bluuebunny/crossref_metadata_2025 huggingface dataset:
ROOSTING MOVEMENTS OF BIRDS AND MIGRATION DEPARTURES FROM ROOSTS AS SEEN BY RADAR
Authors: Harper W. G.
Published: April 2008

Unusual radar echoes attributable to the roosting movements of large flocks of birds, and to departures from roosts on migration flight are illustrated. Probably the most striking displays are received from Starlings Sturnus vulgaris. Radar evidence is shown of a much more rapid break‐up of flocks on migration at night than by day. Weather at departure points is studied.
MIGRATION ACROSS THE NORTH SEA STUDIED BY RADAR PART 1. SURVEY THROUGH THE YEAR
Authors: Lack David
Published: April 2008

Migration across the North Sea off Norfolk is reviewed over three years on the basis of the detection of bird echoes by radar.

Large movements are most frequent in March, April and November and least frequent in December and January.

Most movements are east between January and May, west in June and July, and west or southwest during the rest of the year, while there is also a small passage northwest in spring and southeast in autumn.

Occasional movements were observed southwest in March in cold weather, west in spring during eastward emigrations with fog or rain at sea, also a presumed drift‐migration northwest in March and possibly southwest in September, with subsequent redetermined movements heading southeast and east respectively.

The chief additions to existing knowledge based on visual evidence are (a) the huge eastward emigrations in spring, (b) the arrivals southwest, presumably direct from Scandinavia, in late autumn and (c) the presumed redetermined movements eastward after drifted arrivals.

The limicoline species in June and July, and the passerine species in late autumn, cross the North Sea primarily with easterly winds and hardly at all with westerly winds, whereas in spring they often set out against the wind. This might merely be due to a stronger migratory urge in spring than autumn, but it also seems possible that westerly winds deter migration in autumn because they are so often associated with rain and other unfavourable conditions.
RECENT EXPERIMENTS ON BIRD ORIENTATION
Authors: Kramer Gustav
Published: April 2008

Pigeons raised in open aviaries show homeward orientation when released 100 or 150 km. away from their home aviary. Some of them (15–20%) actually return.

When palisades are placed around the aviaries orientation vanishes. The palisades allow the birds free sight of the sky except for a zone of an elevation of 3° above horizon.

Orientation is absent also in pigeons raised in an aviary giving view of a broad sector to the north, i.e. the direction opposite to release. These experiments are being continued.

Homing pigeons were subjected to an artificial light/dark change (period 24 hours). If the artificial cycle was out of phase with the natural day/night cycle, the “internal clock” was shifted within three to four days as shown by directional responses.

Basically the same deviations are shown by “shifted” pigeons taken away from home and released. What appears to be influenced by shifting is a directional response which must necessarily rest upon a previous determination of position relative to home. This preceding part of the whole orientation performance appears to be unaffected.

Orientation is influenced by spatial factors, or factors related to space, of unknown nature. The observed phenomena may be tentatively subdivided into variations due to direction, site of release place, site of loft, and region.

Among weather conditions, cloud cover has a significant influence upon homing orientation. Top‐class homing flights are less frequent with overcast.

Homing ability is subject to an annual fluctuation. Homing is best in August and poorest in January. Parallelity to temperature is obvious throughout the year. Correlation between particular releases and temperatures prevailing at the particular occasions exists only in autumn and winter but not during the rest of the year.

A correlation has also been found with interdiurnal barometric change. This correlation is scarcely perceptible at surface level, but significant at the 500 and 200‐mb. level. This correlation concerns homing performance as well as correctness of departure directions, but not scatter of departures.

So far no cross relations can be established between results attained with the different ways of approach.

It is thought that homing ability as shown by the domestic pigeon continues to be a problem of ornithological interest. It is assumed the same ability is possessed by wild species.
THE CONTROL OF POPULATION‐DENSITY THROUGH SOCIAL BEHAVIOUR: A HYPOTHESIS
Authors: Wynne‐Edwards V. C.
Published: April 2008

Any given species of animal generally occurs at a higher population‐density where food is more plentiful, and vice versa; quantitative evidence points to a rather close correlation between the two. Such density differences arise from the activities of the animals themselves, and this implies that population‐density is subject to effective internal control, i.e., it is self‐regulating.

A theory is put forward that, for each species, population‐densities are limited at a safe level, which will protect the food‐supply from long‐term depletion and assure its renewal for the future. Instead of competing directly for food, animals compete for conventional substitutes, e.g. territory or social position, which are capable of imposing a ceiling density at the optimum level, and can prevent it from rising to the starvation level which would endanger future resources.

