bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE EFFECT OF EGG WEIGHT ON THE SUBSEQUENT GROWTH OF NESTLING GREAT TITS PARUS MAJOR
Authors: Schifferli L. 
Published: April 2008

SummaryEggs of known fresh weight were removed from Great Tit nests shortly before hatching and artificially incubated. Four to eight chicks were returned to each nest‐box on their hatching day and reared by foster parents. The effect of egg weight on subsequent growth was studied for 81 nestlings (13 broods), 50 of them (8 broods) up to the 17th day.Hatching success of 275 eggs in the incubator was 67·6% and was not correlated with egg weight.Egg weight had a significant effect on nestling weight up to the 14th day. Young hatched from lighter eggs grew more slowly at the beginning, but recovered before fledging. Mortality after fledging seemed not to be influenced by egg weight.Maximum weight (mean 19 g) was attained between the 12th and the 17th day and was positively correlated with egg weight.The effect of brood‐size (small in the experiments) on growth increased significantly with age. The range of egg weight for a nest had a significant effect on growth at the beginning, but a small and not significant effect after the 10th day.The growth of each brood on any particular day was expressed as a deviation from mean growth. These growth deviations, plotted against date, were similar in all nests and were not correlated with any weather data.The fledging success of 260 early broods was independent of egg weight, but it was positively correlated with egg weight in 78 late broods (data from 1965–71).The ecological importance of egg weight at different times of the breeding season is discussed.
RAPTOR MIGRATION ACROSS THE STRAITS OF GIBRALTAR
Authors: Evans P. R. , Lathbury G. W. 
Published: April 2008

SummaryThe visible migration of birds of prey at Gibraltar is analysed from records kept throughout the spring passages of 1967–70 and the autumn passages of 1967–69. In early spring most visible passage is noted in the afternoons, whereas radar observations by Houghton (1970) indicate passage in the mornings. Later in the year an additional burst of visible passage sometimes occurs in the early morning, but it is concluded that most morning movements take place above visible range. Visible migration is recorded on most days of westerly wind during the migration seasons at Gibraltar. Passage is rarely seen when the winds are easterly. It is argued that under the latter conditions a strong upcurrent of air (standing wave) is formed over Gibraltar, and that this carries nearly all migrants above visible range.Observations of visible passage elsewhere in the Straits suggest that, in spring, raptors of all species cross on a broad front from Tangier to Ceuta, except Honey Buzzards, which probably cross chiefly near Ceuta. In autumn, all species from northern Europe cross chiefly between Tarifa and to the east of Gibraltar, while birds from western Iberia probably cross mainly near Tarifa.The periods of passage of the common migrant species are summarised.On the basis of visual observations and published radar results, it is argued that raptors can compensate for lateral drift by the wind and so fly on chosen courses; but that in very strong cross‐winds, e.g. the easterly Levanters, they may have to let themselves be drifted off‐course.
POLYMORPHISM IN THE ARCTIC SKUA STERCORARIUS PARASITICUS IN ICELAND
Authors: Bengtson Sven‐Axel , Owen D. F. 
Published: April 2008

Summary.A survey of the frequency of the dark and light colour forms of the Arctic Skuas breeding in Iceland provided evidence of a south‐north cline, the light form being more frequent in the north than in the south. In one area there were significantly more dark birds in 1971 than 30 years earlier, but in two other areas there was no evidence of a change in frequency. In northeast Iceland, where the light form is common, there was a statistical tendency towards unlike matings. It is suggested that the adaptive significance of the forms is to be sought in terms of facilitating departures from random mating, the genetic consequences of which are understood in general terms, although the ecological significance remains obscure.
A REANALYSIS OF NEST STRUCTURE IN THE WEAVERS (PLOCEINAE) USING NUMERICAL TAXONOMIC TECHNIQUES
Authors: Schnell Gary D. 
Published: April 2008

