bluuebunny/crossref_metadata_2025 huggingface dataset:
Skuas on the Eurasian tundra; relative occurrence of species, ages and colour phases
Authors: KJELLÉN NILS
Published: April 2008

The breeding ranges of the three closely related skua species in the genus Stercorarius are highly sympatric on the Arctic tundra. During the Swedish‐Russian Tundra Ecology Expedition, 1994, the ages and colour phases of Pomarine Skuas Stercorarius pomarinus, Arctic Skuas Stercorarius parasiticus and Long‐tailed Skuas Stercorarius longicaudus were recorded at 15 sites along a transect across 140d̀ of longitude from the Kola Peninsula in the west to Wrangel Island in the east. An index of the lemming numbers was also measured. Pomarine Skua comprised 52% of the 1587 skuas seen, with 38% Long‐tailed Skua and 10% Arctic Skua. The Arctic Skua occurred at low densities all along the transect. The Pomarine Skua was most common at the northernmost sites in this lemming year. It was absent from all sites with low rodent densities but also from two more southerly sites with high lemming numbers. The Long‐tailed Skua showed a distribution sympatric with that of the Pomarine Skua but occurred at lower densities, and it also bred at the more southerly sites. No skuas in second‐year plumage were observed. Older subadult skuas were observed in increasing numbers with age. The proportion of subadults was markedly higher in the Pomarine Skua (10%) compared with the two other species. The proportion of dark Pomarine Skuas was about 8% all along the transect. In the Arctic Skua, there was an extremely marked shift from 64% dark birds on the Kola Peninsula to an almost complete dominance by the light phase in the rest of Arctic Russia. I suggest that dark skuas are more efficient kleptoparasites over the sea while the light phase is at an advantage hunting over the tundra.
The social system of the Pale Chanting Goshawk Melierax canorus; monogamy v polyandry and delayed dispersal
Authors: MALAN G. , CROWE T. M. , BIGGS R. , HERHOLDT J. J.
Published: April 2008

The social organization and reproductive strategy of the Pale Chanting Goshawk Melierax canorus were investigated in four southern African study areas. Territories supporting adults additional to the breeding pair were observed in two study areas. Within one of these areas, these additional adults were either non‐breeders staying in their natal territory but actively excluded from the nesting area during the breeding season or a male cobreeder participating fully in reproductive activities with the breeding pair. Polyandrous trios were, however, observed in only one vegetation type in this area, Broken Veld. The annual number of offspring fledged per group did not differ significantly between vegetation types nor between polyandrous trios and monogamous pairs within Broken Veld. Pale Chanting Goshawks lay predominantly two‐egg clutches. In 2 out of 5 years, breeding groups succeeded in laying, hatching and even fledging a second brood of young after successfully fledging their first brood. Double brooding occurred more frequently in Broken Veld and most frequently in polyandrous trios in this vegetation type. To accommodate their relatively long breeding cycle (>115 days) in this temperate study area with its limiting summer breeding period, double‐brooding Pale Chanting Goshawks laid the first clutch in midwinter and the second, on average, 24 days after the offspring from the first brood left the nest.
Differential habitat selection by immature and adult Grey Eagle‐buzzards Geranoaetus melanoleucus
Authors: BUSTAMANTE JAVIER , DONÉZAR JOSÉ ANTONIO , HIRALDO FERNANDO , CEBALLOS OLGA , TRAVAINI ALEJANDRO
Published: April 2008

During the 1992 breeding season, we studied the habitat selection, behaviour, aggressive interactions and diet of immature and adult Grey Eagle‐buzzards Geranoaetus melanoleucus in an area of the Argentinean Patagonia. Immature eagles selected areas rich in prey, had no preference for flat or rugged areas and did not avoid areas close to active nests or those used by adult eagles. The density of the European Hare Lepus europaeus was the best predictor of the distribution of immature eagles. Adult eagles preferred rugged to flat areas but were not significantly affected by prey distribution. Immature eagles used flapping flight more frequently than did adult eagles. Wing‐flapping frequency of immatures did not differ when flying over slopes or plains. In contrast, adults used a more economic flight with a lower wing‐flapping frequency than that of immatures, especially when flying over slopes. Adults, in contrast to immatures, tended to select slopes when flying over predominantly flat country. Only in 22% of the occasions when adult and immatures were seen together were immatures attacked by adults, a rate of aggressive encounters similar to that observed between immatures (32%). This similarity indicates that adults do not actively exclude immatures from certain areas. The main prey of both immature and adult eagles was the introduced European Hare followed by native rodents and birds. Immatures ate significantly more carrion and fewer birds than did adults. These observations suggest that differences in flight behaviour and in the flight silhouette between adult and immature eagles may be responsible for their different habitat selection in relation to topography. While immatures apparently cue on prey density for habitat selection, adults select areas that allow more economic foraging flights
Age‐assortative pairing in the Greater Flamingo Phoenicopterus ruber roseus
Authors: CÉZILLY FRANK , BOY VINCENT , TOURENQ CHRISTOPHE J. , JOHNSON ALAN R.
Published: April 2008

