bluuebunny/crossref_metadata_2025 huggingface dataset:
Rapid moult among palaearctic passerines in West Africa‐ an adaptation to the oncoming dry season?
Authors: BENSCH STAFFAN , HASSELQUIST DENNIS , HEDENSTROM ANDERS , OTTOSSON ULF
Published: April 2008

Moult of some palaearctic migrant passerines was studied at a wintering site in northern Ghana, West Africa. We present data on moult pattern and estimated moult duration for a sample of species. Savi's Warbler Locustella luscinioides, Woodchat Shrike Lanius senator and probably Grasshopper Warbler Locustella naevia deviated from the ordinary descendent moult sequence. Different measures of moult speed (moult speed of retrapped individuals, growth of individual feathers, wing raggedness and first date of completion of moult) showed unexpectedly rapid moult among individuals of several species, notably the Great Reed Warbler Acrocephalus arundinaceus and the Sedge Warbler A. schoenobaenus. The rapid moult might be an adaptation to a limited period of abundant food which comes to an end at the beginning of the dry season.
Optimal fat loads and long‐distance flights by migrating Knots Calidris canutus, Sanderlings C. alba and Turnstones Arenaria interpres
Authors: GUDMUNDSSON GUDMUNDUR A. , LINDSTRÖM ÅKE , ALERSTAM THOMAS
Published: April 2008

Arctic waders often build up large fat loads and complete their migratory journeys by a few long‐distance flights between traditional staging sites. Optimal fat loads and choices of staging sites differ depending on whether the birds are adapted to minimize energy or time spent on migration. In the latter case, we predict that the birds will depart for the next staging site when the instantaneous speed of migration expected after arrival at the next site, exceeds the corresponding speed at the departure site. The instantaneous migration speed is a function of the rate of fat deposition and the current fat load. As a consequence of this, overloading (birds deposit larger fat loads than needed merely for covering the flight distance to the next destination) and by‐passing of possible, but low‐quality staging sites, are expected under specific conditions in time‐selected migration.

Estimates of fat deposition rates and departure fat loads were obtained by captures of Knots Calidris canutus, Sanderlings C. alba and Turnstones Arenaria interpres in W. Iceland during spring migration. Further fat deposition data referring to spring migration of these species were compiled from the literature. Fat deposition rates at different sites, as measured by the daily gain in mass relative to lean body‐mass, range between 1.0 and 3.6%/day, and departure fuel loads (in % of lean body‐mass) between 27 and 73%.

Comparison with flight range estimates suggests that overloading may be a regular phenomenon during spring migration of Knots, Sanderlings and Turnstones. Furthermore, fat deposition rates at different staging sites, and the general difference in migration patterns between spring and autumn, indicate that by‐passing of possible staging sites may well occur. Hence, it cannot be excluded that the waders' migratory habits primarily serve to maximize the overall speed of migration.
Breeding density of Dippers Cinclus cinclus‘ Grey Wagtails Motacilla cinerea and Common Sandpipers Actitis hypoleucos in relation to the acidity of streams in south‐west Scotland
Authors: VICKERY JULIET
Published: April 2008

The distribution of breeding pairs of Dippers Cinclus cinclus, Grey Wagtails Motacilla cinerea and Common Sandpipers Actitis hypoleucos was assessed along 18 streams in south‐west Scotland during summer 1987, and the lengths of territories, occupied by 5 5 breeding pairs of Dippers, were measured. In each stream the water chemistry, physical structure (e.g. gradient, altitude, nature of bankside vegetation) and density of aquatic invertebrates was determined. The density of breeding pairs of dippers was significantly lower along streams of low pH (high acidity) and steep gradients, and territories were significantly longer at these sites compared with those of higher pH. Many of the invertebrate families that are important prey for Dippers were scarce at sites of low pH, particularly caddisfly larvae (Trichoptera) and mayfly nymphs (Ephemeroptera). The low numbers and large territories of breeding pairs of Dippers on acidic streams may be due to reduced density and diversity of macroinvertebrate prey. Stream pH was not an important correlate of the distribution or density of Grey Wagtails or Common Sandpipers. It is suggested that the lack of any similar effect of pH on these other two species compared with Dippers is attributable to differences in their feeding ecology.
Muscle protein loss in laying House Sparrows Passer domesticus
Authors: JONES MARILYN M.
Published: April 2008

In a study of female House Sparrows Passer domesticus, it was established that almost all of the lean dry material lost from the flight muscles during the period of egg formation and laying was protein. The two large fractions of muscle protein, the sarcoplasmic and myofibrillar fractions, were measured biochemically. Protein in the myofibrillar fraction, which formed the greater part of the total protein, decreased during the study period. There was no evidence to support the proposal that sarcoplasm in muscle acts as the main reserve of proteins.
Proper Studies and the Art of the Soluble
Authors: TAYLOR L. R.
Published: April 2008

The Art of the Soluble

‘No scientist is admired for failing in the attempt to solve problems that lie beyond his competence.

If politics is the art of the possible, research is surely the art of the soluble. Both are immensely practical‐minded affairs.

Good scientists study the most important problems they think they can solve. It is, after all, their professional business to solve problems, not merely to grapple with them.

