bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparative study of the breeding success of Whooper SwansCygnus cygnusnesting in upland and lowland regions of Iceland
Authors: REES E. C. , BLACK J. M. , SPRAY C. J. , THORISSON S.
Published: April 2008

The study assessed the reproductive success at different stages of the breeding season of Whooper SwansCygnus cygnusfrom two geographically distinct areas of Iceland, one an upland and the other a lowland region. Censuses made at both sites indicated that the majority of the birds did not attempt to breed and that annual recruitment came from 30 to 40% of the population. Individual females tended to lay more eggs in the lowlands, with a mean clutch‐size of 4.7 eggs, compared with 3.8 eggs per clutch in the highlands. A mean brood‐size of 3.1 cygnets was obtained at both the highland and the lowland sites in August but the highland cygnets were significantly smaller and lighter. The difference in cygnet size could be attributable to one or a combination of factors including age differences and habitat variables. Lowland adults were significantly heavier than those from the highlands, which reinforced the view that habitat quality was superior at the lowland site. There was no difference in the feather length recorded for adult swans moulting in the two study areas, indicating that the moult occurred concurrently in the highlands and lowlands. The number of cygnets lost per brood between ringing and resighting in the wintering range was significantly higher for the highland swans, although the number of highland families relocated was small. The results indicate that birds from different breeding areas may contribute disproportionately to the percentage of juveniles reared annually in the population.
Eggshell strength in cuckoos and cowbirds
Authors: BROOKER M. G. , BROOKER L. C.
Published: April 2008

Parasitic cuckoos of the genus Clamator and parasitic cowbirds Molothrus spp. lay eggs that appear to be stronger than those of their hosts. Similar differences in eggshell strength between the eggs of the Cuculus/Cacomantis/Chrysococcyx cuckoos and their hosts are not apparent. We suggest that the advantage of a strong eggshell in the Clamator and Molothrus species is to protect the parasite's egg from damage if the nest is multiply parasitized. This suggestion relies on the observation that Clamator and Molothrus species commonly lay more than one egg per nest and often remove or damage eggs in the process.
The daily pattern of autumn bird migration in the northern Sahara
Authors: BIEBACH HERBERT , FRIEDRICH WOLFGANG , HEINE GEORG , JENNI LUKAS , JENNI‐EIERMANN SUSANNE , SCHMIDL DIETER
Published: April 2008

The temporal pattern of migration by passerine birds during the night, and their arrival during the day at the Egyptian coast and in the northern Sahara Desert was investigated. The mean direction of nocturnal migration at the coast was south‐southeast, while at all desert sites it was south‐southwest.

Birds arrived at the Egyptian coast only during the second half of the night which is explained by the fact that no birds could have taken off from the Mediterranean Sea. At least some of the birds landed at the coast where they spent the day before taking off shortly after sunset. These birds passed the desert sites at the expected time of day assuming a ground speed of 18 m per second. However, the origin of the birds passing the desert sites early at night is unclear. They must either have spent the day in the desert north of the study sites or they had overflown the Egyptian coast in the afternoon without landing.

The landing of birds during the day at the desert sites was bimodal. This pattern of arrival is explained either by some birds having landed at the Egyptian coast in the early morning before continuing, or by deteriorating conditions later in the day during flight or when resting in the desert, that obliged them to seek shelter at the desert sites.

A correlation between the number of migrants observed during the night and the number of resting birds in the desert on the following day suggests that an unknown proportion of birds might regularly use an intermittent migratory strategy that includes rest periods by day when crossing the desert, whereas others might adapt a non‐stop migratory strategy.
The breeding performance of the Gentoo Penguin Pygoscelis papua at the northern edge of its range
Authors: BOST C. A. , JOUVENTIN P.
Published: April 2008

Gentoo Penguins Pygoscelis papua on the Crozet Islands have a unique timing of breeding, which occurs in winter and is considerably protracted, differing greatly from that of other populations breeding south of the antarctic convergence. Their breeding biology was intensively studied in 1983–1989, involving daily observations in 1983–1985. Winter breeding is associated with an extension of laying, chick rearing, foraging trips and premoult periods, a lower breeding success and a high weight loss. Annual variations in breeding performances were less pronounced than for southern populations. Variations in breeding success were closely associated with variations in feeding frequencies, fledging and breeding weight, and timing of laying. Early breeders were at an advantage over late breeders in terms of breeding success, growth patterns, fledging weight, duration of foraging trips and premoult period. The unusual winter breeding coincides with a time when food is most readily available for chick rearing in restricted foraging conditions at the edge of the species' breeding range.
Responses of breeding Reed Warblers Acrocephalus scirpaceus to mounts of Sparrowhawk Accipiter nisus, Cuckoo Cuculus canorus and Jay Garrulus glandarius
Authors: DUCKWORTH J. W.
Published: April 2008

