

Nine pairs in 1964 were unable to raise two young simultaneously. Parents altered their feeding rhythms to try to feed two young but did not themselves lose weight.

It is suggested that the critical factor in the production of young is the availability of food for the young immediately after they leave the colonies.
OBSERVATIONS ON THE BEHAVIOUR AND ECOLOGY OF THE FLIGHTLESS CORMORANT NANNOPTERUM HARRISI
Authors: Snow Barbara K.
Published: April 2008

From 25 September to 8 October 1963 daily observations were made on a group of Flightless Cormorants Nannopterum harrisi nesting on the west side of Albemarle Island in the Galápagos.

Flightless Cormorants are apparently bottom‐feeders, and confined to shallow coasts at the western end of the Galapagos Archipelago where there is an upwelling of cold nutrient‐rich water. There is no reason to suppose that they are declining in numbers.

Males are very much larger than females, the size difference between the sexes being greater than in other species of cormorants.

Courtship behaviour, nest‐building and mating are described. The earliest phases of courtship take place on the water, later phases at the nest‐site. Homologies are traced with other cormorant species. In contrast to other members of the family, allopreening apparently does not occur.

Both sexes incubate and care for the young. Observations on families of different ages over the 12‐day period allowed the development of the young to be traced up to the age of about 40 days.

Egg‐laying takes place in most months of the year, with a peak in April‐June and perhaps a second peak about October. Observations on birds colour‐ringed on an earlier visit suggested that individuals do not breed more than once in the year. Nesting success appeared to be very low in 1963.
NOTES ON THE ECOLOGY OF THE CATTLE EGRET ARDEOLA IBIS AT ROKUPR, SIERRA LEONE
Authors: Craufurd R. Q.
Published: April 2008

SUMMARY

The Cattle Egret is a dry season visitor to Rokupr in Sierra Leone during the bird's non‐breeding season. There are no cattle in the area to attract the herons and they obtain nearly all their food from small isolated areas of vegetable gardens which are associated with all the villages. The number of herons associated with each garden is closely correlated with the area of that garden and is about two birds per acre.

The daily life of the birds is discussed, in particular the pre‐roosting assemblies and the flight to roost, and it is shown that each flock leaves for the roost at the same time each day, about 30–35 min. before dusk.

Observations made at a particular roost showed that all the Cattle Egrets reached the roost before dusk and from these observations, combined with those made on the feeding grounds, it is concluded that the number of Cattle Egrets using the roost is determined by the number and area of the feeding grounds that lie within 30–35 minutes flying time (about 12 miles) of the roost.

Other species using the roost are briefly discussed.
SUBFOSSIL PETREL BONES FROM THE CHATHAM ISLANDS
Authors: Bourne W. R. P.
Published: April 2008

The breeding community of petrels on the Chatham Islands has previously seemed curiously poor compared to that of analogous stations in the Indian Ocean or South Atlantic (14 species compared with 18 in the Tristan‐Gough group). Examination of subfossil deposits from the Chatham Islands probably dating from the early stages of human colonization which occurred within the last few hundred years reveals remains of at least 20 petrels, all of which except one may well have bred in the past, without including storm petrels, of which two species are still known to breed while others may also have bred in the past. The grand total of at least 21 breeding species, many apparently in vast numbers, would probably make the archipelago the most important breeding station for petrels in the world at the time of the first human colonization. It seems possible that in addition to the present breeding species the following may have bred: at least one endemic species of gadfly petrel, the Magenta Petrel Pterodroma magentae, and local populations of at least two other gadfly petrels, two shearwaters of the genus Procellaria and two of the genus Puffinus and a sooty albatross of the genus Phoebetria. Small populations of these, and perhaps other undetected species as well, may still survive in inaccessible places.
OBSERVATIONS ON THE BEHAVIOUR OF THE HAMERKOP SCOPUS UMBRETTA IN UGANDA
Authors: Kahl M. P.
Published: April 2008

Hamerkops were studied in Uganda, mainly in the vicinity of Kampala, during January‐August 1964. Behavioural observations were made of nest‐building pairs, as well as of non‐breeding birds.

Locomotion and feeding behaviour are described. Diving take‐offs and landings, essential for entering or leaving a completed nest, are sometimes seen in other situations as well. Birds sometimes forage while on the wing, in addition to the more usual method while wading.

The most frequently seen comfort movements and maintenance activities are described. Hamerkops do not excrete onto their legs when over‐heated as do the storks. The resting posture of sitting completely down on horizontal branches, which is common among Hamerkops, apparently is not known in any of the herons or storks.

Primarily hostile (Upright and Forward Threat) and primarily sexual (“Yip‐purr”, Nodding and False Mounting) social displays are described. During False Mounting, birds mount their partners repeatedly without making any attempt at copulation; reverse mountings, in which the other partner assumes the top position, are frequent.