That is why some of the most important biological problems have not yet appeared on the agenda of practical research.’

Proper Studies

‘Atoms are immeasurably less complicated than man. And yet nobody who is not professionally a physicist would venture to discuss the nature of atoms. Where man is concerned. the case is different.’
Geese and their future fortune
Authors: OWEN MYRFYN , BLACK JEFFREY M.
Published: April 2008

Wild goose populations were probably limited by winter food supplies before Man modified their winter range and effectively removed that limitation on population growth. At the same time, reduction of hunting lowered Man‐induced mortality and allowed most populations to increase both in Europe and in North America.

This paper considers likely future trends, and, using the population of Barnacle Geese breeding in Svalbard as an example, suggests how numbers might be regulated in a density related manner. The Svalbard Barnacle Goose population has shown a decline in recruitment rate and an increase in the natural mortality rate as numbers have increased. Both of these are reflections of competition on the breeding grounds, though there may be some effects at other times. We suggest that most populations will eventually be limited by resources on the breeding area.

Some of the implications of changes in numbers are that pair‐bond stability and breeding area philopatry are less advantageous and in time will become less pronounced as the selective value of these traits are diminished.

We argue that both for applied reasons (conservation, crop damage prediction) and for academic investigations of population processes, long‐term studies are vital in the management and understanding of goose populations. A number of features of their life history make geese very suitable subjects for such studies.
Greenshanks Tringa nebularia and long‐term studies of breeding waders
Authors: THOMPSON P. S. , THOMPSON D. B. A.
Published: April 2008

Despite great variation in breeding, social and migration systems, there have been few long‐term (more than 5 years) studies of waders. This paper describes a 27‐year study of breeding Greenshanks Tringa nebularia, and briefly reviews the scope for long‐term work on breeding waders in the Western Palaearctic.

Between 1964 and 1990 a Greenshank population in NW Scotland varied threefold in number but declined during the 1980s. Some territories were occupied almost every year whereas others became unoccupied. The increase up to the mid 1970s coincided with good summer weather likely to improve breeding success and subsequent adult recruitment. The decline occurred despite no adverse change in weather, an increase in over‐winter numbers on British and Irish estuaries, and no increase in nest predation. Afforestation in the Flow Country of northern Scotland may have exacerbated the decline by reducing numbers of potential recruits from what were once productive areas. Habitat for broods has deteriorated considerably in the study area because of the impact of all‐terrain vehicles: pool complexes have deteriorated to a greater degree in unoccupied than in occupied territories. Territories with most disturbance have been occupied less regularly. There has been a decline in habitat structural complexity likely to render chicks more prone to predation and less likely to find preferred food. Habitat is now set to recover, and predictions are made about the Greenshank's response.

Of 47 wader species breeding regularly in the Western Palaearctic, none have had lifetime reproductive success measured and long‐term population dynamics have been studied in only nine. We provide a list of species that might be appropriate for addressing six important ecological issues. Five emerge as common targets for further long‐term work: Dotterel Charadrius morinellus, Lapwing Vanellus vanellus, Avocet Recurvirostra avosetta. Common Sandpiper Actitis hypoleucos and Curlew Numenius arquata.
Buoyancy and its constraints on the underwater foraging behaviour of Reed Cormorants Phalacrocorax africanus and Darters Anhinga melanogaster
Authors: HUSTLER KIT
Published: April 2008

The effects of changing buoyancy on the diving and feeding behaviour of Reed Cormorants Phalacrocorax africanus and Darters Anhinga melanogaster was investigated at Lake Kariba, Zimbabwe. A qualitative model of the energetic constraints caused by buoyancy changes on the diving behaviour of these two birds is presented and the predictions from the model are tested. The buoyancy of both species declined exponentially at different rates with water depth. Reed Cormorants were neutrally buoyant at 5–6 m while Darters were neutrally buoyant at 2–4 m depth. Buoyancy changes affect underwater swimming speed, which for Reed Cormorants is twice as fast on the bottom than when commuting, and for the Darter is significantly slower when diving than at any other time. Cormorants feeding in water deeper then 6 m spent less time on the bottom and fed less successfully than those birds feeding in shallower water. This is because their bottom times were significantly reduced as a result of the energetic constraints caused by changes in their buoyancy.
The biannual primary moult of Willow Warblers Phylloscopus trochilus in Europe and Africa
Authors: UNDERHILL L. G. , PRYS‐JONES R. P. , DOWSETT R. J. , HERROELEN P. , JOHNSON D. N. , LAWN M. R. , NORMAN S. C. , PEARSON D. J. , TREE A. J.
Published: April 2008

