bluuebunny/crossref_metadata_2025 huggingface dataset:
Social rank and antipredator behaviour of Willow Tits Parus montanus in winter flocks
Authors: HOGSTAD OLAV
Published: April 2008

Field experiments on three free‐ranging Willow Tit winter flocks, each consisting of one adult pair and two male and two female juveniles (first‐year birds), were performed to examine whether preferences for feeding site and antipredator behaviour are related to social rank. The dominance structure was the same in all flocks; adult male > juvenile male 1 > juvenile male 2 > adult female > juvenile female 1 > juvenile female 2.

The proportion of time spent scanning for predators was positively correlated with distance from cover, and adults scanned relatively more than juveniles at the same controlled distance from cover, especially in the afternoon. Given a choice between feeders placed 1 m, 3 m, 5 m, 10 m and 20 m from the forest edge, the tits preferred feeders close to cover. Low‐ranking individuals used feeders farther from cover indicating that higher ranked tits prevented them from using the feeders close to cover by means of social dominance. When only the 10m and 20 m feeders were baited, only low‐ranked juveniles visited the feeders, subordinate females slightly more than males. The subordinate juveniles increased their use of exposed feeders at low ambient temperature, suggesting that they are prepared to take greater risks during cold periods.

The sequence of return to a feeder, after a life‐like stuffed predator model mounted 1 m from a feeder opening was removed, was positively correlated with dominance status, revealing that subordinates take the greatest predation risks.
Distribution and movements of Barrow's Goldeneye Bucephala islandica young in relation to food
Authors: EINARSSON ÁRNI
Published: April 2008

Barrow's Goldeneye females with broods in the Lake Mývatn district, Iceland, concentrated in a small area in the lake's outlet where the density of blackfly Simulium vittatum larvae, the principal food of the young, was highest. A downstream migration of broods took place as predicted from the growth pattern and emergence of blackflies in the river.
The diet of the King Penguin Aptenodytes patagonicus at Macquarie Island
Authors: HINDELL MARK A.
Published: April 2008

The diet of King Penguins Aptenodytes patagonicus at Macquarie Island was studied between November 1984 and November 1985 based on stomach flushed samples (obtaining 93% of the total stomach content) from ten birds each month. The mean stomach content mass of the 118 samples was 923 0 g. Percentage by number, percentage by weight and dietary coefficient analysis all showed the main prey of the penguins to be myctophid lantern fish of the species Electrona carlsbergi and Krefftichthys anderssoni. Juvenile fish of both species were eaten from December to July, and adults in August and September. Cephalopods were relatively unimportant in contrast to previous indications. The amount of food brought ashore and the composition of the diet varied over the year, with K. anderssoni the dominant food in all but the winter months when E. carlsbergi replaced it as the principal food item.
Prerequisites for recruitment of Kittiwakes Rissa tridactyla
Authors: PORTER J. M.
Published: April 2008

Observations at the North Shields Kittiwake colony between 1982 and 1984 showed over 100 potential recruits (birds of breeding age) associated with the colony, only about 40% of which were actually recruited. In addition, there were younger birds which visited the colony. The origins, age structure and intercolony movements of members of the pool of prospectors have been examined. Porter & Coulson (1987) demonstrated that recruits are heavier than prospectors, implying that they are in better body condition. Three further prerequisites for breeding in Kittiwakes are recognized: the age of recruits is at least three years; all birds which recruit are present at the colony at least one year prior to breeding; and recruits show a high degree of attachment to colony as illustrated by their colony and nest site tenacity, attendance and early arrival. The results suggest that there is considerable selection of individuals at the time of recruitment; the mechanism for this has yet to be examined.
Adoption behaviour by gulls: a new hypothesis
Authors: HÉBERT PERCY N.
Published: April 2008

It appears that chicks are selected to run away and seek adoption in a foster‐family when the level of investment they receive falls below a certain threshold. Predictions based on this hypothesis are in agreement with the available evidence in the literature.
Assimilation efficiency and growth of nestling insectivores
Authors: BRYANT D. M. , BRYANT V. M. T.
Published: April 2008