The large, hollow nest and its construction are briefly described. During the 6–7 week building period at one nest, at least 8000 loads of material were added to the structure. Both members have an equal role in nest‐building, and generally work independently of each other. They showed no stick‐exchange displays as do herons and storks.

When all known aspects of the Hamerkop's behaviour are considered, there appears to be little similarity with either the herons or the storks. In fact, present behavioural evidence does not seem to indicate a particularly close relationship with any other birds so far studied.
LONG‐DISTANCE VAGRANCY IN THE PETRELS
Authors: Bourne W. R. P.
Published: April 2008

The records of long‐distance vagrancy in the Procellariiformes are listed and re‐examined. Some are clearly valid, more are obviously doubtful, many are difficult to confirm. Some records from the last century have failed to be repeated in this, but others have been repeated, sometimes more frequently. Some of them suggest hitherto unrecognized migrations or post‐juvenile or post‐breeding dispersal. Otherwise in general it appears that the more migratory albatrosses and much less often perhaps the southern fulmars may cross the equator into the opposite hemisphere, shearwaters and storm‐petrels may go astray on migration into the wrong ocean, and the gadfly petrels of the genus Pterodroma, though rarely recorded anywhere near land away from the breeding stations, are occasionally capable of prodigious feats of wandering across several oceans and continents. These last records are hard to explain, though some at least must be genuine; the best explanation appears to be that the birds are first displaced from their range by storms, and then have vast powers of endurance so that they are able to wander even further afield in attempting to return to it. They then often come to grief in circumstances where it may be very hard indeed to prove the manner of the appearance beyond all reasonable doubt, and there will always be a large element of uncertainty about many older records, including a number on current national lists, although many cannot be ignored entirely.
SOME ECOLOGICAL ASPECTS OF THE FEEDING BEHAVIOUR OF THE OYSTERCATCHER HAEMATOPUS OSTRALEGUS ON THE EDIBLE MUSSEL MYTILUS EDULIS
Authors: Norton‐Griffiths M.
Published: April 2008

Oystercatchers have two methods of opening mussels, both neatly adapted to the structure of the prey. To open mussels exposed by the tide, the bird hammers a hole along the ventral margin of the shell, whereas to open mussels under water, the bird drives its bill into the gape of the valves to cut through the posterior adductor muscle. Large and strong‐shelled mussels can be opened by stabbing but not by hammering.

Feeding methods of Oystercatchers vary from mussel‐bed to mussel‐bed. These variations in behaviour are attributable to differences in the strength of the shells of the prey and to the firmness of their attachment to the substrate.

Diversity of ecological conditions on the mussel‐beds causes an apparent size selection of prey by Oystercatchera.
ORIGIN OF THE AVIFAUNA OF URBAN AND SUBURBAN SINGAPORE
Authors: Ward Peter
Published: April 2008

A list of the commoner garden and town birds of the tropical city of Singapore is given. None of them are birds of the rain forest which formerly covered the island. The majority are coastal species the natural habitats of which were mangrove and the thin fringe of savanna along parts of the east coast of the Malayan Peninsula. The reasons for this are discussed.

The number of garden species is comparatively small and many niches appear to be vacant. These are expected to be filled mainly by open country species moving down the peninsula from Burma and Thailand along the corridors being opened up by deforestation. This process has already begun, though few species have yet reached as far south as Singapore.

The garden avifauna is unstable and numerous changes in status have occurred in the last few decades; many more are predicted.
CLUTCH‐SIZE, INCUBATION AND HATCHING SUCCESS IN THE HOUSE SPARROW AND TREE SPARROW PASSER SPP. AT OXFORD
Authors: Seel D. C.
Published: April 2008

Clutch‐size, incubation and hatching success were studied in P. domesticus and P. montanus in 1961 and 1963–64 at Oxford. The most frequent clutch‐size was four eggs in P. domesticus and five eggs in P. montanus. With one exception, colonies of P. domesticus showed no significant annual or local variations in its mean clutch‐size; in P. montanus, however, there were significant annual variations in the mean clutch‐size. Both species showed a seasonal increase followed by a decrease in their mean clutch‐sizes.

Partial incubation occurred during the laying period of the clutch; sufficient incubation for continuous development of the embryo was apparently achieved when the last egg had been laid in clutches of two and three eggs in P. domesticus and in clutches of four eggs in P. montanus, but when the penultimate egg had been laid in larger clutches of both species. On average, hatching in P. domesticus occurred more or less synchronously in all eggs in clutches of two and three eggs, and in all eggs except the last one laid in larger clutches; the last egg in the larger clutches hatched up to a day after the others. It is suggested that this pattern of hatching was brought about by the pattern of incubation during the laying period.

P. domesticus had a lower hatching success than P. montanus, probably because fewer of its eggs were fertile.