Mounts of a Cuckoo Cuculus canorus, a Sparrowhawk Accipiter nisus and a Jay Garrulus glandarius were presented at nests of Reed Warblers Acrocephalus scirpaceus at all breeding stages. Response strength could best be classified according to approach distance (to the mount) and vocalizations used. Warblers reacted much more aggressively to a mount on the nest than to one 3 m adjacent; they approached much more closely, were less likely to sing but often gave a frenzied‐sounding rasp (which was never given to an adjacent mount). Reaction was more aggressive to a Cuckoo, which was often attacked, than to a Sparrowhawk, of which they were wary; response to a Jay was intermediate. Reaction was more aggressive after the clutch had been completed than before. After the brood had fledged, parents still responded strongly to the Jay and Sparrowhawk, but responded to the Cuckoo only briefly before ignoring it. These results are consistent with the Reproductive Value‐Stimulus Value hypothesis. They also demonstrate that Reed Warblers can tell Cuckoos from Sparrowhawks, as can many non‐host species. The close resemblance of these two species is often suggested to be mimicry of the Sparrowhawk by the Cuckoo but, if this is so, it is not successful. Alternatively, the similarity could be mimicry to reduce predation on the Cuckoos themselves, a chance resemblance, or due to similar selective forces acting on both species, as each would presumably benefit from reduced conspicuousness.
Possible effects of local enrichment by gulls on feeding‐site selection by wintering Barnacle Geese Branta leucopsis
Authors: BAZELY D. R. , EWINS P. J. , McCLEERY R. H.
Published: April 2008

The selection of salt‐marsh feeding sites by wintering Barnacle Geese Branta leucopsis was investigated on Schiermonnikoog, The Netherlands. Use of sites by geese was estimated by counts of goose droppings. Geese spent significantly more time grazing in sites with evidence of Herring Gull Larus argentatus and Lesser Black‐backed Gull Lfuscus breeding activity than in nearby non‐gull sites. The nitrogen content of red fescue grass Festuca rubra was significantly greater in gull sites. We suggest that the geese preferred to feed in these locations because of the improved nutritional value of the grass. The higher nitrogen content of F. rubra in gull sites was most likely the result of nutrient inputs from gull droppings rather than goose droppings.
Winter movements and habitat use by Cabot's Tragopans Tragopan caboti in southeastern China
Authors: YOUNG L. , ZHENG G. M. , ZHANG Z. W.
Published: April 2008

The endangered Cabot's Tragopan Tragopan caboti is endemic to the lower montane forests of southeastern China. Three individuals in Wuyanling Natural Reserve were radiotracked over the winter of 1987/88 to study their movements and habitat use. Home ranges varied from 2.9 to 20.0 ha, declining in size in December.

Marked individuals used areas with thick undergrowth, a greater percentage of bare ground, proximity to water sources and a gentle slope. Also selected were areas containing an abundance of fallen nuts of Lithocarpus sp., Cyclobalanopsis (= Quercus) sp. and the seed capsules of Schima superba. The tree Daphniphyllum macropodum was important for roosting and the leaves and fruits were eaten.

Conservation of the Cabot's Tragopan will depend on protection of its remaining forest habitat, including habitat management to ensure the continued availability of the essential habitat features identified in this study.
Relationships between egg size, chick size at hatching, and chick survival in the Whimbrel Numenius phaeopus
Authors: GRANT MURRAY C.
Published: April 2008

The relationships between egg size, chick size at hatching and chick survival in Whimbrels Numenius phaeopus were studied over a three‐year period in the Shetland Isles. Three measurements of chick size at hatching were all positively correlated with egg volume, though the relationship was strongest with hatchling body‐weight. In two of the three years the proportion of chicks from a brood which survived to fledging increased significantly with the mean hatching weight of chicks in the brood. Within broods, a significant effect of hatching weight on survival was detectable only up to 7 days after hatching. Between years the egg volumes and hatchling weights of individual female Whimbrels showed relatively little variability, indicating that these attributes could be controlled to a large extent by inheritance.
Tits and their caterpillar food supply
Authors: PERRINS C. M.
Published: April 2008

In this paper I review what is known about the relationship between the tits' clutch‐size and the timing of their breeding season and the numbers of their caterpillar prey. The results come from the Edward Grey Institute's long‐term study of Great and Blue Tits in Wytham Wood, near Oxford. This study was started in 1947 by Drs D. Lack and J. A. Gibb (Lack 1966, Perrins 1979)‐ These results could only have been obtained from a long‐term study and emphasize the value of such studies for our understanding of certain aspects of ecology. In addition, they could not have been obtained by a study of the birds alone, being dependent on a knowledge of their insect food; most of this information was made available as a result of a parallel long‐term study of the insect fauna of the oak trees, made by a number of people from the Hope Department of Entomology, University of Oxford.
Using long‐term ornithological studies in setting targets for conservation in Britain
Authors: PIENKOWSKI MICHAEL W.
Published: April 2008