Summary.Variables of nest architecture and construction behaviour of 62 species of ploceine finches studied by Crook (1963) were reanalysed using multivariate statistical techniques. Phenetic assessments were based on 38 two‐state characters for 48 OTUs. Product moment correlation coefficients and average distance coefficients were used as measures of similarity, and species were clustered using the unweighted pair‐group method with arithmetic averages. A three‐dimensional model was constructed of species plotted with respect to the first three principal components extracted from a matrix of correlations among characters. Principal component and factor analytic techniques were employed to determine trends in character variation.The phenetic affinities expressed in the 3‐D model and two phenograms show many similarities to the phenetic groupings deduced by Crook. However, there were also some differences in interpretation. Crook's Modes C and D were shown as distinct clusters in my analyses, but Modes A and B did not separate completely. In particular, the globular nest of P. baglafecht of Mode A, Type IV, grouped with kidney‐shaped nests of species of Mode B, Type Va. The treatment of P. pelzelni, P. madagascariensis, and P. philippinus in my analysis differed somewhat from Crook's. The resulting cluster of F. sechellarum and M. malimbicus brought out some effects of standardising data on resulting interpretations of similarity.Species within the subtypes of Crook usually remained close together, but the affinities between subtypes (and types) often differed between our studies. The results of factor and principal component analyses indicate that the main trends in character variation concern those traits found together in (a) M. rubriceps; (b) A. unicolor and Pa. superciliosus; (c) forest birds; and (d) non‐forest birds. These groups also are the main clusters. Differences in Crook's and my results are discussed and some of the advantages of utilising numerical techniques to describe similarity are mentioned.
SOCIAL BEHAVIOUR OF BREEDING WESTERN SANDPIPERS CALIDRIS MAURI
Authors: Holmes Richard T. 
Published: April 2008

Summary.The behavioural interactions among breeding Western Sandpipers (Calidris mauri) are described, and interpreted in terms of their adaptive characteristics.Upon arrival in early spring, males disperse onto territories through mutual antagonism. Territorial advertisement and maintenance is accomplished through display flights low over the ground, which are accompanied by soft buzzy vocalisations. These characteristics of display are related to the fact that this species occurs in dense, localised breeding populations, where longdistance communication is unnecessary.Because densities are high and feeding often occurs in communal areas off territory, violations of territorial boundaries are frequent. The result is an extremely high intensity of interactions among individuals. Chasing and physical combat between males is frequent and generally un‐stereotyped. Birds nesting on territories away from the feeding sites often fly high above the other territories, and in doing so avoid being chased.Western Sandpipers form monogamous pair‐bonds which are maintained until the young are ready to fly. The initial association of the pair is facilitated by a strong tendency to return to the previous site and by the advertisement of the males in which a specific vocalisation is given. Once the female is present on a male's territory, she is courted persistently by him and gradually begins to participate in his scraping displays. Pair‐bonds are re‐enforced by the close association of the pair during the pre‐nesting period and through a simultaneous preening display.An hypothesis is developed that the participation of both sexes in incubation serves primarily as a means of pair‐bond maintenance, acting to keep both parents present until after the young hatch. At this time, their presence is needed to provide protection for the precocial young against predators.
NEST‐BUILDING BEHAVIOUR OF QUAKER PARROTS MYIOPSITTA MONACHUS
Authors: Harrison C. J. O. 
Published: April 2008

Summary.An account is given of nest‐building by captive Quaker Parrots Myiopsitta monachus. Nests were made by thatching movements, twigs being inserted into a base by a sideways movement of the head. A downward slanting sheaf was formed around an internal cavity. The lip of the nest‐hollow was formed by pulling up and inserting the ends of some twigs. The cavity was shaped by chewing off projecting ends, and floored with chewed and shredded twigs.
PATTERNS OF GROWTH IN BIRDS. II. GROWTH RATE AND MODE OF DEVELOPMENT
Authors: Ricklefs R. E. 
Published: April 2008