Such limitation by conventional means requires the existence of a social organisation. Forms of social competition supplant direct competition for food; their intensity is density‐dependent and provides the animals with an index of population‐density. This index serves as the “feed‐back” for the machinery of density‐adjustment, which operates, very broadly, through (1) direct movement (emigration/immigration), and (2) varying the birth and survival rates.
THE HOUSE SPARROW PASSER DOMESTICUS: POPULATION PROBLEMS
Authors: Summers‐Smith D.
Published: April 2008

Two problems of House Sparrow populations are examined: the influence of habitat on numbers and the variation in a population of House Sparrows throughout the year. Available data on censuses in Great Britain enable the population to be estimated as 10 millions; censuses from several parts of the bird's range suggest that House Sparrow numbers are correlated with the human population, the ratio being 1: 5. The seasonal variation in composition of a population is estimated from observations over five years on House Sparrows breeding on a group of seventeen houses together with breeding and mortality data obtained from British Trust for Ornithology records. The population reaches a maximum at the end of July when it is slightly less than double that at the beginning of the breeding season. It is considered that numbers are controlled by food supply and the colonial behaviour of the bird.
MIGRATION ACROSS THE NORTH SEA STUDIED BY RADAR PART 2. THE SPRING DEPARTURE 1956–59
Authors: LACK DAVID
Published: April 2008

1. Radar observations on the eastward emigration of winter visitors across the North Sea from East Anglia were analysed from 24 February to late April in four years.

2. Bird‐echoes were most numerous around 21.00 hours, with a second smaller peak an hour after dawn. Occasionally, emigration continued throughout the 24 hours.

3. The volume of emigration was influenced by (a) the internal state of the bird, (b) temperature, (c) wind‐speed, (d) rain and cloud; it was not influenced by barometric pressure, the general weather situation, or the direction of the wind as such.

4. In very similar cold weather 6–13 April, there was much more emigration in 1958, after a long hold‐up, than in 1957 after much previous emigration.

5. There was more emigration in warm than cold weather in February and March, but not in April or May. The threshold temperature required was higher in February than March. A marked rise or fall in temperature had no immediate effect.

6. Morning migration was visible from the ground with opposed but not with following winds.

7. Most height; obtained by radar were below 5000 feet, but the highest at night were not infrequently at 13,000 feet.

8. The track over the sea was normally the resultant between the bird's heading and the wind, the track nearly always being north of east with a southerly wind and south of east with a northerly wind. The bird maintains its sense of direction, but apparently not its sense of position, in flight over the North Ses.

9. The migrants' mean heading varied on different days between N.E. and rather south of E.S.E., while occasionally two eastward emigrations proceeded simultaneously on mean headings differing by some 25.

10. Under totally overcast conditions, migrants flew at random. This means that they would gradually drift with the wind.

11. Observations on Starling flocks are described.
THE EFFECT OF AGE AND DENSITY OF BREEDING BIRDS ON THE TIME OF BREEDING OF THE KimWAKE RISSA TRIDACTYLA
Authors: WHITE J. C. COULSON & E.
Published: April 2008

1. Differences were recorded in the time of breeding of colonies of the Kittiwake at Marsden, Co. Durham, between 1951 and 1958 inclusive. During 1958, observations were extended to other colonies in northeast England and southeast Scotland.

2. Females breeding for the first time bred 9–8 days later than those breeding for at least the fourth time.

3. The age composition of the Marsden Kittiwake colonies has been estimated. The old, established, colonies always had less than 25% of the birds breeding for the first time, while the younger colonies had much higher proportions of young birds.

4. The age‐compositions of the colonies and the time of breeding of birds according to previous breeding experience did not account for the differences found in the time of breeding of the colonies.

5. The time of breeding was directly related to the density of breeding birds, particularly those within a radius of 5 feet of the nest.

6. The maximum nest‐density was usually related to the rock structure, but in one colony the maximum density was probably determined by the minimum distance at which Kirtiwakes can tolerate their neighbours.

7. The time of return to the colonies also appeared to be related to density and this suggested that the effects produced by the density of breeding birds was carried over from one year to the next.

8. All the Kittiwake colonies studied completed breeding at about the same time but differed in the time that breeding commenced. The spread of breeding was apparently related to the range of densities within the colony concerned.

9. It is suggested that the onset, spread and completion of breeding within a colony can be explained by the maximum density, the range in density and the presence of low‐density areas in all colonies.

10. The “socia‘ stimulation” apparently operating in the Kittiwake colonies differed from that envisaged by Darling; the effective distance appeared to be short (5 feet) and tended to produce a longer breeding season.
VARIATION IN THE AFRICAN BLACK TITS, PARUS NIGER AND PARUS LEUCOMELAS
Authors: HALL B. P.
Published: April 2008

1. The relationship between the Black and Grey Tits of Africa is discussed briefly.

2. Variable characters in the Black Tit are listed, on which five forms can be distinguished.

3. The characters, ranges and ecology of the five forms are set out, with some discussion on atypical populations within the forms, and on the variable population of central and southeastern Uganda.

4. It is concluded that speciation is taking place in many populations of Black Tits and that this presents considerable difficulties in assessing the relationship between forms.