Among long‐lived bird species, the partners of breeding pairs are often of similar age. This pattern is largely influenced by little variation in the age at first breeding, linked with high survival rate and prolonged pair bonds. Contrary to other long‐lived colonial species, Greater Flamingos Phoenicopterus ruber roseus do not show mate fidelity over consecutive breeding seasons. We studied pairing patterns of Greater Flamingos breeding in the Camargue, southern France, between December 1989 and March 1992. In each year, significant correlations were observed between the ages of the male and the female in a pair. The pattern of age‐assortative mating was confirmed independently in each year by comparing the frequency distribution of age differences within pairs with the theoretical distribution derived from the age distribution of paired birds of known age in the population, assuming random pairing with respect to age. There was no evidence of a differential time of return each year to the colony with age. Analysis of display behaviour suggested that age‐as‐sortative mating in the Greater Flamingo results from a directional pairing preference for older and more experienced individuals. The present study provides direct evidence that age‐assortative mating can occur independently of mate fidelity.
One Norwegian territory of the Marsh Tit Parus palustris during 35 years
Authors: HAFTORN SVEIN
Published: April 2008

One Norwegian territory was occupied by successive pairs of Marsh Tits Parus palustris during 35 breeding seasons. Only ten males and seven females were involved. Each pair showed strict site fidelity and kept to the territory all year round. The pair bond lasted throughout life, and the duration varied from one to eight successive years. The number of successive mates varied for the males from one to two females and for the females from one to four males. Assuming that the birds were juveniles or 1 year old when ringed, they survived, on the average, 4.4 years. The oldest male survived for at least 10 years 4 months and the oldest female for 8 years 4 months. The mean survival rate of adults from one breeding season to the next was 75.8%, which is remarkably high when compared with the genera! findings in tits.
A comparative analysis of the diets of the Chough Pyrrhocorax pyrrhocorax and the Alpine Chough Pyrrhocorax graculus coexisting in the Alps
Authors: ROLANDO ANTONIO , LAIOLO PAOLA
Published: April 2008

The diets of the Chough Pyrrhocorax pyrrhocorax and the Alpine Chough Pyrrhocorax graculus coexisting in the western Italian Alps have been compared by faecal analyses. A total of 1581 fresh droppings (405 of the Chough and 1176 of the Alpine Chough) were collected in the pastures of the Rhêmes Valley, Aosta, Italy, from June to November 1992 and analysed in the laboratory, and a mean volume percentage for each item was calculated. Both species were omnivorous, including animal, vegetable and mineral dietary fractions. There was no overlap in the vegetable part of the diet since the Chough fed virtually exclusively on Yellow Gagea Gagea fistulosa bulbs (dug out from the soil), which were not taken at all by the Alpine Chough. Conversely, the Alpine Chough fed on berries and hips from September to November, but these were virtually ignored by the Chough. Even though animal items were collected by both species, their preferences were different. In June, Alpine Choughs largely collected cranefly (Tipula) larvae whilst Choughs mainly fed on Lepidoptera larvae. From July onward, Alpine Choughs mainly consumed grasshoppers while Choughs also collected Tipula pupae, Lepidoptera and fly (Bibionidae) larvae and beetles (Scarabaeidae and Staphylinidae). Interspecific morphological and behavioural differences may be partly responsible for the segregation observed. Chemical composition and caloric contents of the food items suggest that the balance between costs of collecting and benefits of consuming may also contribute to diet differentiation. Both species took a broad spectrum of food, and there was no clear indication that the different population densities of the two Choughs in the Alps were directly correlated with diet, even though some data suggest that during autumn the Alpine Chough might have a diet better adapted to the high mountain environment than the Chough.
Seabird associations in Pacific equatorial waters
Authors: RIBIC CHRISTINE A. , AINLEY DAVID G. , SPEAR LARRY B.
Published: April 2008

Seabirds were counted along the same cruise tracks in the eastern tropical Pacific (10°øN‐10°øS and 140°ø‐90°øW) each spring and autumn for 8 years, 1984–1991. During spring, three species groups were apparent among eight species seen in five or more years: (1) Leach's Storm‐petrel Oceanodroma leucorhoa and Wedge‐rumped Storm‐petrel Oceanodroma tethys, which feed on neuston by surface seizing; (2) Black‐winged Petrel Pterodroma nigripennis and White‐winged Petrel Pterodroma leucoptera, which feed on neuston and micronekton by surface seizing; (3) Juan Fernandez Petrel Pterodroma externa, Wedge‐tailed Shearwater Puffinus pacificus and Sooty Tern Sterna fuscata, which feed on micronekton driven to the surface by foraging tuna. During autumn, only one group was identified from the seven species seen in five or more years: Leach's Storm‐petrel associated with either Wedge‐rumped Storm‐petrel or Juan Fernandez Petrel and/or White‐winged Petrel. Annual variability in assemblage composition was more extreme in the autumn and thus was similar to variation in physical and biological factors linked to the El Niño‐Southern Oscillation cycle.
Surface tension prey transport in shorebirds: how widespread is it?
Authors: RUBEGA M. A.
Published: April 2008