The Willow Warbler Phylloscopus trochilus is one of the few bird species that undergoes two primary moults a year, a post‐nuptial moult in the breeding area and a moult in the wintering area. Primary‐moult data for Willow Warblers from Finland, Sweden, Britain, the Netherlands, Belgium. Guinea‐Bissau, Uganda, Kenya, Malawi, Zambia, Zimbabwe, Botswana and South Africa are analysed. The parameters of primary moult (mean starting date, standard deviation of starting date, and duration) are estimated using the techniques of Underhill & Zucchini (T.988 Ibis 130: 358–372) and Underhill, Zucchini & Summers (1990 Ibis 132: 118‐12 3). The scheduling of moult in relation to theother main components of the annual cycle, breeding and migration, is considered. The mean durations of post‐nuptial moult for P. t. trochilus and P. t. acredula are 36.5 and 38.3 days, respectively; the start and termination of moult for P. t. trochilus are about 3.5 days later for each degree of latitude northwards, and the start and termination of moult for P. t. acredula, are about 10 days later than that of the most northerly populations of P. t. trochilus studied. Females start their postnuptial moult about 10 days later than males. Southward migration commences as soon as post‐nuptial moult is complete. There is an increasing constraint on the timing of breeding and post‐nuptial moult events at higher latitudes, leading to overlap between them. The duration of pre‐nuptial moult is longer than that of post‐nuptial moult, and is completed shortly prior to northward migration.
The Moreau ecological overview
Authors: FRY C.H.
Published: April 2008

Biological conservation is increasingly concerned with advocacy and lobbying. But its practical politics must stand on a firm basis of scientific fact and understanding: about the behaviour and ecology of species and about the workings of the habitats that are their life‐support systems. For Africa, a solid foundation was laid by R.E. Moreau in two scholarly analyses of the continent and its birdlife:The Bird Faunas of Africa and its Islands(1966) andThe Palaearctic‐African Bird MigrationSystems (1972). Hence the title of this paper: a generation having passed, my objectives are to emphasize the salient observations of Moreau (1972), and to review subsequent changes in the face of Africa as they might affect migrant birds from the Palaearctic that winter there
Perspectives on Palaearctic and Nearctic bird migration; comparisons and overview of life‐history and ecology of migrant passerines
Authors: MÖNKKONEN M. , HELLE P. , WELSH D.
Published: April 2008

In this paper we compare ecological attributes of tropical migrant passerines from the Nearctic and western Palaearctic, focusing particularly on habitat association patterns during both breeding and wintering seasons. Three regions were compared: Europe, western and eastern North America. Breeding bird census data from 32 studies (each including at least four stages of forest succession) were used to assess the association patterns of breeding habitats among tropical migrants. For each species we calculated an index of habitat diversity and habitat preference.

Tropical migrants preferred earlier successional stages than other birds in Europe. The opposite was true in eastern North America. In eastern North America, tropical migrants tended to be associated with a smaller range of serai stages than other passerine species. In their winter quarters, Palaearctic migrants live primarily in open habitats, such as savannas, whereas eastern Nearctic migrants make more frequent use of evergreen forests. Migrants from western North America show the greatest match between breeding and wintering habitats.

We relate the results to the taxonomy and probable history of contemporary avifaunas and vegetation formations of the Old and New World. Taxonomically, tropical migrants from different parts of the Holarctic are less closely related to each other than residents and short‐distance migrants. Tropical and temperate avifaunas are more closely related to each other in the New World than in the Old World. Conservation implications of the between‐continent differences are briefly discussed.
The genetics of bird migration: stimulus, timing, and direction
Authors: BERTHOLD PETER , HELBIG ANDREAS J.
Published: April 2008

The extent to which genetic factors are directly involved in the control of bird migration and the mode of inheritance involved has been studied systematically over the past 15 years in the Blackcap Sylvia atricapilla by cross‐breeding and selective breeding. Results have also been obtained from a few experimental and field studies on Robins Eritfiacus rubecula, Blackbirds Turdus merula and Song Sparrows Melospiza melodia. Cross‐breeding of migrants with nonmigrants has resulted in the partial transmission of migratory activity into the F, generation indicating that the urge to migrate is inherited and is based on a multilocus system with a threshold for expression. Migratoriness and sedentariness in obligate partial migrants is probably inherited in a similar way, suggesting that the decision to migrate also has a strong genetic basis. Both traits can be selected to phenotypic uniformity within 3–6 generations indicating an extremely high evolutionary potential. Orientation behaviour can also be transmitted to the offspring of a nonmigratory population by cross‐breeding. Cross‐breeding individuals with different migratory directions produced offspring with phenotypically intermediate directional preferences, suggesting that the migratory direction is also a predominantly heritable character. In the current development of novel migratory habits in those Central European Blackcaps that now winter in the British Isles, the inheritance of the novel migratory direction may be crucial. Genetic variation in migratory events seems to be sufficient to allow for many microevolutionary processes.
Recent prospects on trans‐Saharan migration of songbirds
Authors: BAIRLEIN FRANZ
Published: April 2008

Many palaearctic migrants in tropical Africa have to cross the inhospitable land of the Sahara desert. Moreau (1961, 1972) hypothesized that these migrants crossed the Sahara in a single non‐stop flight. Recent field data, however, revealed that some migrants stop‐over in suitable desert habitats. The majority of grounded migrants showed a high body‐mass and fat‐loading, indicating sufficient reserves for onward flights. Further evidence on resting periods, retrapping rates and experiments with caged migrants supports the hypothesis of an intermittent migratory strategy, with regular stopovers during the day and flight at night, for some desert‐crossing passerines.
Migration patterns and habitat use by passerine and near‐passerine migrant birds in eastern Africa
Authors: PEARSON DAVID J. , LACK PETER C.
Published: April 2008