5. Reasons are given for considering P. n. niger and P. n. carpi as specifically distinct from other forms. The question of whether guineensis should be considered specifically distinct from P. I. leucomelas and P. I. insignis is left open until more is known of their field characters in Uganda and Abyssinia. Similarly purpurascens is regarded as a variable race until more field study has been done.
THE PASSAGE OF PALAEARCTIC MIGRANTS THROUGH ERITREA
Authors: SMITH K. D.
Published: April 2008

The vegetation and climate of Eritrea arc described, and passage migrants and winter visitors are listed according to status and altitudinal range.
THE BREEDING BIOLOGY OF THE SHAG PHALACROCORAX ARISTOTELIS ON THE ISLAND OF LUNDY, BRISTOL CHANNEL
Authors: SNOW BARBARA
Published: April 2008

1. In the 4 years 1454–1957 the breeding population of Shags on Lundy appeared to he static. Most of the nest‐sites were used each year. Mortality was deduced from the re‐use of old nest‐sites and the return of colour‐marked birds.

2. Most of the clutches were started during a period of 3 to 4 weeks in each year but dates varied by as much as 1 6 days in different years.

3. Different types of ncst‐site and nest‐material are used on different parts of the island. Larger nests were more successful than smaller ones.

4. The mean‐clutch size for the five years 1954–1958 was 307, varying annually by us much as 0–4 egg. Clutch‐size decreases with the advance of the season.

5. Incubation starts with the second egg in c/3 but a day or more later in c/4.

6. Hatching success 1954–1957 varied only between 69 and 73%. Infertility was the mam cause of hatching failure.

7. Eggs were weighed and measured in 1957 and 1958. In each year the larger clutches contained larger eggs than the smaller clutches. The mean weight of eggs was greater in 1957 (when clutches were bigger) than in 1958. This was due to a higher specific gravity.

8. Fledging success was 90–95%, except in 1956 when it was 67%. The heavier losses in this year appeared to be due to food shortage. Most chick losses occur in the first ten days.

9. The growth of chicks was studied in 1957. Male chicks can frequently be differentiated when 30 days old by their heavier weights. The fourth chick in a brood is normally below average weight during the first half of the fledging period.

10. Some marked juveniles remain on the island up to 50 days after leaving the nest. During this time they show partial dependence on their parents.

11. Later clutches are less successful than early clutches. Nests situated on narrow cliff ledges were less successful than nests at other sites.
THE ZOO‐GEOGRAPHICAL AFFINITIES OF THE AVIFAUNA OF THE WESTERN CAPE PROVINCE
Authors: WINTERBOTTOM J. M.
Published: April 2008

The area considered here is that part of South Africa south of the Orange River and west of the eastern borders of Mossel Bay, Oudtshoorn, Prince Albert, Beaufort West, Victoria West, Richmond, De Aar and Philipstown.

It is considered to fall into three avifaunal divisions, winter‐rainfall area, temperate forest, and karoo.

The affinities of the first and last of these are with the Southwest Arid zone; that of the second, which exists only ii isolated patches surrounded by winter‐rainfall vegetation, with the East Coast.

No valid grounds exist for sub‐dividing the karoo into smaller areas.

Examples arc given of changes of range in recent years.
THE NEST AS A DORMITORY
Authors: Skutch Alexander F.
Published: April 2008

As a rule, only birds which breed in roofed nests or those built in enclosed spaces sleep in their nests when not incubating or brooding young. The chief exceptions are rails, coots, and gallinulse, which build platforms to raise them above the water or wet ground while they sleep, and Curved‐billed Thrashers, which roost on open nests in thorny cacti.

The first step in the evolution of the dormitory habit appears to be sleeping in the covered breeding nest itself before the eggs are laid or after the fledglings depart. In the simplest case, only one parent occupies the breeding nest. But in a number of species, the second parent uses the nest as a dormitory even while it contains eggs and nestlings, and sometimes unmated helpers roost with the parents. A further advance is made when the fledglings are led to sleep in the nest they have just left.

The next advance is the construction of special dormitories, not intended for eggs. These usually resemble the breeding nest, but differences in form or site are sometimes found, especially in tropical wrens. Only birds which make or acquire dormitories, in addition to their breeding nests, are likely to enjoy such lodges through the year. In them, self‐supporting individuals may sleep singly, or in pairs, or with their dependent offspring. In the final stage of the evolution of the dormitory habit, the young lodge with their parents long after they are self‐supporting. Often each family remains separate throughout the year; but sometimes, probably in consequence of the loss of dormitories, several families club together in the non‐breeding season. Numerous examples of each of the foregoing arrangements are given.

In a harsh environment, as at high latitudes and above timberline on tropical mountains, many birds seek closed spaces for sleeping, and their lives may depend on the availability of such protection. Nevertheless, the dormitory habit is best developed in mild climates where the birds are permanently resident.
ZUGUNRUHE ACTIVITY IN CASTRATED BRAMBLINGS FRINGILLA MONTIFRINGILLA
Authors: Lofts B. , Marshall A. J.
Published: April 2008

1. Zugunruhe, a condition of nocturnal activity in caged migratory birds that is generally held to be identical to premigratory restlessness in the wild, developed in the spring in captive castrated male Bramblings Fringilla montifringilla.