Surface tension prey transport is a feeding mechanism employing the surface tension of water surrounding prey to transport prey from bill tip to mouth. Previously, it has been demonstrated only in the Red‐necked Phalarope Phalaropus lobatus. On the basis of a model of the bill morphology necessary for this method of prey transport, I suggest that many species of shorebird should be capable of surface tension feeding. Laboratory investigations of the feeding mechanics of Wilson's Phalarope Phalaropus tricolor, Western Sandpiper Calidris mauri and Least Sandpiper Calidris minutilla demonstrated that all three use surface tension transport of prey when feeding in water. I examined interspecific variation in the performance of this feeding mechanism with a high‐speed video system and a customized motion analysis system. Exploratory analyses indicated significant interspecific variation in distance the prey is transported per cycle of mandibular spreading, gape increase per unit transport, speed of transport, total number of cycles necessary to complete transport and total time to complete transport. The calidrid sandpipers also occasionally used other feeding mechanisms in conjunction with surface tension transport of prey. The discovery that these sandpipers, which normally obtain prey by probing, are capable of surface tension transport of prey implies that the capacity to employ this feeding mechanism may be widespread in the Scolopacidae and may have been a significant factor in the evolutionary radiation of phalaropes into aquatic environments.
Individuality of contact calls in the Greater Flamingo Phoenicopterus ruber and the problem of background noise in a colony
Authors: MATHEVON NICOLAS
Published: April 2008

Acoustic communication has great importance in social relationships and especially in individual recognition in the Greater Flamingo Phoenicopterus ruber. However, it is constrained by the noisy environment of the colony. I performed an analysis of both the temporal and frequency patterns of contact calls and showed that the use of both is essential for discrimination between individuals. I made a search for the acoustic parameters which are used by the flamingos. It appears that the call duration, the slow amplitude modulation, the spectrum bandwidth and the repartition of energy among harmonics exhibit individuality. Recognition between the birds must be based on a multiparametric analysis, taking into account both spectral and temporal features of the calls. Indeed, no single parameter was sufficient to discriminate between individual birds used in my research. In the noisy environment of the colony, the transmission of individuality in a message is improved by this multiparametric coding, which can be considered as an adaptation to these extreme acoustic conditions. Moreover, the study revealed numerous acoustic convergences with another colonial bird species, the Emperor Penguin Aptenodytes forsteri, and both species seemed to use the same method to encode individuality in their vocalizations.
Flight strategies of migrating raptors; a comparative study of interspecific variation in flight characteristics
Authors: SPAAR RETO
Published: April 2008

The comparison of flight styles and flight parameters of migrating raptors in Israel revealed the following. (1) Climbing rate in thermal circling did not differ between species, indicating that chiefly the strength of thermal updrafts determined the climbing rate and that morphological features were less relevant. (2) In interthermal gliding, air speed was positively and gliding angle negatively related to the species' average body mass. Heavier species glided faster and had smaller gliding angles. (3) In soaring and gliding flight, cross‐country speed relative to the air was positively related to the species' body mass; it was obviously the result of the gliding ability increasing with body mass. (4) Eagles and buzzards used soaring and gliding flight for more than 95% of the observation time. Additional soaring in a straight line whilst gliding was extensively used by the Steppe Eagle Aquila nipalensis, Lesser Spotted Eagle Aquila pomarina and Booted Eagle Hieraætus pennatus and even more frequently by the resident species, the Griffon Vulture Gyps fulvus and Shorttoed Eagle Circaetus gallicus. Smaller species, such as the Levant Sparrowhawk Accipiter brevipes, harriers (Circus sp.) and small falcons (Falco sp.). showed the highest proportion of flapping and gliding flight (9–33%). (5) In a comparison of the flight parameters and proportions of flight styles, a cluster analysis distinguished two main groups: The first consisted of Montagu's Harrier Circus pygargus, Pallid Harrier Circus macrourus, Levant Sparrowhawk and small falcons; their flight behaviour was characterized by both the high proportion of flapping and the low gliding performance. The second group comprised the typical soaring migrants: Steppe Eagle, Lesser Spotted Eagle, Booted Eagle, Steppe Buzzard Buteo buteo vulpinus, Honey Buzzard Pernis apivorus and Egyptian Vulture Neophron percnopterus, and they had very similar flight behaviour and were closely clustered. The Black Kite Milvus migrans and Marsh Harrier Circus aeruginosus were intermediate between typical soarers and flappers. The two resident species, Griffon Vulture and Short‐toed Eagle, were grouped separately from the soaring migrants.
Description of a new Cranioleuca spinetail from Bolivia and a “leapfrog pattern” of geographic variation in the genus
Authors: MAIJER SJOERD , FJELDÅ JON
Published: April 2008

A new species of spinetail (Furnariidae: Cranioleuca) is described from the dry Andean valleys of La Paz, Bolivia. Morphologically it is very similar to, yet distinguishable from, the Line‐cheeked Spinetail Cranioleuca antisiensis from northern Peru and southwestern Ecuador and the Pallid Spinetail Cranioleuca pallida from eastern Brazil. However, related forms which replace each other sharply in the intervening areas are much more different, giving a “leapfrog” pattern of geographic variation. We infer from this pattern that the geographically disjunct but similar‐looking forms are not particularly closely related to each other, and we suggest that all geographically adjacent and morphologically distinctive forms should receive equivalent taxonomic treatment.
Juvenile wing shape, wing moult and weight in the family Sylviidae
Authors: NORMAN S. C.
Published: April 2008