Summary.This analysis was initiated to examine the relationship between the rate of growth in birds and their development of mature function. The literature was surveyed for data on growth and development, and the growth curves of 81 species were chosen for the analysis. Growth curves of most species were fitted with the Gompertz equation, and the rate constants of the equation were used as an index of the growth rate. For those species whose curves were fitted better by other equations, with a slightly different form, appropriate conversion factors, derived in this paper, were employed.Among species with similar modes of development, growth rate decreases with increasing body weight in an allometric manner, with slopes of –0.26 to –0.42, depending on the group. Between groups, the rate of growth in body weight was found to be closely associated with the rate of development of function, in particular, the acquisition of flight. Among those species that can walk at an early age, but acquire flight relatively late, the rate of growth depends primarily on the relative size of the musculature of the lower extremities.Data are presented to refute the hypotheses that growth rate is adjusted to nestling mortality, or that the energy requirements of the young (and hence their growth rates) are balanced against brood size. It is concluded that most species grow at some physiologically maximum rate, but as yet it is not possible to distinguish between limitation of growth rate at the level of the organism or at the level of the tissue.
LEK BEHAVIOUR AND BREEDING OF GUY'S HERMIT HUMMINGBIRD PHAETHORNIS GUY
Authors: Snow Barbara K. 
Published: April 2008

SummaryGuy's Hermit Phaethornis guy, a large forest hummingbird, was studied for 21/2 years in the Northern Range of Trinidad. Regular observations made at a lek of 16 males showed that leks are occupied from November until the beginning of July, and that individual birds retain their lek territories from year to year and use the same perches.The usual song is a monosyllabic note regularly repeated, but the quality of the note varied between different leks and between different parts of a lek, and a few males had a disyllabic song. Young males join the lek between April and June and learn the song of their immediate neighbours. Their plumage, when they first join, is similar to a female's, with distinct pale super‐ and subciliary stripes. The acquisition of the dark head of the adult male probably takes four years.Before they land on their lek perches, males perform an elaborate aerial display in which the red gape is flashed open and a loud tock is uttered. When males visit each other they rapidly change places on the lek perch, the airborne bird performing the tock‐display over the perched bird. A similar tock‐displaying with changing of place occurs when females visit males; twice these were seen to culminate in mounting. Periodically all males at the lek ‘false‐mate’ with a leaf or other piece of vegetation near their lek perches, after tock‐displaying above it. Young males false‐mate much more frequently than older males.The breeding season lasts for eight months, the peak of breeding coinciding closely with the period when the two most important sources of nectar (Heliconia bihai and Pachystachys coccinea) are available. Males occasionally visit nests, and possibly assist in defending them. Undefended nests are quickly dismantled by other birds in search of nest‐material. Of 19 nests found before the clutch was complete, five (26%) were successful. The incubation period is 17–18 days, and the fledging period 21–23 days.
NOTES ON GEOGRAPHICAL VARIATION AND THE ANNUAL CYCLE IN PATAGONIAN POPULATIONS OF THE RUFOUS‐COLLARED SPARROW ZONOTRICHIA CAPENSIS
Authors: King James R. 
Published: April 2008

Summary Zonotrichia capensis australis inhabits Argentina from the northernmost limits of the Patagonian steppe south through Tierra del Fuego, and extends westward to the Pacific slope in southern Chile. At least part of the population has a north‐south migration along the Andean foothills of Argentina as far north as southwestern Bolivia. The breeding range of australis is bounded on the north and northwest by subspecies of Z. capensis (chilensis, choraules, and possibly hypoleuca) having conspicuous black lateral crown‐stripes. Topotypical australis (Tierra del Fuego) have plain grey crowns, but the frequency of black nuchal markings and faint lateral crown‐lines increases northward in the coastal populations. In inland populations (Andean piedmont) the frequency of black crown markings is apparently reversed, increasing southward. The size (wing‐length, tarsus, bill, and probably body‐weight) of australis decreases northward in both coastal and inland samples.The nesting season of australis begins in late November and early December and extends to mid January and early February. Postnuptial moult begins from mid December to early January. Moult proceeds while the testes are apparently still functional. Postnuptial moult terminates from late January through mid March. There is no evidence in the current data of geographical trends in the chronology of nesting and postnuptial moult. The calendars appear to be about the same throughout the range of australis.Postjuvenal moult begins about 4–5 weeks later than the onset of postnuptial moult and terminates in the latest birds in about mid March. Northward migration begins at about this time.
BREEDING NUMBERS AND REPRODUCTIVE RATE OF EIDERS AT THE SANDS OF FORVIE NATIONAL NATURE RESERVE, SCOTLAND
Authors: Milne H. 
Published: April 2008