Long‐term studies are necessary in conservation work for two main purposes: monitoring of population parameters, and defining habitat requirements to set targets for conservation action. Apart from their intrinsic interest, birds may be of value also as a means of monitoring the wider environment. Current developments include the integration of measures of breeding performance and survival with those of population size. This will also aid early warning of changes. The range of normal variation in these measures needs assessment to identify limits beyond which action is needed. Monitoring studies need to be reported in appropriate habitat or geographical units, but cover as wide a geographical area as possible in a coordinated manner, to provide context. Long‐term studies are required for defining requirements, as needs may vary with overall population size, weather conditions, and other features which differ between years. Population studies based on age‐structures at a moment in time may not be a good approximation of the real performance as assessed by following age‐cohorts through time. This may be especially so in rare species. For these, sample sizes also present problems in short studies. Long‐term studies may be required also to identify the needs of less obvious components of populations, such as immature individuals.
Effects of density‐dependence and weather on population changes of English passerines using a non‐experimental paradigm
Authors: GREENWOOD JEREMY J. D. , BAILLIE STEPHEN R.
Published: April 2008

The Common Birds Census documents changes in the populations of the more abundant British land birds. Here we analyse the CBC data for various English passerines to discover the separate effects of weather and of density‐dependent feedback on their annual population changes. Density dependence is generally apparent in the data from woodland plots, less so in those from farmland. There are clear effects of weather, particularly in farmland. Prolonged snowfall in winter reduces populations of most species; frost and low temperatures appear much less important. Rainfall in March and April increases numbers censused in the spring but this may be an artefact. We discuss ways in which analyses such as these should be taken forward.

We consider whether this work is respectable science, arguing that monitoring through the CBC goes much further than mere surveillance of numbers, that such monitoring is important in wildlife management, and that density dependence is not a bankrupt paradigm. Long‐term data gathering is an essential part of ecological science, even in programmes not designed at the outset to test specific hypotheses.
Sex‐biased mortality in the Lesser Black‐backed Gull Larus fuscus during the nestling stage
Authors: GRIFFITHS R.
Published: April 2008

Theory predicts that skewed progeny sex ratios should be relatively common in vertebrate populations. In most birds this has proved hard to substantiate due to the difficulties associated with identifying the sex of large samples of chicks. This study reports the success of a new molecular DNA technique in determining the sex of 601 newly‐hatched Lesser Black‐backed Gulls Larus fuscus

There was no evidence of any adaptive sex ratio within broods. Male chicks were found to be disproportionately large and to grow at a faster rate than females. The overall sex ratio changed significantly from 0.484 (male/male + female) at hatching to 0.399 by fledging, probably due to male susceptibility to starvation. Mortality also increased significantly with hatching order, an effect often observed in species like the Lesser Black‐backed Gull where hatching is asynchronous. I discuss the possibility that hatching asynchrony may in fact be a strategy employed to prevent excessive skews developing in progeny sex ratio whenever variable differential mortality is likely.

The results appear to vindicate Fisher's (1930) hypothesis which predicts the overproduction of the ‘cheaper’ sex. However, as the skewed sex ratio may be determined more by unpredictable environmental factors, such as food supply and weather conditions rather than parental strategy, this interpretation should be treated with caution.
Effects of DDT on the Fish Eagle Haliaeetus vocifer population of Lake Kariba in Zimbabwe
Authors: DOUTHWAITE R. J.
Published: April 2008

Twenty clutches were collected from nests of Fish Eagles Haliaeetus vocifer at Lake Kariba, Zimbabwe, and a small dam nearby in 1989‐90. Unaltered DDT, and metabolites DDD and DDE, were found in every egg. Mean levels of σDDT(= DDT + DDD + DDE) generally varied from 14 to 49 mg/kg dry weight per clutch, but 113–223 mg/kg dry weight were found in clutches from the eastern end of the lake and the mouth of the Sengwa River. SDDT and DDE levels were significantly correlated with the Ratcliffe Index of eggshell thickness. Comparison with museum specimens showed that the Ratcliffe Index has declined by 11% since 1936‐41 due to a significant fall in shell weight. Eggshell thinning exceeded 20% at the eastern end of the lake.

Aerial surveys in 1987 and 1990 found that hatching success along the southern lakeshore exceeded 72%, but chicks were seen in fewer than half the nests at the eastern end. However, the density of breeding pairs was greatest here.

Residue levels have increased by about 8% since 1980, rising more steeply in areas recently sprayed for tsetse fly control and falling in others. The threat from DDT may now be receding as regional use has declined and will end, for tsetse fly control, by 1995. None was used for this purpose in 1991. Mercury levels in adult birds were very high and may pose a significant risk.

The breeding population may be limited by availability of safe nest sites. Chicks are sometimes eaten by people. Settlement along the lakeshore is increasing and safe sites are becoming scarcer as dead trees in the lake collapse and large trees onshore are destroyed by elephants.
On the ecomorphology of migrants
Authors: WINKLER HANS , LEISLER BERND
Published: April 2008

A multivariate analysis of data from a wide range of avian species revealed that migratory distance was related to a high aspect ratio, long and pointed wings and well‐developed distal wing segments. Migration also appeared to set limits on the development of the hind limb and on the wing muscles not involved in forward flight. Among Sylvia warblers it is shown that habitat use and migration may constrain each other.
Conservation of migrants on their breeding grounds
Authors: BIBBY C.J.
Published: April 2008