2. Zugunruhe occurred in intact control birds about a week before it was recorded in castrates. Intact birds became restless each evening earlier than did the castrates.

3. Nevertheless, the peaks of intensity in both castrate and intact birds occurred at the same time and coincided with the period during which the bulk of the wild population migrated to their northern breeding grounds.

4. In intact birds Zugunruhe occurred during the initial period of seasonal gonad modification. It waned by the time of sperm‐production when, under wild conditions, the birds would have completed their journey to their distant breeding grounds.

5. The data suggest that the seasonal phenomena of migratory unrest and gonad development occur independently of each other. The remote possibility that migration is influenced by extra‐testicular androgens is mentioned.
NOTES ON THE BIRDS OF ANNOBON AND OTHER ISLANDS IN THE GULF OF GUINEA
Authors: Fry C. H.
Published: April 2008

1. A systematic list of the birds of Annobon Island in the Gulf of Guinea is presented with field notes obtained on a recent expedition, and the records are compared with those of previous ornithological visits.

2. The land avifauna of Annobon has altered markedly in the last five or six decades. That the resident land‐birds provide severe competition for newly arrived immigrants is offered as the most plausible reason for the paucity of land‐birds species on the island.

3. Brief ornithological notes from Sao Tom and Fernando Po are given as addenda to recent papers on the respective avifaunas.
THE ORIENTATION OF PECKING IN VERY YOUNG MAGPIE GEESE ANSERANAS SEMIPALMATA
Authors: Davies S. J. J. F.
Published: April 2008

The goslings of the Magpie Goose Anseranas semipalmata make co‐ordinated pecks about 40 min. after hatching. The intensity of pecking is greater by day than by night and also increases with increasing age in unfed goslings. In a series of experiments goslings tended to orientate their pecks towards high, light, green and yellow objects rather than low, dark, blue or red ones, but did not discriminate between rough and smooth objects. It is suggested that these generalized orientation tendencies suffice to direct the goslings' pecks towards potential food, the seed heads of swamp plants. A more precise innate orientation, such as is found in some gull chicks, would not confer greater protection from predation than the shelter of the breeding swamp itself provides, and might prevent the goslings from exploiting some of the available food.
MIGRATION FROM MOROCCO INTO SOUTHWEST SPAIN IN RELATION TO WEATHER
Authors: Nisbet I. C. T. , Evans P. R. , Feeny P. P.
Published: April 2008

“We must not, I think, deny migration in general: because migration certainly does subsist in certain places, as my brother in Andalusia has fully informed me. Of the motions of these birds he has ocular demonstration”.–Gilbert White, 12 February 1771.

1. Migration was stuaied on the south coast of Spain between Gibraltar and Huelva during five successive springs. Systematic observations were made during a total of 11 weeks by four parties, and casual observations made by other observers have also been used.

2. West of Cape Trafalgar, grounded passerine night migrants were seen in numbers only during east winds. Observations of birds crossing the moon indicated that this correlation was due to drift, and that in the absence of east winds many more birds pass over the Straits of Gibraltar than over the wider stretch of sea to the west, probably after diversion towards the Straits by the west coast of Morocco.

3. The mean heading of nocturnal migrants seen crossing the moon at the Straits of Gibraltar was usually between north and N.N.E., but was N.W. on one night when clouds obscured the stars.

4. Within the periods of east winds, observed migration was correlated with dry weather and rising night temperature in Morocco, but not merely with high temperature. It may also have been correlated with clear skies, but there is slight evidence that cloud cover also caused increased drift.

5. Migration of raptors and storks was seen on most days. Largest numbers were seen at the east end of the Straits in west winds, and vice versa; this is probably due to drift.

6. Other day‐migrants seen included Turtle Dove Streptopelia turtur, Bee‐eater Merops apiaster, Swift Apus apus, Alpine Swift A. melba, Swallow Hirundo rustica, Sand Martin Riparia riparia, and Short‐toed Lark Calandrella cinerea. Many were drifted west of the Straits, retaining their N.E. heading, but others–perhaps those breeding in western Iberia–were seen flying N.W. after crossing the Straits.

7. Large numbers of Black Terns Chlidonias niger were seen flying east or N.E. on a few days of strong east wind.
OBSERVATIONS ON THE BIRDS OF BULGARIA
Authors: Mountfort Guy , Ferguson‐Lees I. J.
Published: April 2008

The results of an expedition to Bulgaria during May and June 1960 are described. The majority of observations were made in the eastern regions of the Danube, the Dobrudja and particularly the lakes and woods of the Black Sea coast. Although, apart from the national scientific bodies, there is as yet little apparent interest in ornithology as such in Bulgaria, the laws protecting wild birds and the provision of sanctuaries are shown to be adequate. There is, however, evidence that the populations of certain larger birds such as pelicans, vultures and eagles have declined seriously, chiefly as a result of intensive agriculture, land reclamation, the annual cutting or burning of reed‐beds or the use of poison‐bait to control wolves. Other bird species are shown to have extended their ranges and some to have increased in numbers. Comparisons are made with the observations of earlier writers. Comments on observed migration are included in the Systematic List, which embraces 220 species, of which 205 were recorded in the course of the expedition.
THE DISPLAYS GIVEN BY PASSERINES IN COURTSHIP AND REPRODUCTIVE FIGHTING: A REVIEW
Authors: Andrew R. J.
Published: April 2008