SummaryThe total population of Eiders at the Sands of Forvie National Nature Reserve, Aberdeenshire, increased from about 3000 birds during 1961–63 to about 4800 birds in 1964–70. At the same time the estimated number of breeding pairs increased from about 1200 in 1961–63, to about 1800 in 1965–68 and to 2000 in 1970.The mean size of completed clutches was 4.4; the number of eggs in a clutch showed a significant decline during the season from an average of 4.7 to 3.4 in most years. The overall hatching success was 63%, but there was a decline with season as a result of increased losses to predators.In 1964 and 1969 laying was retarded, mean clutch‐size reduced, and the number of birds attempting to lay dropped by half, due to inclement weather just at the onset of laying. In 1969 the eggs produced were smaller than in other years, and hatching success was lower.The female incubates without feeding, and is required to store sufficient energy, in the form of fat, to last her through the 26 days in addition to producing her clutch of eggs. An hypothesis is advanced which relates the feeding efficiency of the paired female immediately prior to laying to her egg production and incubating pattern, and which offers an explanation of the decline in clutch‐size and hatching success evident during the season.In most years less than 5% of hatchlings survived to fledge; high survival was recorded in 1963, 1968 and 1970. Following the high production in 1963 the population increased in 1964 and the breeding stock in 1965 (females start to breed at two years old). The corresponding changes, following good breeding in 1968, were not so clearly detected because of unusually high adult mortality from oil pollution at the winter grounds in 1968 and the ‘late’ breeding year in 1969. The breeding stock in 1970, however, was higher than in any other year. This population continues to grow apparently as a result of its own reproductive output checked only by low productivity in most years and occasional high adult mortality.
SPRING MIGRATION OF EIDERS SOMATERZA MOLLISSIMA IN SOUTHERN SCANDINAVIA
Authors: Alerstam Thomas , Bauer Carl‐Axel , Roos Gunnar 
Published: April 2008

SummaryEider migration in southern Scandinavia in spring 1972 was studied simultaneously at three radar stations and ten field observation sites. The Eiders winter in Danish and West German waters, from which they set out on spring migration on courses ranging from SE to NE; those from the northern part of the wintering area flew SE, those from the south NE, while birds wintering in between these geographical extremes set out on intermediate courses around E.Radar showed that most Eiders fly over the island of Zealand and the peninsula of Skåne, but only exceptionally further north over Sweden. Few Eiders crossing land were registered by field observers and most evidently passed at high altitudes beyond the range of vision. After having crossed Skåne, on varying tracks both south and north of east, the Eiders descended and changed flight direction towards NE.Some Eiders from the northern part of the wintering area circumnavigated Skåne, passing south along the Swedish coast of the Sound, crossing the very narrow peninsula of Falsterbo, and subsequently following the south coast of Skåne eastwards. Eiders from southern Denmark and Germany were often deflected eastwards along the south coast.After having passed Skåne no significant land crossings were made. Upon reaching the province of Blekinge on a course towards NE, the Eiders were deflected E to ESE along the coast and later NNE along the west coast of Öland through Kalmar sound.Approximately 350 000 ducks migrated during daytime of the study period, 250 000 crossing the land of Skåne while 100 000 passed along the south coast. Almost 300 000 migrated north in Kalmar sound, and 17 % of all Eiders passed east of Gland over the open sea.Three distinct peaks of activity during the day were noted in Skåne. The first, at around sunrise, originated from birds resting in waters off Skåne. The second occurred about four hours later and probably consisted of birds which had departed from the wintering area in the early morning. A final peak at sunset was often recorded. Migration also took place during the night, but involved only one fifth of the total number.From combined radar and field counts the total Baltic Eider population is estimated to have been 700 000–800 000 in spring 1972, indicating about 300 000 breeding pairs in the Baltic Sea.
THE VISIBLE MIGRATION OF RAPTORS OVER THE MALTESE ISLANDS
Authors: Beaman Mark , Galea Charles , Beaman Mark 
Published: April 2008