This paper addresses the question of how to diagnose the causes of a population decline of a migratory bird so that conservation action can be taken. Diagnosis may be through study of habitats or population factors. Different approaches are illustrated with examples from the more threatened migratory species which breed in Europe. Gaps in knowledge of how to make conservation diagnoses and of the circumstances of some of Europe's few migratory and globally endangered birds are shown.
Habitat use by Palaearctic migrant passerine birds in West Africa
Authors: MOREL GERARD J. , MOREL MARIE‐YVONNE
Published: April 2008

Data on passerine migrants in West Africa published since the works of Moreau j 1972) and Curry‐Lindhal (1981) are reviewed and new information on wintering ranges are summarized. An important feature of West Africa as a wintering zone is the presence of the two great river basins of the Senegal and the Niger, which are responsible for the Sahel being far richer than would be expected at this latitude. This ‘paradoxical’ or ‘green’ Sahel is under the threat of agricultural developments and of increasing desertification. Conversely, Palaearctic migrants can take advantage of the new‐savanna/forest mosaics and agricultural developments which have replaced the rain forest.
Population limitation in Palaearctic‐African migrant passerines
Authors: BAILLIE STEPHEN R. , PEACH WILL J.
Published: April 2008

We report the results of key factor analyses for Sedge WarblerAcrocephalus schoenobaenus,BlackcapSylvia atricapilla,WhitethroatSylvia communisand Willow WarblerPftylloscopus Irochilusbased on extensive data from the United Kingdom gathered by the British Trust for Ornithology. These results are compared with those from published key factor analyses based on intensive studies of SwallowsHirundo ruslica,RedstartsPhoenicurus phoenicumsand three populations of Pied FlycatchersFiiedula hypoleuca.Variation in losses between fledging and the following breeding seasonlk4) accounted for most of the variation in total losses (KT) for all populations. Breeding performance was poorly correlated with population changes. Density‐dependence was found mainly in 64, its strength decreasing as average rate of population change increased. There was also evidence of weak density‐dependence in the clutch size of Swallows and in Willow Warbler egg losses. Fluctuations ink4were correlated with conditions on the wintering grounds in Sedge Warblers, Whitethroats and Swallows, for the first two species these relationships being confirmed by analyses of independent survival estimates based on mark‐recapture data. Populations of Sedge Warblers and Whitethroats appear to be limited by competition for resources on the wintering grounds. Removal experiments suggest that Willow Warblers, Pied Flycatchers and perhaps Blackcaps are limited through recruitment to the breeding population, in the case of Pied Flycatchers this limitation being in relation to the availability of nest sites.
Load‐lightening in cooperatively breeding birds and the cost of reproduction
Authors: CRICK HUMPHREY Q.P.
Published: April 2008

Helpers at the nest of cooperatively breeding birds often ‘lighten‐the‐load’ of the breeders, by allowing them to decrease their effort. When the shape of the relationship between survival cost and provisioning effort is concave‐up then a helper incurs only a small increment in mortality, for a given amount of help, but the breeder benefits from a larger fall in mortality. A convex‐up relationship for pre‐breeders may explain why some groups (such as larids) do not breed cooperatively. Load‐lightening could provide significant extra gains to the helper's future indirect fitness by increasing the lifespan and life‐time reproductive success of related breeders.
The breeding biology and population dynamics of King Penguins Aptenodytes patagonica on the Crozet Islands
Authors: WEIMERSKIRCH H. , STAHL J. C. , JOUVENTIN P.
Published: April 2008

Among King Penguins Aptenodytes patagonica at Possession Island, one of the Crozet Islands, the length of the moult period, pre‐laying period, incubating and brooding shifts were highly variable according to the year and to the stage of the breeding season. The moulting period was shorter in late breeders than in early breeders. Only half of the birds which successfully reared a chick bred the following cycle, but late in the season. Almost all these late breeders were unsuccessful. The reasons for the high variability in the breeding pattern observed in this species between years, as well as between colonies and between individuals are discussed. Breeding success was on average 30.6% and survival during the first year at sea could reach 50%. The survival of adult birds has increased during the past 10 years from 90.7% to 95.2% per annum. Despite an almost biennial breeding frequency and a very high rate of chick loss during the winter fast, the King Penguin population of Possession Island has doubled between 1966 and 1985 due to a high survival rate of adult and immature birds. The increase during the last decade in adult survival and in adult and chick condition suggests that the population increase could be the result of an improvement in food availability.
The attendance and absence of adult Kittiwakes Rissa tridactyla from the nest site during the chick stage
Authors: COULSON J. C. , JOHNSON M.P.
Published: April 2008

In recent years there have been indications that the attendance of Kittiwakes Rissa tridactyla at the nest whilst containing young has changed, possibly influenced by food shortage. This paper examines the attendance of parents at the nest at North Shields, England, at a time when the breeding success was high and there was no indication of food shortage. It was evident that there was considerable variation in the attendance of individual parents, and chicks were left alone for the first time between 9 and over 40 days after hatching. Chicks were left alone overnight more frequently than during the day; this is related to the much longer overnight feeding trips by the parents.