Palaearctic migrant passerines and near‐passerines which visit eastern Africa can be divided into six groups based on the latitude of their final wintering area. Species wintering further north in Africa tend (a) to breed in more southern parts of the Palaearctic, (b) to prefer drier habitats and (c) to feed more from the ground than those wintering further south. Many species use quite narrow passage routes through eastern Africa and, for some species, passage is centred further east in spring than in autumn. Southward migration can take more than 4 months from the Palaearctic breeding grounds and many birds stopover in the northern tropics from September to November. By contrast, the return migration takes only about 6 weeks. The timing and strategy of migration within Africa can be broadly related to seasonal patterns of rainfall and vegetation.
Recent trends in breeding populations of some common trans‐Saharan migrant birds in northern Europe
Authors: MARCHANT JOHN H.
Published: April 2008

Population trends of some common trans‐Saharan migrant birds, mostly passerines, were investigated using data from breeding census schemes in five northern European countries during the periods 1976‐89 and 1981‐89. Overall, census data for the 14 species censused in all five countries show about equal numbers of increases and decreases. This is not as expected from the work of Berthold et al. (1986) for birds breeding and on migration in central Europe. Comparison of results between national schemes shows no evidence for overall differences in trends. Correlations in census results between the different schemes, species by species, were mainly positive. For all five countries, there were more positive than negative correlations between year‐to‐year population changes and an appropriate measure of African rainfall.
Habitat selection and diet of Great Snipe Gallinago media during breeding
Authors: LØFALDLI L. , KÅLÅS J. A. , FISKE P.
Published: April 2008

The Great Snipe Gallinago media is considered to be an endangered species. This paper examines its food and habitat use on a sub‐alpine/low‐alpine breeding area in central Norway. It was estimated that earthworms constitute more than 90% of Great Snipe food (by weight). Feeding birds selected the low herb willow scrub vegetation community and to a lesser degree eutrophic fen. Birds did not selectively feed on eutrophic dwarf birch/juniper heath despite it being the third most used vegetation community by virtue of its extent. Although soil penetrability, vegetation cover and earthworm density varied across vegetation communities, Great Snipe selected sites with similar habitat characteristics in different vegetation communities. Great Snipe seemed to select for an optimal combination of soil penetrability and earthworm density, and for medium scrub cover. Nests were found in a broad range of vegetation communities, but only low herb willow scrub was selectively used. However, an equal number of nests was found in eutrophic fen due to its larger extent. Dense vegetation cover around nests and short flushing distance of incubating females indicate low sensitivity to disturbance. We consider the Great Snipe to be a food and habitat specialist, requiring habitats rich in sub‐surface invertebrates to breed. This may explain its scattered distribution in Scandinavia, and may render it vulnerable to habitat modification and loss.
Mating system and laying date in birds
Authors: YOM‐TOV YORAM
Published: April 2008

The hypothesis that polygynous species start breeding later in the season than monogamous ones was examined using two data sets, each with both monogamous and polygynous species—the eight species of wrens which breed in the USA, and five genera (15 species) of British passerines. Comparisons were made within each of 16 states in the USA from which data were available and for each genus in Britain. The hypothesis is supported for most subsets of data, but in some cases polygynous and monogamous species start breeding at the same time (but in no case do polygynous breed earlier than monogamous species). The late breeding of the polygynous species is probably an outcome of the fact that polygynous males tend to participate less in nest activities than monogamous ones.
Evidence from hatching success and DNA fingerprinting for the fertility of hybrid Pied × Collared Flycatchers Ficedula hypoleuca × albicollis
Authors: GELTER H.P. , TEGELSTRÖM H. , GUSTAFSSON L.
Published: April 2008

The Pied and Collared Flycatchers Ficedula hypoleuca and F. albicollis hybridize on the Baltic islands of Öland and Gotland. Field studies of hatching success in clutches from 36 breeding hybrid males indicate that male hybrids reproduce successfully. In comparison, 25 hybrid females had normal clutch sizes but failed to hatch nestlings, suggesting female hybrid sterility. The paternity of seven hybrid males was investigated by DNA fingerprinting using two hypervariable minisatellite probes. Of these hybrid males, six were assessed as fertile. Three of the hybrid male families (43%) contained nestlings with extra‐pair paternity and the frequency of extra‐pair fertilization among 37 nestlings was 22%. One nestling originated from intraspeciflc female nest parasitism. The sterility pattern in hybrids between these two flycatchers with sterile female and fertile male hybrids is in agreement with Haldane's rule.
Ontogeny of food storing in titmice Parus spp.
Authors: HAFTORN SVEIN
Published: April 2008

The ontogeny of food storage in Crested Tits Parus cristatus and Willow Tits P. montanus starts during the period of parental care after the young have left the nest and develops gradually. In southern Norway, the storing behaviour becomes fully developed during August‐September, i.e. at a time when most juveniles have completed their dispersal period and settled in permanent winter flocks. The food storing behaviour is largely innate, but is improved by practice and experience.
No overlap in song repertoire size between yearling and older Starlings Sturnus vulgaris
Authors: EENS MARCEL , PINXTEN RIANNE , VERHEYEN RUDOLF FRANS
Published: April 2008