The components of the displays of passerine courtship fall into at least seven major groups: those of sexual, aggressive, fear, alert, nesting, parental and begging responses. All may occur also during reproductive fighting. However, in order to present the observational data reviewed here it was necessary to classify display components on form alone. In each case distribution through the passerines, and possible origin and homologies, are discussed. The categories used were:–

Bill raising.This is characteristic of male courtship and reproductive fighting displays in many groups, but usually only occurs in one of the two contexts in any particular species. There is evidence that it may sometimes be homologous in both contexts.

Bill lowering.Most groups possess this component. Its most common origin is probably from lowering the bill to pick up or insert nest material.

Wing vibration.In some groups the wing vibration of male courtship appears to be homologous with that of the female precopulatory display, in others with that given when begging for food.

Feather raising.One of the main sources for the feather raisings of displays appears to be feather raisings normally given in response to thermal stimuli.

Components of the head‐forward posture.This posture and that of begging have nearly all their components in common. Possible homologies between them are discussed.

Lateral asymmetry.Lateral tilting of the body together with turning of the tail appear to be almost confined to the Carduelinae,Fringillaand the Estrildinae.

Components of the female precopulatory display.The passerines can be divided into two groups according to the presence or absence of vertical tail vibration in the female precopulatory display.

Song.Passerine song is best regarded as derived from contact calls. It still retains much of the same motivation and is similarly facilitated by androgens. The two extreme conditions (which are connected by all intermediates) within the passerines are those species in which the male sings only when alone and those in which there is so rigid an association between courtship displays (usually a bow) and song that males display even when singing alone.

Systematic implications of the distribution of these different components are discussed. It seems likely that the Estrildinae and Ploceinae form a natural group which may be related to the Corvid assemblage. A number of other relationships are suggested, but the data do not allow any firm conclusions.
THE TROPIC BIRDS (GENUSPHAETHON) OF ASCENSION ISLAND
Authors: Stonehouse Bernard
Published: April 2008

This paper is an account of investigations into the breeding cycles and breeding biology of two species of tropic bird, Phaethon ae. aethereus and Phaethon lepturus ascensionis, on Boatswain Bird Island, Ascension Island, in the southern Atlantic Ocean. Investigations covered the period November 1957–March 1959, and involved 700 marked nests and over 1,400 marked birds.

Both species were found to lay in every month of the year, although the number of eggs laid per month varied according to cyclical patterns peculiar to the two species. Individually, birds were found to breed at intervals of five to ten months (P. lepturus) or nine to twelve months (P. aethereus) according to the success or failure of their previous cycle; in either species those which were previously successful laid again towards the higher end of the range, those which were previously unsuccessful laid earlier, according to the length of time taken over incubating or rearing before loss. The interval between successive layings was determined in successful breeding by the length of the sexual cycle, i.e. the time taken by courtship, incubation, the rearing of the chick and the complete moult of body feathers, and was some 20% longer in P. aethereus than in the smaller P. lepturus. Unsuccessful breeders occasionally re‐laid soon after the loss of egg or chick, but were more likely to lose their nest‐site to usurpers, fail to lay again, and undergo a post‐nuptial moult similar to that of the successful breeders.

The overall pattern of breeding, i.e. the shape of the curve showing the number of eggs laid per month, was in either species determined by (a) the ratio of successful to unsuccessful breeders and (b) the length of the successful sexual cycle. Red‐billed Tropic Birds (P. aethereus) followed a pattern showing marked peaks and low points of activity, with peaks spaced eleven months apart. Yellow‐billed Tropic Birds showed a pattern in which successive peaks were spaced only nine months apart and laying was spread more evenly throughout the year. These differences are related to differences in the size of the two species, the larger P. aethereus taking longer to breed and being more successful in interspecific competition for nest‐sites.

Details of breeding behaviour, food, egg measurements, rates of growth of chicks, nest mortality and fledging success are given, with especial reference to P. lepturns which on Boatswain Bird Island outnumbered P. aethereus approximately in the ratio 2:1. A partial sexual dimorphism of colour in P. lepturus is also described.
THE MADEIRAN STORM PETRELOCEANODROMA CASTRO
Authors: Allan R. G.
Published: April 2008

The Medeiran Storm Petrel breeds annually on Boastwain Bird Island and probably has a 12‐month sexual cycle. The birds first arrive in July and most of the eggs are laid in November. During 1958–59 when the British Ornithologists' Union Centenary Expedition was on Ascension Island, the population of petrels was calculated to be 3,000 birds. There were signs of overcrowding in the colony, which reduced the breeding success. The behaviour of the colony suggested that there was a fertility gradient through the population. That this gradient might change in response to population fluctuation is discussed.