The recording method used in this study gave a continuous trace of the presence of each adult, and it has been used to calculate the errors made from spot observations.
Characteristics and utilization of old Black Woodpecker Dryocopus martius holes by hole‐nesting species
Authors: JOHNSSON KRISTINA , NILSSON SVEN G. , TJERNBERG MARTIN
Published: April 2008

Old nest holes made by the Black Woodpecker Dryocopus martius were examined in two study areas in Sweden. We found a large variation in nest hole characteristics and that the height in the tree and depth of the hole were important factors in the choice of nest hole by secondary hole nesters. A large proportion of old nest holes remained unoccupied. Many holes were probably of poor quality due to shallow depth, low height or narrow entrance. Nest holes in the vicinity of farmland (<200 m from the field‐forest edge) were more often occupied than nest holes deeper into the forest. This was because Jackdaws Corvus monedula, the numerically dominant species, only used nest holes near farmland. Jackdaws usually used the best nest holes, while other subordinate species had to use inferior holes near fields or nest holes in areas with less competition, deeper in the forest. Besides birds, some mammals and bees were found using old Black Woodpecker holes.
Food niches of sympatric Marsh Harriers Circus aeruginosas and Hen Harriers C. cyaneus on the Dutch coast in winter
Authors: CLARKE ROGER , BOURGONJE ANDRÉ , CASTELIJNS HENK
Published: April 2008

Analysis of pellets collected from adjacent communal winter roosts of Marsh Harriers Circus aeruginosus and Hen Harriers C. cyaneus on an extensive saltmarsh in the southwest Netherlands showed highly significant differences between the diets of the two species. Marsh Harrier diet showed no change throughout January, February and March. They specialized on ducks, which were about half of their prey numerically and more important by weight. Although Marsh Harriers sampled other prey, this remained at a low level and showed no seasonal response to the availability of young lagomorphs. Hen Harriers occupied the niche of a generalist predator, having a broader diet and responding to the presumed changes in availability of prey with diet shifts. In November, about half of their prey items were passerines but these declined in importance in December, and small mammals rose. The proportions of both small mammals and birds fell in February and March, due to increasing dependence on young lagomorphs. Diet overlap between the two species was greatest in January and declined in February and March.
Differences in the onset of laying between island and mainland Mediterranean Blue Tits Parus caeruleus: phenotypic plasticity or genetic differences?
Authors: LAMBRECHTS MARCEL M. , DIAS PAULA C.
Published: April 2008

Blue tits Parus caeruleus breeding in deciduous or in evergreen woodlands on the mainland of Europe start to lay 3–4 weeks earlier than Blue Tits on the island of Corsica breeding in evergreen woodlands. A similar difference in average laying date between the two Blue Tit populations has been found in a relatively small sample of captive birds held in outdoor aviaries on the mainland. To provide data on the habitat contrast in Corsica for comparison with that on the mainland, a new study area was started in one of the few deciduous woodlands on Corsica. In addition, new data on laying dates of captive Blue Tits were gathered to increase the sample size of independent pairs in aviaries. This study shows that the habitat effect (deciduous ν evergreen woodland) on the average laying date of Blue Tits is relatively small in comparison with the geography effect (European mainland ν Corsica). The laying date differences between mainland and insular Blue Tits persisted whatever the type of habitat (deciduous, evergreen or outdoor aviaries on the mainland). The data support the hypothesis that the observed differences in the onset of laying between the mainland and insular Blue Tits were mainly influenced by genetic effects and relatively little by non‐genetic maternal effects of by genotype—environment interactions.
A less‐than‐annual breeding cycle in a pair of African Bat Hawks Machaeramphus alcinus
Authors: HARTLEY R. , HUSTLER K.
Published: April 2008

This cycle differs from the known situation in rural Bat Hawks which lay annually mainly during September and October. These probably take advantage of easily‐caught pregnant female bats in September/October in order to attain breeding condition, whereas fledgling Bat Hawks take advantage of recently independent but naive juvenile bats in January/February. The relative dearth of bats in rural areas outside this period may account for the regular annual breeding of Bat Hawks at the time of greatest prey availability.
Are Hazel Grouse Bonasa bonasia monogamous?
Authors: SWENSON JON E. , † DAVID A. BOAG
Published: April 2008

The apparently monogamous social organization of Hazel Grouse Bonasa bonasia previously had been inferred only from observations of unmarked birds. Using radio‐marked Hazel Grouse, we confirmed that the social organization during the breeding season was indeed monogamous, the pair being the social unit. The pair bond, however, appeared relatively weak, as birds were together only 37% of the time during the prelaying period. We could not document mating behaviour, but observations suggested that most males mated monogamously and that at least 37% of the females had an opportunity to mate polyandrously because of (1) the seemingly weak pair bond, (2) attentive neighbouring males, (3) larger territory size of unpaired males, (4) extensive movements of some unpaired males, (5) sharing of a female by two males and (6) a potentially male‐biased sex ratio.
A new species of Phylloscopus warbler from Hainan Island, China
Authors: OLSSON URBAN , ALSTRÖM PER , COLSTON PETER R.
Published: April 2008

Phylloscopus hainanus is a distinctive new species in the family Sylviidae. The species is endemic to Hainan Island, China, where it is restricted to tropical forest in mountains above 600 m. The most distinctive plumage features are the rather deep yellow underparts and the mainly white outer rectrices.
A new cockatoo (Psittaciformes: Cacatuidae) from the Tertiary of Riversleigh, northwestern Queensland, and an evaluation of rostral characters in the systematics of parrots
Authors: BOLES WALTER E.
Published: April 2008