A study of 56 species of Sylviidae occurring in the western Palaearctic showed a significantly less extensive post‐juvenile moult in those species which incur longer migrations to winter quarters than in species that migrate short distances. Species with the more extensive post‐juvenile moult also undertook their first full moult in summer compared with the less extensive post‐juvenile moult in species with a full moult in the winter. In 11 species, young birds had shorter wings and lower body mass than adults. These differences produced significantly lower wing loadings in young birds compared with adults. Those species undertaking a full moult in the winter had significantly more pointed wings than species with their full moult in the summer. I suggest that this difference is the result of winter‐moulting species evolving from the probably basic strategy of a full post‐breeding (summer) moult. Some species, such as the Barred Warbler Sylvia nisoria, may be in the process of changing the full‐moult season from summer to winter.
A study of the seasonal booming activity of the Bittern Botaurus stellaris; what is the biological significance of the booms?
Authors: PUGLISI LUCA , CIMA ORNELLA , BALDACCINI N. EMILIO
Published: April 2008

Booming activity was studied in five focal male Bitterns Botaurus stellaris at two different marshlands of central Italy. For each individual, the length of the booming season, the seasonal and evening pattern of booming rate, the seasonal pattern of booming effort and some characteristics of the boom “trains” (sequences of calls) were studied. The lack of a common pattern of vocalization was noted, while the booming males showed individual patterns with regard to all the above characteristics. The length of the booming season and the booming effort differed at the two sites. While one bird was unique with respect to the quality of the vocalizations, a common characteristic of the remaining four focal birds was a marked increase or resurgence in booming activity in a period of the breeding season which coincided with the presence of the nestlings. Mainly on the basis of this particular seasonal vocalization pattern, we discuss the possible meaning of the booming activity of the male Bittern. One function of the booming activity suggested is the defence of a feeding territory, where the females of the booming male can find food to feed the nestlings. For the male, this appears to be his only contribution to the rearing of the offspring.
On the skewed sex ratio of the Kakapo Strigops habroptilus: sexual and natural selection in opposition?
Authors: TREWICK STEVEN A.
Published: April 2008

The Kakapo Strigops habroptilus is unique amongst parrots in many respects, not least its use of a lek breeding system. Since Merton et al. first described the phenomenon, little new information has come to light, chiefly as a result of the extreme rarity of Kakapo. Observation of an extreme sex ratio skew in favour of males has received little attention and has been considered spurious. I used subfossil material to examine the nature of the sex ratio prior to the arrival in New Zealand of humans and demonstrated that a sex bias in favour of males in the order of 2:1 existed at that time. Although apparently untenable on traditional theoretical grounds, this extreme skew has been persistent and has resulted from the interaction of sexual and natural selection on dimorphic male and female Kakapo. Relatively small, sole caring females may suffer the consequences of parental investment as a result of demands made by offspring over an extended rearing period. In particular, larger male chicks may exert a greater cost on the parent bird than do female siblings. Additionally, brood reduction in certain circumstances may favour the survival of dominant male siblings.
Genetic differences among mainland and insular forms of the Citril Finch Serinus citrinella
Authors: PASQUET ERIC , THIBAULT JEAN‐CLAUDE
Published: April 2008

The Citril Finch Serinus citrinella breeds in several mountains of central and southern Europe and on Corsica, Sardinia and Tuscany islands. Several studies have emphasized differences in phenotype and vocalization, and some authors consider mainland and insular forms to be two distinct species. A genetic approach based on the sequences of a mitochondrial DNA fragment was used to estimate genetic distance separating several populations. Individuals from the Alps and the Pyrenees belong to one group and the individuals from Corsica to the second. These results, discussed together with data on ecology, biometrics and vocalization, suggest keeping only one polytypic species which includes two distinct forms.
Seabirds attending bottom long‐line fishing off southeastern Brazil
Authors: OLMOS FÁBIO
Published: April 2008

Flocks of seabirds attending commercial bottom long‐line fishing operations on the coastal shelf off southeastern Brazil show a greater species diversity during the summer than the winter (16 v 9 species), although the number of birds per flock tended to be greater during the cold season. During the summer, the Spectacled Petrel Procellaria aequinoctialis conspi‐cillata was the commonest species, followed by the Great Shearwater Puffinus gravis, Cory's Shearwater Calonectris diomedea, skuas Stercorarius spp. and the Yellow‐nosed AlbatrossDiomedea chlororhynchus. During the winter, the White‐chinned Petrel Procellaria aequin‐octialis, Yellow‐nosed Albatross and Black‐browed Albatross Diomedea melanophrys were jointly the commonest species. Marked differences in the relative abundance of species were observed between the different sampling periods, probably because of migratory movements but also because of seasonal shifts of the sea currents and the influence of cold fronts. Waters off southeastern Brazil are important feeding areas for some seabird populations nesting in the Tristan da Cunha and Gough group, especially for nonbreeding Spectacled Petrels and post‐breeding Yellow‐nosed Albatrosses.
Survival of adult Great Tits Parus major in relation to sex and habitat; a comparison of urban and rural populations
Authors: HORAK PEETER , LEBRETON JEAN‐DOMINIQUE
Published: April 2008