A detailed description is given of the growth and development of normal and retarded chicks together with recordes of egg losses and injuries to adults and chicks.
L. TINBERGEN'S HYPOTHESIS OF THE ROLE OF SPECIFIC SEARCH IMAGES
Authors: Gibb John A.
Published: April 2008

The paper opens with an appreciation of L. Tinbergen's findings, that predation by tits on certain caterpillars in summer is less than expected on the basis of chance encounters at very low and very high caterpillar densities, but more than expected at moderate densities; and of Tinbergen's hypothesis that birds only find and accept prey after acquiring the appropriate specific search image, which only happens when the prey exceed a certain threshold density.

Larvae of the eucosmid Ernarmonia conicolana (Heyl.) spend the winter concealed just beneath the cuticle of ripening pine cones, where they are preyed upon by tits which leave recognisable traces of their attacks on the cones. Their predation was exceptionally light at very low densities, but increased abruptly with slightly increased densities of conicolana. Contrary to Tinbergen's hypothesis, the birds probably found and sampled the larvae at the very low densities, but rejected them as an uneconomical food.

The tits' predation intensified with increasing density of conicolana; but relaxed somewhat at higher, less frequently occurring, densities. This implies that the birds learn how many larvae to expect in different localities; and slacken their search when the expected number of larvae have been taken from the cones.

Some implications of this predation by expectation are discussed. It probably cannot account for the reduced predation on caterpillars at high densities recorded by Tinbergen; but could apply to a wide range of concealed foods at which birds (or other predators) leave recognisable traces of their attacks.
EARLY BREEDING IN TENERIFE
Authors: Ennion E. A. R. , Ennion D.
Published: April 2008

The birds in an area of about half a square mile of mixed terrain, ranging from sea level to 2,500 ft. at Bajamar on the N.E. coast of Tenerife, were studied from 2 January to 25 February 1961. The populations, breeding and ecology of the resident species were investigated, especially of the warblers (Chiffchaff, Sardinian and Spectacled Warblers and Blackcap), but including also Kestrel, Hoopoe, Berthelot's Pipit, Blackbird and some species of finches.

“Early” breeding starting in the second half of January is shown probably to be regular, and dependent on the insects which result from a flush of vegetation, itself resulting from winter snow and rain. This period is usually followed by drought, and “normal” breeding follows fresh rain and renewed plant growth in March.

The significance of these findings, previously not even suspected, is discussed.
THE DEVELOPMENT OF SONG IN THE BLACKBIRD TURDUS MERULA
Authors: Hall‐Craggs Joan
Published: April 2008

An analysis is made of the song of one wild Blackbird in 1957 in south Oxfordshire. An arbitrary classification of the song phrases is suggested.

Sample recordings were made throughout the song period, and methods of analysis are described.

The composition of the song at the beginning of the season is described. Reference is made to the “practising” habit, to the early formation of compound phrases and to a tendency to use certain phrases in particular contexts.

26 phrases, used at the outset of the season, constituted a basis upon which the developed forms were built. Five means of treating existing phrases were found: (1) whole phrases and extracts from phrases were combined to form new phrases; (2) new material was added to existing phrases; (3) notes contained within the phrase were repeated; (4) new terminal decorations were added to phrases; (5) phrase contraction by the omission of notes occurred.

Phrases were organized into recurring series, many of which became permanent. Such organization of the song phrases, and the creation and extension of compound phrases, continued throughout the season. The influence of terminal decorations upon phrase order is noted. There was little evidence of disintegration of the song as the season ended.

It was found that an increase in frequency of occurrence of developed forms was usually balanced by a corresponding decrease in the use of the phrases from which they were derived. Certain highly developed forms were used much more frequently than their related basic phrases. Infrequently used developed forms appeared to be of transitional character, while those that were not retained were replaced by new forms.

The response to the song of another Blackbird is described. Counter singing, communal singing and antiphonal singing by the two birds were recorded. The scolding “churr” of a Blue Tit was copied and retained as a terminal decoration to a phrase.

The mature song presented a distinct contrast to the early song. Manipulation of material rather than material as such was responsible for the song development. It is suggested that deliberate selection of material occurred.

The song is discussed as a functional and an aesthetic activity and an attempt is made to correlate the two aspects.
LIFE HISTORY OF THE WHITE‐TAILED TROGON TROGON VIRIDIS
Authors: Skutch Alexander F.
Published: April 2008

In southern Costa Rica the White‐tailed Trogon inhabits the upper levels of heavy forest, from sea level up to about 3,500 feet. It is found alone or in pairs, never in flocks. It subsists on insects and fruits plucked while hovering on wing, and occasionally it catches a lizard on the ground. Its song, an accelerated series of soft, melodious notes, serves to distinguish it from associated trogons.

The preparation of nests begins in the dry month of March, the male taking the initiative. The cavity is carved in the soft wood of a decaying trunk, in or near the forest, by both sexes working alternately. An ascending shaft leads into the top of an ellipsoidal chamber placed deep in the wood. In other regions similar chambers are carved in termitaries.