The first Tertiary cockatoo or any psittaciform from Australia is recorded from an incomplete rostrum from the Riversleigh deposits of northwestern Queensland, Australia. It is placed in the extant genus Cacatua but cannot be diagnosed at the specific level. This cockatoo was probably similar in size to the modern C. roseicapilla, with a short, unspecialized crest and probably white plumage. The rostrum is useful in studies of the systematics of parrots. Rostral characters support some traditional subdivisions of the order, while suggesting that others warrant re‐examination.
The diet of young Lammergeiers Gypaetus barbatus in Corsica: its dependence on extensive grazing
Authors: THIBAULT JEAN‐CLAUDE , VIGNE JEAN‐DENIS , TORRE JOSÉ
Published: April 2008

This paper describes the diet of young Lammergeiers Gypaetus barbatus during the nesting period on the island of Corsica. From 1985 to 1990, food items were collected from 10 nests after the young had fledged. These nests were from five territories where the potential food supply was estimated using a range of ‘large mammal’ counts. Feathers, bones and isolated hooves were used to identify prey. For each nest, the minimal number of food portions was quantified, ignoring material that provided no food value. The diet consisted mainly of limb extremities of domestic ungulates (c. 36% by number of portions of sheep and goat; 33% of cattle, mostly calves). Pigs, both wild and domestic, yielded c. 16% of the items. Where present on the territory, mouflon occurred frequently in nests (c. 12% of items). Birds and small mammals were scarce in the diet. For three territories, samples varied less among years than among territories. There was a strong association between the diet of the young and the food available in the territories. We examined the possible links between known 20th century changes in stock rearing activities and the Corsican Lammergeier's diet.
Mass changes in migrating birds: the evidence for fat and protein storage re‐examined
Authors: LINDSTRÖM ÅKE , PIERSMA THEUNIS
Published: April 2008

The fact that one cannot kill a bird twice makes it very difficult to determine the relative contributions of fat and non‐fat components to increases in body mass before migratory flights in individual birds. Knowing the relative contributions of these components is of obvious energetic interest since fat yields about eight times as much energy as fat‐free muscle tissue. Several recent studies have failed to demonstrate convincingly, due to flaws in their analyses, that fat‐free mass in addition to fat is accumulated before long‐distance flights. We point out that regressions of fat or the non‐fat component on total body mass cannot yield reliable estimates of the composition of individual mass changes in view of inter‐individual variation in structural size, reserve levels or timing of storage. We suggest that studies over time of synchronous populations or marked individuals will give better answers. A re‐analysis of published data indicates the widespread existence of fat‐free tissue deposition during migration, whereas in some species fat alone explained the increase in total body mass. Larger species tend to incorporate a relatively higher proportion of non‐fat components when increasing in mass. However, the comparative data set is not yet of sufficient quality to allow general statements on why, and to what extent in different individuals and species, non‐fat tissue in addition to fat is deposited before take‐off on migratory flights.
The composition and foraging behaviour of mixed‐species flocks of forest‐living birds in Madagascar
Authors: EGUCHI KAZUHIRO , YAMAGISHI SATOSHI , RANDRIANASOLO VOARA
Published: April 2008

Mixed‐species flocks of forest living birds were investigated in a rainforest at Perinet/ Analamazaotra (Andasibe), Madagascar. Most insectivorous birds in the area participated in mixed‐species flocks. Flocks were composed of foliage gleaners, foliage‐branch gleaners, trunk gleaners and flycatchers. Species whose foraging techniques and foraging locations in vegetation were similar were different from each other in foraging heights. The nuclear species often occurred in small conspecific flocks in and out of mixed‐species flocks.
Commensal feeding associations between Yellow Wagtails Motacilla flava and cattle
Authors: Källander H.
Published: April 2008

Commensal ‘beating’ associations in which one party exploits prey disturbed by the other seem to be fairly common in terrestrial habitats (e.g. Dean and MacDonald 1981). Most such commensal relations appear to be opportunistic phenomena, rather than regularly occurring associations with possible fitness effects for the commensal, but few of them have been studied in detail. Exceptions are a few apparently very regular associations, for example those between birds and army ants (e.g. Willis 1966, Willis & Oniki 1978), between anis Crotophaga spp and cattle (Rand 1953, Smith 1971) and, especially, between Cattle Egrets Bubulcus ibis and large herbivorous mammals (for references, see Kushlan 1978). In the latter two cases, clear advantages in the form of higher food intake rates have been demonstrated for individuals foraging commensally (Rand 1953, Heatwole 1965, Smith 1971, Dinsmore 1973, Grubb 1976, Burger & Gochfeld 1982).
Diet and habitat use of the Dotterel Charadrius morinellus in Scotland
Authors: GALBRAITH H. , MURRAY S. , DUNCAN K. , SMITH R. , WHITFIELD D. P. , THOMPSON D. B. A.
Published: April 2008

The feeding ecology of Dotterel Charadrius morinellus adults and chicks was studied on three Scottish breeding areas. On the basis of 2324 prey items identified from 234 faeces, we show that (i) birds feed selectively and (ii) age‐related and seasonal differences in food selection occur.