Capture‐recapture data were obtained for two populations of Great Tits Parus major in southeast Estonia, one rural, the other urban. These data were used to estimate and compare survival probabilities between sexes and populations using capture‐recapture statistical models. As is generally assumed, urban birds survived better than rural ones. Females survived better than males, and the survival probabilities varied over time. The three sources of variation considered (sex, habitat and time) had additive effects on survival probability on a logit scale. The estimated annual survival probabilities varied from 0.19 to 0.70. The averages over time ranged from 0.26 to 0.47 and were generally lower than published estimates from other populations. The proportion of yearling breeders was higher among females than among males, contrary to what could have been deduced from survival patterns, and is possibly a consequence of complex recruitment mechanisms.
Distribution and reproductive success of the Pied Flycatcher Ficedula hypoleuca in relation to forest patch size and vegetation characteristics; the effect of scale
Authors: HUHTA ESA , JOKIMAKP JUKKA , RAHKO PEKKA
Published: April 2008

We studied habitat choice, distribution and reproductive success in the Pied Flycatcher Ficedula hypoleuca in relation to the spatial structure of a fragmented forest area. Two hierarchical levels of forest habitat structure were used: (1) forest patch size (macrohabitat) and (2) vegetative structure within forest patches (microhabitat). In spring, both males and females settled preferentially in large and medium‐sized forest stands (>1 ha) where breeding density was also higher than in small stands (<1 ha). Stands <5 ha were occupied later, and the proportion of unpaired males was higher there than in large stands (>5 ha). The known age distributions of breeding birds and breeding success were independent of forest patch size. Nest predation rate was not associated with stand size or nest distance from the forest edge. The preference of breeding birds for large forest patches was presumably related to the higher amount of resources (nest sites, mates, food) a large patch can offer for reproduction compared with a small patch. At the microhabitat level, territories of old males were characterized by relatively more deciduous trees that contained more invertebrate food than coniferous tree‐dominated territories of yearling males. The reproductive success of old males, as measured by the number of fledged young per male, was higher than that of yearling males. This suggests that the larger body size and blacker plumage of old males possibly contributed to male dominance and that old males excluded younger males from preferred habitats through territorial behaviour. Our results suggest that habitat choice of the Pied Flycatcher was affected by both micro‐ and macrohabitat. On the basis of settlement pattern, density and reproductive success, the distribution of Pied Flycatchers across forest stands of different sizes followed the ideal‐free distribution model, whereas at the microhabitat level, age‐related unequal distribution of males followed the ideal‐despotic model of Fretwell and Lucas.
Effects of nest‐site availability and distribution on density‐dependent clutch size and laying date in the Chough Pyrrhocorax pyrrhocorax
Authors: BLANCO GUILLERMO , FARGALLO JUAN A. , CUEVAS JESÚS A. , TELLA JOSÉ L.
Published: April 2008

We compared the breeding phenology and clutch size of Choughs Pyrrhocorax pyrrhocorax in three Spanish areas that differed in feeding habitat, breeding environmental conditions and the distribution and availability of different nesting sites (cliffs or artefacts). The variation in the timing of laying seemed to be related to differences in climatic conditions determined by the altitude. The variation in clutch size was associated with the different use that Choughs made of the feeding areas because of the contrasting availability and distribution of their nesting sites. Within southeastern Madrid, clutch size of the Chough decreased and its variance increased at high nest densities on cliff sites, suggesting that density dependence in fecundity arises from habitat heterogeneity rather than by interference. At high densities, individuals, territories, nest sites or a combination of these may differ in quality, thus promoting differences and increasing the variance in the initial investment of reproductive effort. The syncronization of the onset of laying at increased breeding densities suggests that social influences arising from communal foraging or avoidance of predation by early warning and predator swamping may be acting also. We suggest that nest‐site availability and distribution have a major influence on the social organization of Choughs through their breeding and foraging strategies.
Identifying predators at nests of small birds in a New Zealand forest
Authors: BROWN K. P. , MOLLER H. , INNES J. , JANSEN P.
Published: April 2008

Time‐lapse video equipment was used to film continuously at nests of two small passerines, the New Zealand Robin Petroica australis and the Tomtit Petroica macrocephala, in an indigenous broadleaf/hardwood forest in central North Island, New Zealand. The nests were illuminated with infrared light to allow night‐time observations of predator and parent bird behaviour, and signs left at nests were linked to predator identity. Introduced Ship Rats Rattus rattus and the small native owl or Ruru Ninox novaeseelandiae were filmed preying on eggs or chicks on 12 occasions, and Ship Rats scavenged on eggs on two occasions. Parent birds sometimes altered the signs left at nests after predation, which confused identification of the predator, while Ship Rat scavenger and predator signs were indistinguishable. This suggests that attempts to identify predators from nest signs could be misleading and potentially a widespread problem. Time‐lapse video filming with infrared illumination is potentially the least biased method of identifying predators, but it is expensive and so is best used in conjunction with simpler methods. This study found no evidence that filming altered predation rates or that the predators or parent birds reacted strongly to the camera or lights, so we believe that filming is a valuable and safe technique to guide management for the recovery of critically endangered species that are threatened by predators.
The function of flight formations in Greylag Geese Anser anser; energy saving or orientation?
Authors: SPEAKMAN J. R. , BANKS D.
Published: April 2008