We recorded the song of 25 male Starlings Sturnus vulgaris to investigate differences in song characteristics between yearling and older males. Older males had significantly larger repertoire sizes and sang significantly longer average song bouts than yearling males. Since older males had almost twice as large a repertoire size as yearling males and since there was no overlap in repertoire size between yearling and older males, our data indicate that the repertoire size of Starlings increases after the first year of life. The largest difference between yearling and older males occurred in the ‘variable song types’ which are the song types containing most of the heterospecific imitations sung in a song bout.
A new species of Phylloscopus warbler from central China
Authors: ALSTRÖM PER , OLSSON URBAN , COLSTON PETER R.
Published: April 2008

A new species of leaf warbler (Sylviidae: Phylloscopus) is described from the mountains of central China. Morphologically it is slightly, yet significantly, different from the partly sympatric P. (proregulus) chloronotus. However, both song and calls are very different, and playback tests elicited no response from either species to the other's song. There are also differences in habitat preference and breeding biology of the two species.
Nest orientation and hatching success of Black Kites Milvus migrans in Spain
Authors: VIÑUELA JAVIER , SUNYER CARLOS
Published: April 2008

An analysis of the orientation of 182 nest sites of the Black Kite Milvusmigransin two areas in south and central Spain found that orientations toward the east were preferred. In southern Spain an analysis of the relationship between nest orientation and hatching success showed that success was lower among the nests located in non‐preferred orientations, with some inter‐annual variation. The tendency to orientate nests toward the east was greater among the early nesting pairs and the effect that the orientation had on the hatching success was also greater than in late nesting pairs. The data suggest that rainfall and prevailing winds were the main factors conditioning nest orientation.
Breeding biology of the Kakapo Strigops habroptilus on Stewart Island, New Zealand
Authors: POWLESLAND R. G. , LLOYD B. D. , BEST H. A. , MERTON D. V.
Published: April 2008

Breeding biology of radio‐tagged Kakapo Strigops habroptilus on Stewart Island was investigated from 1977 to 1988. Some males moved several kilometres from their ranges occupied in the non‐booming season (May‐November) to track‐and‐bowl systems. Occupancy of track‐and‐bowl systems varied markedly from one booming season (December‐March) to another, from no visits in some booming seasons to breeding years when most males occupied their systems nightly. Descriptions and rates of calling for three types of calls by males are given. Breeding probably occurred in 1978, and nests were found in 1981 and 1985, but radio‐tagged females did not nest in 1982‐84 and 1986‐88. Females visit males at track‐and‐bowl systems for mating in mid‐summer (January‐February), and then returned to their home ranges to nest. Nests were under thick vegetation, in short holes in banks or rotten trees at ground level. Clutches consisted of 2–4 eggs, and incubation lasted about 25 days. One female left her eggs and young nestling unattended at least once a night for 1–4 hours. Thus, Kakapo eggs and young chicks were very vulnerable to predation by introduced predators. There was no evidence that any male assisted a female during incubation or nestling‐rearing phases. The chicks were brooded by day until about 30 days old, after which the female roosted nearby. The chicks left the nest at about 10 weeks old, but remained nearby for a further month. Phenological observations of Kakapo food plants suggest that to stimulate and sustain breeding, Kakapo on Stewart Island are dependent upon abundant fruit from a few irregularly mast‐fruiting tree species.
The incidence of the tick parasiteIxodes uriaein KittiwakeRissa tridactylacolonies in relation to the age of the colony, and a mechanism of infecting new colonies
Authors: DANCHIN E.
Published: April 2008

KittiwakesRissa tridactyla(683 chicks and 64 adults) were examined for ectoparasites in three breeding areas: Isle of May (Firth of Forth, Scotland; eight colonies of approximately known age of occupation on natural sites), North Shields and Gateshead (Tyne and Wear, England; well established colonies of known age on buildings). All the 208 ticks collected wereIxodes uriae.On the Isle of May, a colony which had only been established for 7 years was already infested by ticks. Tick incidence increased significantly with the length of colonization of the area during the first 30 years. Age of colonization did not have an effect after 30 years. In Gateshead only a single adult among the 127 birds examined had a tick. No ticks were found on the 106 chicks born at North Shields checked in 1987 or in 1988. However, among nine visiting newly‐fledged chicks from neighbouring colonies caught at the North Shields colony, six had either ticks or scars of previous infestation. Some visiting chicks remained for several days in the host colony and were even fed by the owners of visited nests.Ixodes uriaemay thus spread from one colony to another during visits of newly‐fledged infested chicks to neighbouring colonies. The absence of any infestation in old colonies (38 years in North Shields and 17 years in Gateshead) on buildings that are regularly visited by newly fledged infested chicks, suggests that buildings may lack the rock refuges necessary for tick survival from one year to the next. In this respect Kittiwake colonies on buildings are rather atypical.
Effects of mate removal on the behaviour and reproductive success of Reed Warblers Acrocephalus scirpaceus
Authors: DUCKWORTH J. W.
Published: April 2008