The diet comprised mainly beetles (Coleoptera), sawflies (Symphyta) and the adults and larvae of Tipula montana. The faeces of adult Dotterel contained a high proportion of beetles, whereas chick faeces had more soft‐bodied prey. However, when T. montana adults emerged en masse (every second year) both adults and chicks took more tipulids. On one area, larval T. montana comprised much of the diet soon after the birds arrived on their breeding grounds and just before leaving in autumn. The preferred feeding habitats were flat or gently sloping Racomitrium lanuginosum or Juncus trifidus heaths or the transition zone between moss heath and montane bog. Dwarf‐shrub, grass‐dominated and single bog communities were avoided. The preferred feeding habitats were those in which pitfall trap catches of the main prey were highest. A close juxtaposition of montane bog and R. lanuginosum heaths met the feeding requirements of both chicks and adults, respectively. Recent changes in the breeding distribution of Dotterel in Britain may be related to de‐ terioration in feeding and breeding habitat due to overgrazing by sheep and greater habitat acidification.
The spring migration pattern of arctic birds in southwest Iceland, as recorded by radar
Authors: GUDMUNDSSON GUDMUNDUR A.
Published: April 2008

A surveillance radar in southwest Iceland was recorded by time‐lapse filming in order to monitor the migration pattern of birds departing from or passing Iceland on their way to high‐arctic breeding grounds in late May and early June 1988–1990. An overwhelming majority of the radar echoes from migrating bird flocks departed from Iceland but a few seemed to pass over from further south. Timing of movements and supplementary field observations indicated that mainly four species were involved, i.e. KnotCalidris canutus, TurnstoneArenaria interpres.SanderlingC. albaand Brent GooseBranta bernicla.Departures in late May from stopover sites in Iceland took place mainly in the afternoons, peaking between 1700 and 1900h in all 3 years. The departure intensity was lowest between 0100 and 1300h. Flight paths were generally straight, and the average track direction was towards the northwest (315°), suggesting that the majority of birds were heading for a transglacial migration across the Greenland icecap on their way to breeding grounds in northwest Greenland and northern Canada. Track directions varied with wind, although to a rather small degree, indicating partial drift or pseudodrift. More echoes were registered in easterly winds (tailwinds) and fewer in northerly winds than expected from random. Airspeeds were significantly slower than groundspeeds (average 17.0 and 18.7 m/s, respectively), showing that the birds more often than not benefited from tail wind assistance.
Does Chaffinch Fringilla coelebs song vary with the habitat in which it is sung?
Authors: WILLIAMS J. M. , SLATER P. J. B.
Published: April 2008

The acoustic adaptation hypothesis suggests that song learning in birds is advantageous because it enables song to become adapted to the habitat in which it is sung. A comparison was made among song types recorded from male Chaffinches Fringilla coelebs at a variety of sites in open scrub and in coniferous plantations, as well as in mature pine forest. Although some significant differences were found among habitats, these were few and there was no systematic relationship with features of the environment. This study does not therefore support the acoustic adaptation hypothesis.
Immediate and delayed effects of a gale in late spring on the breeding of the Shag Phalacrocorax aristotelis
Authors: AEBISCHER N. J.
Published: April 2008

At the beginning of May 1982, a westerly gale destroyed or damaged 49% of 761 Shag Phalacrocorax aristotelis nests on the exposed west side of the Isle of May, southeast Scotland; 518 nests on the sheltered east side acted as controls against which to assess subsequent effects of the gale on Shag reproduction and recruitment.

On sites affected by the gale, 90% of pairs rebuilt their nest and laid a second clutch, on average 18 days after the loss of the first one. First‐time breeders nested closer to the sea, suffered greater damage to their nests, and deserted their damaged nests more readily after the gale than did experienced ones; a quarter of potential recruits to the west side were deterred from breeding in that year.

By the end of the season, the number of chicks fledged per pair was 31% lower on the west side than on the east. The difference was caused partly by nest desertion, partly by greater hatching failure of full clutches in apparently undamaged nests and especially by lower fledging success of pairs that renested. Irrespective of breeding experience, delayed early breeders produced more chicks than late breeders nesting at the same time, showing that late breeders were of poorer intrinsic quality than early breeders. This was one reason for a seasonal decline in Shag productivity, although environmental factors also played a role.