Twenty five formations of Greylag Geese Anser anser were photographed from immediately below to eliminate perspective distortion, and the lateral and longitudinal displacements of the birds relative to each other were measured. We scaled the photographs and used measurements of bill to tail and wing span made on 15 freshly shot birds to convert the lateral displacements to wing‐tip spacings. The birds flew on average with an overlap of their wing tips (median =17 cm) which corresponded very closely with the overlap expected (16 cm) from an aerodynamic model which predicted the position which maximized energy savings. However, the variation in positions was large, and only 17% of birds actually flew in the optimum range. The mean saving in induced power averaged across the distribution of positions was 26.5%, and the contribution to total flight costs was a reduction of 4.5–9%. This saving was greater than we found previously in the Pink‐footed Goose Anser brachyrhynchus. There was no correlation between position in the skein and longitudinal displacement, as would be anticipated if the birds were equalizing the savings across the skein. This does not mean costs were not equalized because other mechanisms are possible. There was no correlation between depth and wing tip spacing which does not support the orientation/communication hypothesis. Body size and thus flight costs may be a factor influencing the function of formation flights.
Geographic variation of the winter diet of the Red Kite Milvus milvus in the Iberian Peninsula
Authors: GARCÍA J. T. , VIÑUELA J. , SUNYER C.
Published: April 2008

This paper presents data on the winter diet of the Red Kite Milvus milvus in the Iberian Peninsula. The diet composition and its relationship with food abundance and habitat characteristics were studied in two areas (northern and southern plateaux) with different food availability and habitat composition. Red Kites showed a clear difference in diet between the two plateaux, with a higher consumption of carrion on the northern plateau and of game species on the southern plateau. Common Voles Microtus arvalis, despite being a very abundant prey on the northern plateau, did not appear in the diet in high numbers, but their frequency was related to the proportion of land occupied by nonirrigated (cereal) crops. High frequencies of “small” carrion (e.g. farmed Rabbits Oryctolagus cuniculus, poultry Gallus sp.) in the diet were correlated with a decrease in the trophic diversity which suggested an active choice of the food, at least in years with low vole densities. We suggest that the use of carrion is influenced not only by its abundance but by its availability to Red Kites. Refuse tips and muladares (dumps for dead livestock) and their management during the winter are important for the conservation of the species.
Individual quality and reproductive performance in the Grey‐headed Albatross Diomedea chrysostoma
Authors: COBLEY N. D. , CROXALL J. P. , PRINCE P. A.
Published: April 2008

The reproductive performances of Grey‐headed Albatrosses Diomedea chrysostoma with a previous record (≤5 years) of consistent success (≤70% chicks fledged from eggs laid—“top” birds) or failure (≤ 70% of attempts failed—“bottom” birds) were compared during 1993 ‐1995. In 1995, top birds arrived back at the colony significantly earlier, had significantly shorter first and second incubation shifts and hatched larger chicks which grew significantly faster than bottom birds. In 1994, top birds also had larger hatchlings with higher rates of growth than bottom birds. In 1994, top birds had significantly higher hatching, fledging and therefore overall breeding success than bottom birds; very similar trends were evident in 1993 and 1995. Chick‐rearing success and all indices of chick growth suggested that food availability was high in 1995 (and 1993) and low in 1994. Therefore the superior performance of top birds was maintained in years of very different conditions, with the chick‐rearing period particularly critical. A simple model (using published demographic parameters for Grey‐headed Albatrosses on South Georgia) suggests that top birds would produce 2.5 more chicks over their lifetime than bottom birds. With the currently declining population numbers, the relative contribution of top birds to the next generation may be even greater than this.
Cost reduction in the cold: heat generated by terrestrial locomotion partly substitutes for thermoregulation costs in Knot Calidris canutus
Authors: BRUINZEEL LEO W. , PIERSMA THEUNIS
Published: April 2008