The Reed Warbler Acrocephalus scirpaceus is a largely monogamous insectivorous passerine in which males and females provide equal care by day to eggs and chicks. Polygyny occurs occasionally, with males leaving one female unaided. When females were temporarily removed from three recently‐completed clutches their males deserted and resumed the high song levels typical of unmated males. Males may desert either because they are physically incapable of incubation or because the energy expenditure needed for a male to return to an equivalent stage in the breeding cycle is much lower than for a female to do so. Widowed females (n = 7), however, continued the breeding attempt alone, with similar incubation levels but higher provisioning rates than those of control females. In three out of four mid‐season broods raised by lone females all fertile eggs were reared to healthy fledglings (in the fourth brood the female died), while only one of four late‐season nests produced any fledglings (which were underweight). Late‐season control nests were as successful as earlier ones. Loss of male help led to starvation of chicks, but caused no adverse effects during incubation. This explains the small changes in widows' sitting levels during incubation, but much greater effects after hatching. Females may need male help to rear late broods (but not early broods) as days are shorter and food is scarcer. Males may normally help at nests, even those in the mid‐season, because in stressful spells (even for a few days) such help is vital for successful breeding but in good periods it costs the male little.
The increase in risk of predation with begging activity in broods of Magpies Pica pica
Authors: REDONDO TOMAS , CASTRO FRANCISCA
Published: April 2008

Begging activity in broods of Magpies Pica pica was measured as the average total number of begging nestlings and the number of nestlings giving begging calls between 5 and 9 days since the first nestling hatched. There was considerable between‐brood variation in begging activity relative to day‐to‐day variation within broods. Predation between 7 and 20 days of age was more frequent among those broods which had not previously suffered from brood reduction due to nestling starvation. Broods which were preyed upon showed significantly higher levels of begging activity than broods of a comparable size that were not preyed upon. In addition, the time elapsed from hatching to predation showed a negative correlation with the total number of begging nestlings. Within broods, those nestlings with the highest begging motivation (measured as the latency to respond when stimulated) seemed to be more readily taken by predators. These results confirm the existence of costs associated to begging in the form of an enhanced risk of being detected by predators.
A comparison of digestive efficiency in birds of prey
Authors: BARTON NIGEL W. H. , HOUSTON DAVID C.
Published: April 2008

Differences in how raptors hunt and what they catch are correlated with size‐independent differences in length of the small intestine, the region of the digestive tract responsible for food absorption. The study examined the functional significance of these differences among ten raptor species. Dry matter apparent digestive efficiency was calculated for each species fed a diet of day‐old cockerels. For Falconiformes and Strigiformes, efficiencies varied between 75% and 82%, digestive efficiency being positively correlated with intestine length.

Generalist species, with a wide prey spectrum and feeding on relatively easily caught prey and carrion, had long intestines and high digestive efficiencies. Raptors specializing on fast‐moving, avian prey had short intestines and reduced digestive efficiency. The Peregrine Falco peregrinus and the Common Buzzard Buteo buteo were used as examples of specialist and generalist feeders, respectively. Rabbit and pigeon were fed to both. Buzzards digested both diets more efficiently than Peregrines. Body‐mass changes were used to examine the nutritional value of the two diets to each species. Buzzards gained body‐mass when eating rabbit, Peregrines lost mass. Both species gained mass when feeding on pigeon. It seems that consideration of diet quality, not just quantity, is essential in understanding raptor food requirements. Generalist raptors have high efficiencies on several diets, specialists compensate for their reduced efficiency by eating food of high nutritional quality. Various aspects of prey quality are examined.
Diel activity of resident and immigrant waterbirds at Lake Turkana, Kenya
Authors: FASOLA M. , CANOVA L.
Published: April 2008

Of the 42 dominant species of waterbirds at Lake Turkana, Kenya, 14 foraged uniformly throughout the day and night, five foraged mostly during the night, five foraged during both the night and day but with diurnal peaks, 17 were exclusively diurnal and only one was exclusively nocturnal. Species with uniform feeding activity usually captured small prey, using tactile or visual plus tactile cues; most diurnal species captured large prey, using visual cues. However, some species which fed mostly at night, or uniformly, relied exclusively on visual cues. We found support from only one species that moonlight influenced foraging activities. Palaearctic immigrants spent significantly more time foraging than partial migrants and residents; they were also smaller and mainly microphagous. Only gulls and terns were restricted to diurnal feeding, presumably by their need to see and capture prey while flying. The other groups were formed by species which foraged uniformly over 24 h or partially by day or night. These patterns indicate that in most waterbirds feeding activities are not basically tied to any phase of the diel cycle. Since most waterbirds display some degree of nocturnal activity, time budget studies based only on diurnal observations are likely to be misleading.
Factors influencing food‐load sizes brought in by Shags Phalacrocorax aristotelis during chick rearing
Authors: WANLESS S. , HARRIS M. P. , RUSSELL A. F.
Published: April 2008