SUMMARYWhilst the large migrations of raptors at the Bosphorus and at the Straits of Gibraltar have been documented in some detail, the movements which take place across the Mediterranean itself have been neglected. This paper reports observations of the visible migration of raptors over the Maltese Islands during 1969–73.The largest numbers of raptors were recorded both in spring and autumn during contrary winds or overcast conditions. Normally very few were seen before the early afternoon at either season, in spite of the much shorter minimum sea‐crossing in autumn. Large passages occurred in winds with easterly or westerly components. It is therefore concluded that eastward drift does not greatly affect the numbers seen in Malta, as had been suggested by De Lucca (1969); rather that most influxes occurred in the late afternoon during unfavourable meteorological conditions. At other times most migration was probably above the visible range.The number of raptors observed on passage in the Maltese Islands was small compared with movements at the Bosphorus or at Gibraltar. Nevertheless, the numbers of the narrow‐winged species (i.e., Ospreys, harriers and falcons) compare favourably with records at the narrow crossings. The only large soaring species commonly seen in Malta was the Honey Buzzard. Evidence is presented which suggests that the volume of Honey Buzzard migration across the central Mediterranean may be much larger than was formerly realized.
VOCALIZATIONS, SOCIAL ORGANIZATION AND BREEDING BIOLOGY OF THE TWITE ACANTHUS FLAVIROSTRIS
Authors: Marler P. , Mundinger P. C. 
Published: April 2008

SummaryA seven‐week study of breeding Twites at the mouth of the Trondheim fjord revealed that they are double brooded. The second clutch is started while the first nestlings are still dependent on both parents. Males defend a moving area around the female which becomes focused on the nest during incubation. Adult vocalizations recorded and analysed fall into seven basic categories. We believe this represents the entire repertoire, which is rather small, and may correlate with the visually open habitat. Nine measures of the tup‐up‐up flight call reveal that calls of a male and female that are paired match closely and differ from those of other birds in the area. This is taken as evidence that the Twite flight call is modifiable by learning, as in some other cardueline finches.
SYSTEMATICS OF PARROTS
Authors: Smith G. A. 
Published: April 2008

SummaryParrots comprise such an homogenous and natural order of birds that it has proved difficult to find substantial characters with which to subdivide them further.The classification, based largely on external morphology, which Salvadori proposed in 1891 has been the main source for almost all subsequent arrangements, which however, are inconsistent in the number of divisions and in the genera composing the divisions. The present paper is an attempt to reconcile the different arrangements by demonstrating instances of convergence and suggesting several additional features which may have use as systematic indicators.The following anatomical, morphological and ethological characters are considered: tongue, hyoid bone, bill, intestine, gall‐bladder, carotid artery arrangements, neonate chick, furcula, skull rump feathers, exposed epidermis, irides, erectile feathers, sexual dimorphism, colour of immature males, copulatory patterns, epigamic and agonistic display, nesting, foliage‐bathing, rain‐bathing, bathing, sunning and head‐scratching; the evidence of hybridization is also discussed. Convergence is demonstrated in ground feeding forms for skull structure, loss of furcula and an indirect head‐scratching behaviour.The following divisions are proposed: Platycercinae (Platycercini, Cacatuini, Nestorini, Strigopini); Loriinae (Loriini, Psittrichasini, Psittaculini, Micropsittini, Psittaculirostrini); Arinae (Arini); Psittacinae (Psittacini). Although this arrangement is very different in its larger groupings from any previous system, it very closely agrees with that of Salvadori in the number and in the constituent genera of the smaller groups.