During April‐July, gales like that of May 1982 occur on average once every 5 years on the Isle of May. Despite the disruption that they may cause to nesting Shags, the impact on the long‐term growth of the colony is small.
Intercolony movement and behaviour of immature Guillemots Uria aalge
Authors: HALLEY D. J. , HARRIS M. P.
Published: April 2008

A minimum of 61 Guillemots Uria aalge ringed as chicks at other colonies was recorded at the Isle of May between 1987 and 1991 (four prior to 1990, six in 1990, 51 in 1991). Two were adults and 59 were immatures. Most of the British and Irish colonies where many chicks had been ringed were represented. Higher proportions of birds ringed at colonies relatively close to the Isle of May were observed compared to birds ringed at more distant sites. Visitors ranged in age from 2 to 5 years, with single 10‐ and 14‐year‐olds. Relatively fewer 2‐ and 5‐ than 3‐ and 4‐year‐old birds were seen. Visiting birds were usually recorded once only, significantly less often than native immatures of the same age, except for 2‐year‐olds. The proportion of birds occupying sites on intertidal rocks as against sites in the colony appeared to be higher compared with native birds of the same age. Visiting birds formed a substantial proportion of the immature population. Ten immature birds from the Isle of May were recorded elsewhere. Four of these had been seen on the Isle of May previously, and four were seen there subsequently. A 6‐year‐old hatched at Sumburgh (c. 420 km by sea) bred at the Isle of May in 1992.
Differential responses of territorial Tawny Owls Strix aluco to the hooting of neighbours and strangers
Authors: GALEOTTI PAOLO , PAVAN GIANNI
Published: April 2008

Male Tawny Owls Strix aluco have individually distinct hooting calls. A classic play‐back experimental design was used to examine the differences in behavioural responses of a known owl to the hooting of a neighbour (familiar) compared with a stranger (unfamiliar) in order to test the hypothesis that such hooting variations are used in calibrating interactions between conspecifics. We tested 12 male Tawny Owls and their mates; the overall intensity of agonistic response was significantly higher when we stimulated birds using playbacks of strangers than when we did so with those of neighbours. The behaviour displayed and the type of voice used by Tawny Owls were stronger toward strange males. Moreover, on the occasions we broadcast a strange male hooting, the singing rate was higher while the latency was lower.
Cavity size, clutch‐size and the breeding ecology of Tree SwallowsTachycineta bicolor
Authors: RENDELL WALLACE B. , ROBERTSON RALEIGH J.
Published: April 2008

Previous studies provide evidence that cavity size influences clutch‐size and reproductive success in some hole‐nesting birds, because overcrowding in cavities may cause brood mortality due to trampling or hyperthermia. We tested this hypothesis with two experiments at nestbox populations of Tree SwallowsTachycineta bicolorin southeastern Ontario. Female Tree Swallows showed a preference for nesting in large boxes over small ones in the first experiment, and they laid significantly smaller clutches in small nestboxes during both experiments. Differences in clutch–size between large and small nestboxes could not be attributed to other factors known to influence clutch‐size in birds (e.g. parental quality, habitat quality, laying date). Reproductive success, however, did not differ between pairs using the two box types during either experiment, nor did it differ during within‐clutch‐size comparisons between box types. Some measures of nestling quality were significantly lower for broods in large boxes, but during most comparisons there were no differences. These results do not support the adaptive reason for why cavity size affects clutch‐size. We suggest that broods in our experiments did not experience the microhabitat conditions necessary to induce the expected differences in brood mortality.
Is the Starling Sturnus vulgaris a determinate layer?
Authors: MEIJER THEO
Published: April 2008

European Starlings Sturnus vulgaris have been said to be determinate layers, that is, they do not react to egg removals by laying extra eggs nor to egg additions by laying fewer eggs. Especially in species with a relatively small clutch‐size, such as the Starling, it is important to start these experiments early during the laying period to give the laying female the possibility of reacting to these additions and/or removals. I report here addition (n= 11 nests) and removal experiments (n= 35) early in laying period in a captive Starling colony. Additional information is presented about the development of incubation behaviour, a good predictor of clutch‐size. When three eggs were added to nests at 1500h on the first day of laying, females laid the normal number of eggs, and incubation behaviour developed regularly. Egg removals (one egg on three successive days) that started early in the laying period (at 1500h on the first day or at 0800h on the second day) arrested the development of incubation behaviour and resulted in the laying of extra eggs. Removals later in the laying period had no effect on the number of eggs laid nor on incubation behaviour. Following Kennedy's (1991) terminology, the starling is an addition‐determinate, and appears to be a removal‐indeterminate, layer.
Factors affecting nest defence in female Canada Geese Branta canadensis
Authors: SJÖBERG GÖRAN
Published: April 2008

The effect of various characteristics of Canada Goose Branta canadensis females and clutch size on their nest defence intensity during incubation was studied in the field during five nesting seasons. Nests were approached by a human, and the leaving distance was measured. Risk‐taking in post‐encounter behaviour was categorized at three levels. Nesting success was significantly associated with nest tenacity, a variable derived from leaving distance, but not with post‐encounter behaviour. Nest tenacity, as well as post‐encounter behaviour, differed significantly between individuals. Intensity of post‐encounter behaviour, but not nest tenacity, increased with increasing age of the female. Nest tenacity, standardized over the incubation period, increased with increasing clutch size, but post‐encounter behaviour intensity did not. None of the nest defence variables was correlated with the structural size of the female. Nest tenacity, but not post‐encounter behaviour intensity, increased during incubation. Nest tenacity did not differ between early and late breeders, but post‐encounter behaviour was more intense in late breeders. There was no evidence of positive reinforcement of nest defence through repeated visits. Nest defence did not differ between lakes, lake types or nest site types, nor was it affected by the distance to the nearest neighbouring nest. The results supported several of the predictions extracted from parental investment theory.