Weights of food loads brought back to the colony by 26 Shags Phalacrocorax aristotelis rearing chicks were determined using the water‐offloading procedure. Loads consisted almost entirely of lesser sandeels Ammodytes marinus. Load size was extremely variable, ranging from 8 to 208 g with a mean load weight of 106 g. Data on foraging behaviour collected concurrently demonstrated that Shags brought back heavier loads when they were feeding farther away from the colony and when brood biomass was larger. These two variables together explained 70.3% of the variation in load size. We postulate that adults had already digested their own food requirements by the time they arrived back at the nest, and the contents of the loads were therefore primarily for the young. On 67% of trips, Shags caught, on average, more than one fish per dive. This estimate ignores the food requirements of the adult, and therefore true prey‐capture rates must have been higher.
Flock feeding and food intake in Little Egrets Egretta garzetta and their effects on food provisioning and reproductive success
Authors: HAFNER H. , DUGAN P. J. , KERSTEN M. , PINEAU O. , WALLACE J. P.
Published: April 2008

Food provisioning to chicks of Little Egret Egretta garzetta in a colony at Ligagneau in the Camargue, southern France, was measured using electronic nest balances. Both pair members supplied food to the chicks, and each performed three to five alternating foraging trips.

The loading rate during the first trip of the day (1.09 g/min) was more than three times as high as that during later trips (0.32 g/min) and accounted for 20% of the daily amount of food delivered. This food was collected while the birds were feeding in dense aggregations on mosquitofish which had become temporarily concentrated due to hypoxic conditions overnight in the surrounding marsh. Later in the day, when this concentrated food source was no longer available, the birds fed solitarily.

The total amount of food delivered per day remained constant at 385 g as chick age increased from 10 to 20 days. Given the observed loading rates, 385 g is near the maximum amount of food the pair can deliver during a 16.5‐h daylight period when they forage continuously throughout the day but only one parent at a time. This indicates that a time constraint limits the amount of food delivered to a brood during this stage of the breeding cycle. Given this time constraint, the total amount of food delivered per day would have been reduced by 25% if the birds had not been able to benefit from the concentrations of mosquitofish during the early morning.

Breeding success was significantly higher at Ligagneau (3.25 chicks/nest) than in other Camargue colonies (2.69 chicks/nest). In addition, post‐fledging survival of chicks with a low rank in the brood hierarchy was probably better at Ligagneau than elsewhere in the Camargue. We attribute this elevated reproductive output at Ligagneau to the exceptionally large amount of food collected by egrets during the early morning aggregations, which were probably formed in response to predictable concentrations of mosquitofish in the permanent marshes surrounding this colony. Such aggregations were rarely observed in the temporary marshes surrounding the other colonies, probably because the occurrence and location of fish concentrations are difficult to predict in this habitat due to rapidly falling water levels.
Adult survival and numbers in a coastal breeding population of Redshank Tringa totanus in northwest England
Authors: THOMPSON PATRICK S. , HALE W. G.
Published: April 2008

The results of a long‐term capture‐mark‐recapture ringing programme carried out on a coastal population of breeding Redshanks Tringa totanus between 1974 and 1988 are presented.

Both sexes were equally likely to be recaptured in subsequent years, as were birds captured for the first time compared with those that had been captured previously. Older birds were more frequently recaptured than were young birds. There was no significant difference in male and female adult survival rates, with a mean of 72% of females and 75% of males surviving each year.

The breeding population fluctuated annually with estimated breeding densities of 122–285 pairs per km2. Variation in breeding numbers (males), but not survival, was partially attributable to winter air temperature.
The breeding biology and causes of nest failure of Scottish Black‐throated DiversGavia arctica
Authors: MUDGE G. P. , TALBOT T. R.
Published: April 2008

The breeding biology and causes of nest failure were examined for Black‐throated DiversGavia arcticain core areas of their Scottish breeding range in 1983–1987. Breeding was confirmed for up to 88% of territorial pairs each year (n= 28–62), and 76% of nests were on islands. Hatching success was consistently low with, on average, only 43% of territorial pairs managing to hatch a clutch each year; 64% of recorded nest failures occurred during the first week of the 4‐week incubation period.

Overall breeding success in West Sutherland in 1984–1987 averaged 0.23 chicks per territorial pair per year, while in Ross‐shire for 1986–1987 it was 0.29. Forty percent of hatched chicks survived to fledge, and 92% of recorded deaths occurred in the first fortnight after hatching; 4.8% of fledged broods held two chicks.

Causes of nest failure were assessed with the aid of surveillance cameras. Approximately 30% of losses were due to water level changes (mostly floods), 48% to predators (primarily nocturnal mammals, but also Hooded CrowsCorvus corone), 13% to human egg collectors and 5% to desertion following human disturbance.

Scottish Black‐throated Divers produce only half the number of chicks tentatively estimated to be required to maintain a stable population. The main difference between the Scottish and more successful Swedish populations is in the degree of chick mortality.
Moult in Black‐browed and Grey‐headed Albatrosses Diomedea melanophris and D. chrysostoma
Authors: PRINCE P. A. , RODWELL S. , JONES M. , ROTHERY P.
Published: April 2008