To test whether heat generated during locomotion substitutes for the thermoregulation cost, oxygen consumption of four post‐absorptive temperate‐wintering Knot Calidris canutus was measured at air temperatures of 25d̀C (thermoneutral) and 10d̀C (c. 10d̀ below the lower critical temperature) when the birds were at rest at night and during running on a treadmill. After allowing for body mass, the thermoregulation cost at 10d̀C was significantly lower in active birds compared with birds at rest. At rest, the birds spent, on average, 0.50 watt (W; range, 0.47‐0.57 W) on thermoregulation. During exercise, this cost factor averaged 0.33 W (range, 0.25‐0.42 W). The average difference in thermoregulation cost was 35% (ranging from 26% to 49% between individuals) and provides an estimate of the amount of substituted heat. A review of nine studies, all restricted to small birds, showed that substitution is a widespread phenomenon. The consequences of such partial substitution for the annual energetics of Knot wintering in the temperate Wadden Sea v tropical west Africa are examined. Compared with a previous additive model, the model which includes substitution (i.e. the use of heat produced during activity) reduces the differences in maintenance metabolism between the two wintering strategies by 17%, from 1.19 W to 0.99 W.
Competition and coexistence of the European Bee‐eater Merops apiaster and the Blue‐cheeked Bee‐eater Merops persicus in Asia
Authors: KOSSENKO S. M. , FRY C. H.
Published: April 2008

Studies were conducted over a 10‐year period on the supposedly similar European Bee‐eater Merops apiaster and Blue‐cheeked Bee‐eater Merops persicus breeding in mixed and separate colonies in four Asiatic countries. In spring, M. persicus arrived a few days later and laid up to 2 weeks later than M. apiaster. Spatial distributions of the two species were positively associated. They were sympatric and syntopic: more than half of the local breeding ranges overlapped, and many birds bred within sight and sound of the congener. Intraspecific conflict was frequent, but in mixed colonies interspecific conflict was rare. Most M. apiaster nest burrows were dug into cliffs and most M. persicus ones into level ground, but dense mixed colonies occurred only in cliffs. Burrow architecture differed specifically. Diets were qualitatively similar at insect family level but different at the species level, partly because of local variation in availability and partly because of distinct preferences of M. apiaster for small beetles, ants and termites and of M. persicus for large dragonflies and cicadas. Merops persicus was less specialized than M. apiaster and had an airborne insect prey spectrum nearly twice as broad. Diets were more alike where the two birds foraged together than where they foraged separately. There was a high incidence of egg and nestling loss by predation and starvation.

We speculate that each species may prove to breed more successfully in mixed than in monospecific colonies. We propose that the two bee‐eaters do not compete for nest sites but may compete for food and coexist unaggressively by trading off food competition against improved breeding success in mixed colonies.
The effects of prey size on diet differentiation of seven passerine species at two spring stopover sites
Authors: MARCHETTI CHIARA , LOCATELLI DARIA PATRIZIA , NOORDWIJK ARIE J. VAN , BALDACCINI NATALE EMILIO
Published: April 2008

Prey size was evaluated for seven passerine trans‐Saharan migrant species at two spring stopover sites in Sardinia, Italy. The species considered were Pied Flycatcher Ficedula hypoleuca, Spotted Flycatcher Muscicapa striata, Redstart Phoenicurus phoenicurus, Garden Warbler Sylvia borin, Whitethroat Sylvia communis, Willow Warbler Phylloscopus trochilus and Wood Warbler Phylloscopus sibilatrix. The analysis was made for three prominent prey types: beetles (Coleoptera), ants (Hymenoptera: Formicidae) and “flying prey” (wasps and bees [Hymenoptera, excluding ants] and flies, Diptera, pooled), The prey size distribution in the diets of some species was very similar to that caught in our insect traps, showing that our estimates of availability are, at least partially, relevant. On the whole, diets deviated from food available in a species consistent way. The size distributions of “flying prey” differed between the two sites but were almost constant in the birds' diets. In contrast, size distributions of available beetles and ants at the sites were similar but were different in the birds' diets. Different feeding behaviour of the birds, in terms of physiological constraints during migratory stopovers, is discussed. Paired species comparisons show that the diets of most species differ significantly in the distribution of the size classes of at least some prey types. The conclusions drawn from the comparisons of the size distributions of all prey items collected from a bird species in one season are very similar to the conclusions drawn from comparisons based on the presence/absence of a size class per faecal sample. We compared the similarities of diet with and without using information on prey size. With the exception of the Pied Flycatcher and the Redstart at one of the study sites, size information did not add to diet segregation. Certain size classes within prey types tended to be common in the diet of these migrant passerines. However, specialization on certain size classes within broad taxonomic categories was not evident.
Photoperiodic control of the termination of breeding and the induction ofmoult in House Sparrows Passer domesticus
Authors: DAWSON A.
Published: April 2008

Two photoperiodic mechanisms controlling gonadal regression in birds have been identified: absolute photorefractoriness, typical of species with short breeding seasons, where gonadal regression occurs spontaneously during long days, and relative photorefractoriness, where a decrease in daylength is required to induce regression. An experiment was designed to test whether these simply represent extremes of one underlying mechanism. Three groups of male House Sparrows Passer domesticus were transferred from a short photoperiod, 8 h of light: 16 h of darkness per day (8L:16D) to long photoperiods of either 18L:6D, 16L:8D or 13L:11D. Gonadal maturation rates were similar in all three groups; gonadal regression and moult began latest in the 13L:11D group. Four additional groups of sparrows were transferred from 8L:16D to 18L:6D and then transferred to either 13L: 11D or 16L:8D prior to, or shortly after, the onset of gonadal regression. The decrease in daylength prior to regression had no effect on the timing of regression but did advance the onset of moult. Decrease in daylength after the onset of regression increased the rate of regression and the rate of moult. Because a decrease in daylength did not affect the timing of regression, the data do not support the hypothesis that absolute and relative photorefractoriness represent extremes of a single underlying photoperiodic control mechanism. The adaptive significance of the effects of decreasing daylength on the rate of regression and moult is discussed.
Successful breeding at one year of age by Red Kites Milvus milvus in southern England
Authors: EVANS IAN M. , CORDERO PEDRO J. , PARKIN DAVID T.
Published: April 2008