Laying occurs from mid‐April to August. Two or three white eggs are deposited, at intervals of two days, on wood particles which cover the floor of the unlined nest.

The eggs are incubated almost constantly by both parents, sitting alternately. Each day the male takes one long session lasting six to eight hours, and the female sits the rest of the time, including the night. At one nest, the male sat through the middle half of the day. At another nest, he often began to incubate before sunrise, and the female returned to relieve him soon after noon. The incubation period is 16 or 17 days. Eggs which failed to hatch were attended for 51 days, until they disappeared.

The nestlings are hatched with naked, pink skin. Both parents feed them infrequently but with very substantial portions. Two unfeathered nestlings were fed only two to four times in the first six hours of the day. A single older nestling received only nine meals in 11 hours. In the first days after hatching, the nestlings are brooded a little by both parents, but daytime brooding ceases long before they are feathered. One female covered her nestlings by night until they were 11 days old. At one nest, the female vanished soon after the eggs hatched, and the male alone then reared the nestling.

There is no nest sanitation.

Although feathered at the age of about two weeks, a nestling remained in the nest until it was 25 days old.
A RE‐EVALUATION AND REDESCRIPTION OF A DIFFICULT ASIA MINOR PHYLLOSCOPUS
Authors: Watson George E.
Published: April 2008

Phylloscopus brevirostris (Strickland) of Asia Minor is redescribed. It appears to be closest to lorenzii of the Caucasus on the basis of structure and pattern, but approaches P. collybita abietinus, which also breeds in the Caucasus, in pigmentation. Two species of chiffchaff type are recognized, P. collybita, a migratory northern and western form, and a sedentary south and eastern form (probably derived from a northern population of P. collybita which had reduced lipochromes) for which P. brevirostris may be the appropriate name.
THE BREEDING BIOLOGY OF THE LITTLE SPARROWHAWK ACCIPITER MINULLUS
Authors: Liversidge R.
Published: April 2008

A pair of Little Sparrowhawks was under close study throughout one breeding period. The habitat, territory, territorial behaviour, courtship, and nest building are described. The share in incubation (31–32 days) by both sexes and brooding of the chick is illustrated. Four developmental stages of the young nestling are given (nestling period 25–26 days). Food, feeding and food requirements are estimated, and the call notes described.
MIGRATION IN THE OUTER HEBRIDES STUDIED BY RADAR
Authors: Lee S. L. B.
Published: April 2008

The main passerine arrivals and departures in the Outer Hebrides in autumn are (i) S.E. from Iceland, presumably of Wheatears and Meadow Pipits in September and of Redwings in October; (ii) E.S.E. from Greenland, mainly of Wheatears; (iii) slightly west of south from the Faeroes; and (iv) with drift by easterly winds, of thrushes and drift‐migrants between west and south from Norway, (v) One W. movement was also recorded.

Arriving migrants flew too low over the sea the sea during the second part of the night to be detected by radar, but rapidly gained height at dawn, at which time drifted Continental migrants re‐oriented S.S.W. and S.S.E. (from W.S.W.), but Icelandic and Greenland birds evidently did not change direction.

In autumn, the presumed Wheatears, Meadow Pipits and Redwings were far less deterred from setting out by moderate head‐wings or strong cross‐winds than similar birds in Norfolk. But in spring nearly all the sizeable movements occurred with following or light winds.

There were three main times of departure from Lewis in autumn, at nightfall (presumed night‐migrants), some two hours before sunrise (presumed night‐migrants again) and around sunrise (diurnal migrants).

The presumed Icelandic Wheatears and Meadow Pipits, and until mid‐October the presumed Redwings, departed on the same S.E. heading as that on which they arrived. But after mid‐October the Redwings left almost due south, perhaps a re‐determined heading. On one night in late October about one‐fifth of the presumed southward departure went northwest, apparently because the birds mistook the rising moon for the set sun. Presumed Greenland Wheatears left on the same heading as that on which they arrived, but Continental thrushes, which must have arrived W.S.W., left S.S.W. on subsequent nights.

The movements of non‐passerine birds are briefly discussed.

In spring, the incomplete observations refer primarily to N.W. departures of Redwings, waders and geese, with some departures N.N.E., presumably for the Faeroes, others E., probably of Blackbirds, and yet others S.E., probably reversed movements.
ASPECTS OF THE BEHAVIOUR OF THE MAGPIE GOOSE ANSERANAS SEMIPALMATA
Authors: Davies S. J. J. F.
Published: April 2008

Part 1.

Some action patterns of the Magpie Goose are clearly ritualized as signal actions, whilst others, although not so ritualized, are none the less characteristic of particular moods of the bird. It is considered that the action patterns form a simple language such that individual geese are aware and can often anticipate the actions of other geese.

Particular attention is given to fighting actions, which appear on the second day of a goose's life, and to “concerting”, at first a threat display but later also used in pair maintenance, where it appears very similar in function to the triumph display of true geese.