We recorded the age of individual wing and tail feathers of Black‐browed and Grey‐headed Albatrosses Diomedea melanophris and D. chrysostoma of known age and breeding status at Bird Island, South Georgia. Breeders and non‐breeders of both species moult their rectrices annually. Non‐breeders moult primaries biennially. In the first year of a cycle, the outer three and some inner primaries are moulted descendantly; in the next year the inner primaries are moulted ascendantly, starting from primary seven. There is a general progression to moulting equal numbers of primaries in each half of the cycle by the time breeding starts at about 10 years of age. Grey‐headed Albatrosses usually moult fewer primaries than Black‐browed Albatrosses, particularly as 3‐year‐olds, when they undertake substantial plumage change in body moult. Most secondaries in Black‐browed Albatrosses have been replaced once by age 4 years. Breeding Black‐browed Albatrosses continue the moult pattern established as immatures whether they fail or not, as do failed Grey‐headed Albatrosses. Successful Grey‐headed Albatrosses, which breed again 16 months later, moult their three innermost primaries after breeding in the remainder of the current year and, after a period when moult is interrupted, renew the remaining primaries the following year. Comparisons between species and between failed and successful birds within species indicate that moult rate is not closely linked to the length of the interval between breeding attempts. Interspecies differences are better explained by breeding latitude, with tropical albatrosses moulting twice as fast as sub‐Antarctic species, possibly reflecting food availability outside the breeding season.
Migration, stopover and moult of the Great Reed Warbler Acrocephalus arundinaceus in Ghana, West Africa
Authors: HEDENSTRÖM ANDERS , BENSCH STAFFAN , HASSELQUIST DENNIS , LOCKWOOD MARY , OTTOSSON ULF
Published: April 2008

We studied Great Reed Warblers Acrocephalus arundinaceus at two localities in Ghana during the winter. In the north (Tono), the birds arrived from late September and conducted a rapid moult soon after arrival. Towards the end of moult, birds accumulated fat and disappeared from the site. In the south (Tafo), birds arrived from mid‐November in fresh plumage. This seemed to be the final wintering area as birds stayed there during the winter. In March‐April they again accumulated fat, although only small amounts, before spring migration back to breeding areas.
Breeding ecology of the Aquatic Warbler Acrocephalus paludicola on the Biebrza marshes, northeast Poland
Authors: DYRCZ ANDRZEJ , ZDUNEK WANDA
Published: April 2008

Aquatic Warblers Acrocephalus paludicola were studied in a natural fen mire in the Biebrza River valley, the main breeding ground of the species in its entire distribution range. The number of males present and singing at the sample plot changed considerably during the breeding season. Individual identified colour‐ringed males sang with unchanged intensity throughout the breeding season. The period of daily singing activity differed from other species of Acrocephalus; males sang at dusk rather than at dawn. Males took no part in rearing nestlings but remained on territory and showed vigilance behaviour. The density of males in the breeding season ranged from 1.0 to 10.9 per 10 ha. The density of nesting females ranged from 1.3 to 15.7 per 10 ha. In the most suitable habitat females were more numerous than males. The distribution of females (nests) was clumped where potential food resources were higher. Nests were well hidden in places with deeper water between sedge tufts and an abundance of old dry sedge. Females feeding nestlings collected most food within a 5–60‐m radius (mean 31.7 m). The return rate of males was higher than that of females. The results suggest a mating system that is intermediate between facultative polygyny and promiscuity.
The song of the Seychelles Warbler Acrocephalus sechellensis, an island endemic
Authors: CATCHPOLE CLIVE K. , KOMDEUR JAN
Published: April 2008

The Seychelles Warbler Acrocephalus sechellensis is a resident, cooperative breeder in a saturated, island environment, whose song structure diners significantly from European marshland Acrocephalus species. The song is transmitted within a more restricted frequency range, that which propagates most effectively through tropical forest. The Seychelles Warbler has developed a relatively short, simple song, used for territorial defence throughout the year, which is readily elicited by playback. Yet it also has a complex repertoire of song types, and song activity peaks before and declines during breeding, suggesting a sexual function. The demands of tropical island life are thus reflected in both the structure and function of song in the Seychelles Warbler.
Habitat segregation and the insular syndrome in two congeneric raptors in New Caledonia, the White‐bellied Goshawk Accipiter haplochrous and the Brown Goshawk A. fasciatus
Authors: THIOLLAY JEAN‐MARC
Published: April 2008

The comparative distribution and abundance of the two congeneric goshawks of New Caledonia, the White‐bellied Goshawk Accipiter haplochrous and the Brown Goshawk A. fasciatus vigilax, were studied on 100 1‐km2 sample quadrats spread randomly over the island. The White‐bellied Goshawk is a well‐differentiated endemic forest‐dwelling species, presumably of older origin than the morphologically little‐differentiated island subspecies of the Brown Goshawk, which is restricted to open habitats. The two species exhibit ecological characteristics attributed to the so‐called insular syndrome; these characteristics were more pronounced in the White‐bellied than in the Brown Goshawk. The densities of both species were much higher than any density of the same or similar species ever recorded on a continent. Their habitat and foraging niches were broad. The two species were clearly segregated by habitat, their distribution overlapping only in semi‐forested lowland areas where the White‐bellied tended to encroach more on the habitat of the Brown Goshawk than the reverse. Possible determinants of their abundance, niche breadth and interspecific segregation are discussed, as well as the consequences for their conservation. The occurrence in New Caledonia of two additional congeneric species recently extinct and the existence of three other pairs of congeneric bird species with similar relationships are also emphasized.