This paper presents the first data on individually tagged male and female Red Kites Milvus milvus breeding at 1 year old and is validated by genetic fingerprinting. The data were collected during 1989 to 1994 when Red Kite nestlings were translocated to, and released in, southern England as part of a re‐establishment project. A total of 23 1‐year‐old Red Kites attempted to breed in southern England from 1991 to 1994, of which three pairs, each composed of at least one yearling bird, reared five young. We conclude that habitat quality is ultimately the main influence that determines whether Red Kites can breed and how well they breed. However, individual experience, climate and competition with other Red Kites for nesting territories probably influence the age at which an individual can breed in a particular habitat.
Seasonal pattern in age, sex and body condition of Barn Owls Tyto alba killed on motorways
Authors: MASSEMIN SYLVIE , MAHO YVON LE , HANDRICH YVES
Published: April 2008

The Barn Owl Tyto alba was the most common owl killed on motorways in northeastern France. The possible causes of this mortality and the age, sex and body condition of the road‐killed birds in 1991–1994 have been investigated. The number of birds killed on roads was highest in the period from early autumn to late winter, i.e. during the non‐breeding period, and showed a pattern similar to that of the temporal difference between sunset, which varies with day length, and peak of traffic, the occurrence of which is constant throughout the year. An autumnal mortality peak, concomitant with the post‐fledging dispersal, was mainly of immature birds, especially females. A second mortality peak in late winter was composed mainly of mature birds, with an equal proportion of males and females. From autumn to winter, there was no significant change in body mass in the different age and sex categories of birds killed on roads, except for mature males which had a significantly lower body mass in winter. From early autumn to late winter, the mean body mass of immature owls killed on motorways did not differ significantly from that of captive immatures fed ad libitum. This suggests that the immature birds were in good body condition. In contrast, the body mass of road‐killed mature females was significantly lower than that of captive mature females over the same time periods. In mature males in late winter, a drop in body mass in both road‐killed and captive birds suggests an endogenous seasonal phenomenon. Except for mature females, Barn Owls killed on roads in 1991–1994 were in good body condition. This does not support the idea that only birds in poor body condition were killed. We conclude that the mortality of Barn Owls on motorways in autumn and winter was probably related to the concomitance between the peak of traffic and the onset of hunting activity and the large number and dispersal of immature individuals during the same period.
Water depth selection, daily feeding routines and diets of waterbirds in coastal lagoons in Ghana
Authors: NTIAMOA‐BAIDU YAA , PIERSMA THEUNIS , WIERSMA POPKO , POOT MARTIN , BATTLEY PHIL , GORDON CHRIS
Published: April 2008

Water depth requirements, diet, feeding styles and diurnal activity patterns are described for waterbirds using two brackish water lagoon systems in coastal Ghana, the Songor and Keta Lagoons. We project the habitat and activity data on a guild structure defined on the basis of individual feeding style and the sensory mechanism used to detect food. A total of 3199 flocks containing 118,648 individuals of 36 different waterbird species were examined during October‐November 1994. Feeding habitats varied from dry mudflats to wet mud and shallow water of not more than 20 cm. The depth of water selected by waterbirds for foraging (but not for roosting) was correlated with tarsus length. Foraging birds exhibited a wide range of feeding styles using visual and/or tactile means for detecting prey: pecking, probing, stabbing, sweeping and ploughing, sometimes feeding singly, communally or socially in loose or dense flocks. Prey items taken ranged from seeds of Widgeongrass Ruppia maritima to invertebrates (mainly polychaetes, molluscs and crabs) and fish, mainly juvenile Tilapia. The daytime was spent on two main activities, feeding and roosting, with a small fraction of the time (average of 10% for 25 species) spent on comfort activities. The waterbirds exhibited either a circadian (most waders, except Common Sandpipers Actitis hypoleucos and Turnstones Arenaria interpres) or a diurnal foraging activity pattern (herons and terns), with no purely nocturnal species. Some species fed throughout the day, others showed peak foraging at various times of the day. The proportion of time spent foraging was related to guild (highest in visual and tactile surfaceforaging waders) and was negatively correlated with the size of the species. We conclude that the observed patterns in the use of the 24‐h day by waterbirds for foraging are not species specific but vary depending on conditions on the feeding grounds. Nocturnal foraging is a normal and a regular strategy used by waterbirds to obtain enough food to fulfill their energetic requirements, so that irrespective of the sensory mechanism used to detect prey and the conditions prevailing on the feeding grounds, waterbirds forage day and night as dictated by their energetic needs. Water depth appears to be the key environmental factor controlling the availability of food for the waterbirds in the Ghanaian lagoons.