Part 2.

The family, comprising the reproductive group and its offspring, is the fundamental entity in Magpie Goose flocks. Males may be paired to one or two females, but they dominate their mates and offspring and defend a “territory” around them from other geese.

Magpie Goose flocks are built up of families, each of which acts independently except in an alarm situation, when the flock acts as an entity. Flocks build up at feeding, roosting and watering sites, and although constant in location are probably composed of a different combination of families each day. The flock behaviour of Magpie Geese closely parallels that of the true geese.

No alarm stimuli have been found which are innately recognized by Magpie Geese. The fact that alarm stimuli are learnt, taken with the unstable nature of the flocks, suggests that it may be very difficult to produce a “magic wand” which effectively scares the birds from rice crops.
THE EXPERIMENTAL DEMONSTRATION OF PRE‐MIGRATION ACTIVITY IN THE ABSENCE OF FAT DEPOSITION IN BIRDS
Authors: Lofts B. , Marshall A. J. , Wolfson Albert
Published: April 2008

Under dietary conditions that experimentally prevented the accumulation of “pre‐migratory” depot fat, typical nocturnal migratory restlessness developed in the Brambling Fringilla montifringilla. Subsidiary data are presented from Junco hyemalis and Zonotrichia albicollis.

In captive controls, the rapid accumulation and subsequent utilization of body fat closely paralleled the onset and waning of nocturnal unrest.

Although the Brambling accumulates fat reserves before both nuptial and contra‐nuptial flights, it would seem that the presence of such is not an essential element of the so‐called “total physiological state” necessary for the onset of migration.
NOTES ON BIRDS IN THE GAMBIA
Authors: Cawkell E. M. , Moreau R. E.
Published: April 2008

Recent observations in The Gambia have shown that the status of many species has changed in the last forty or fifty years and have provided data on the local breeding seasons for a number of birds. Several species have been found for the first time in this part of West Africa. The various birds concerned are given in a systematic list, together with notes on all the Palaearctic migrants so far recorded from The Gambia. Organized research is recommended on several lines: on the sequence of food sources, especially through the long and severe dry season, when Palaearctic birds are added to resident and when some African species breed. The bird ecology of the mangroves remains to be worked out, and also the relative importance to birds of cleared ground and untouched “bush” at all seasons.
“NONSENSE” ORIENTATION AS A POPULATION VARIANT
Authors: Matthews G. V. T.
Published: April 2008

Using 2,570 Mallard, the “nonsense” orientations of two largely separate stocks are compared. Slimbridge birds head off predominately northwestwards throughout the season. Birds caught at Peakirk showed a similar orientation during the early autumn, but during the winter scattered virtually at random, yet without behaving as if disorientated.

A sample of 188 Mallard from London orientated in southerly directions both in autumn and spring, yet could not be responsible for the change at Peakirk because they would not disperse so far. 180 young Mallard from Slimbridge and London stocks were reared in large aviaries. Their first flights were too abbreviated for conclusive results but differences between the stocks were indicated and it is possible that “nonsense” orientations are not learned responses to the local topography.

Ringing recoveries show that the timing of the arrival of immigrants from the Continent coincides with changes in orientation at Peakirk and that their distribution is such that it could explain the different results at Slimbridge. Preliminary releases of Swedish‐caught Mallard strongly support the argument.

The implications for the study of bird navigation are briefly discussed.
PRELIMINARY RESULTS FROM NEW METHODS OF INVESTIGATING THE PHYSIOLOGY OF BIRDS DURING FLIGHT
Authors: Eliassen E.
Published: April 2008

The physiology of birds in flight is discussed in relation to (a) energy metabolism; (b) heat regulation, including the importance of the ventral part of the wing and its temperature, measured in a bird gliding in a specially constructed wind tunnel; and (c) cardio‐vascular responses, measured in flying birds by telemetric methods.
THE FOOD AND FEEDING HABITS OF GOLDENEYE BUCEPHALA CLANGULA IN GREAT BRITAIN
Authors: Olney P. J. S. , Mills D. H.
Published: April 2008

The food and feeding habits of Goldeneye Bucephala clangula are described, based on the analyses of 51 stomach contents and a brief review of the literature. The type of food taken depends on the type of habitat being used, the availability and size of the food items and on the methods of feeding—though animal material largely predominates.

In estuarine and coastal areas, small crustaceans and in particular Carcinus maenas figured highly in the diet, with some molluscs and small fish. In two brackish‐water feeding birds, seeds formed the bulk of the food, some caddis‐fly larvae also being taken. In freshwater feeding birds insects predominated, particularly Trichoptera larvae, chironomid larvae and the adults of Corixa spp. Some crustaceans (Asellus, Gammarus) and small molluscs were taken and occasionally small fish. A small amount of plant material was taken in the form of seeds, mainly Potamogeton spp.

The relation between Goldeneye and fishing interests is briefly discussed and it is concluded that fish normally form a small part of the diet and it is unlikely that any serious depredation of fish stocks is common.