The efficiency of energy assimilation by Pacific Swallows Hirundo tahitica and Blue‐throated Bee‐eaters Merops viridis was measured in captive nestlings fed on their natural diets. Assimilation efficiency (AE) was 68% in Pacific Swallows, similar to published values for altricial nestlings, including other hirundines. AE was unusually low in Blue‐throated Bee‐eaters, conforming to results with the European Bee‐eater Merops apiaster, at around 57%. As expected, nestling growth was positively correlated with daily metabolized energy. Estimates of daily metabolized energy for captive reared nestlings, closely resembled estimates obtained for wild youngsters in an earlier study using different methods.
Differential predation of eggs in clutches of Glaucous‐winged Gulls Larus glaucescens
Authors: VERBEEK NICOLAAS A. M.
Published: April 2008

Differential predation of eggs of Glaucous‐winged Gulls Larus glaucescens was studied on Mitlenatch Island, British Columbia. The predation of single eggs from 3‐egg clutches by conspecifics and Northwestern Crows Corvus caurinus was recorded to assess whether the predators selected eggs at random or showed a preference for a specific egg in the laying sequence. It was found that small and light‐coloured eggs, characteristically the last‐laid egg in the clutch, were taken significantly more often than the other two eggs in the clutch. As chicks derived from this third egg are least likely to fledge because of their small size and the effects of asynchronous hatching, the lightness of the third egg is adaptive in that it helps to focus attention on the small egg.
An aid to the identification of arthropod fragments in the faeces of gamebird chicks (Galliformes)
Authors: MOREBY S. J.
Published: April 2008

A method is described for the identification of arthropod fragments in the faeces of gamebird chicks. The method of collection and preparation of faecal samples and the identification of commonly occurring arthropod parts is described. The use of diagnostic parts, specific to certain groups, enables the method to be used quantitatively as well as qualitatively. Photographs of the major diagnostic features are provided.
Wax digestion by Black‐throated Honey‐guides Indicator indicator
Authors: DIAMOND A. W. , PLACE A. R.
Published: April 2008

The honey‐guides (Indicatoridae) are brood parasites and specialist feeders on wax; the larger species obtain wax from bees' nests and the smaller ones from scale‐insects or fruit (Friedmann 1955, Diamond 1985). The ability to digest beeswax has been demonstrated experimentally in only one bird species, the Lesser Honey‐guide Indicator minor (Friedmann & Kern 1956a). Here we describe an experiment confirming the same ability in the Black‐throated or Greater Honey‐guide, 1.indicator, and discuss reasons for questioning Friedmann and Kern's claim that wax digestion in honey‐guides need be accomplished hy symbiotic microorganisms.
Geographic variation in nest‐defence behaviour of the Red‐tailed Hawk Buteo jamaicensis
Authors: KNIGHT RICHARD L. , ANDERSEN DAVID E. , BECHARD MARC J. , MARR N. VERNE
Published: April 2008

A close fit was found between the number of years since European settlement and the call and dive‐rates of Red‐tailed Hawks. Call‐rates were highest in the most recently settled sites.
Mating system and mate choice of Tengmalm's Owls Aegolius funereus
Authors: KORPIMÄKI ERKKI
Published: April 2008

The mating system and mate choice of Tengmalm's Owls were studied in relation to population fluctuations of the staple food (voles) for seven years in western Finland. Three age classes of owls were differentiated: first‐year, second‐year and older owls. Despite a surplus of males, 11 % of them showed simultaneous bigyny in peak vole years. The mean distance between primary and secondary nests was 1158 m, and usually there was a free nest‐box between the two nests. Because primary nests produced more fledglings than secondary ones and secondary nests produced fewer fledglings than simultaneous or even eight‐days‐later monogamous nests, this bigyny could be best explained by the ‘deception’ hypothesis.

In successive biandry, females deserted their first brood when young were still in the nest, thereby transferring the burden of raising the young to their males. The tendency of assortative mating by age (more yearling x yearling and + 2‐year‐old ×+ 2‐year‐old pairs than expected by chance) showed that females chose older males when these were available.
The diet of Lapwing Vanellus vanellus chicks on Scottish farmland
Authors: GALBRAITH H.
Published: April 2008

The feeding ecology of Lapwing chicks was studied in two agricultural study areas in central Scotland. Chicks probably fed opportunistically rather than selectively and their diet was varied but comprised mainly Coleoptera, leatherjackets (Tipulidae) and earthworms.
The behaviour of seabirds foraging at fishing boats around Shetland
Authors: HUDSON A. V. , FURNESS R. W.
Published: April 2008

Among the different types of fishing vessels around Shetland, whitefish trawlers attract the largest numbers of scavenging seabirds and provide the most food. Offal was almost all consumed by seabirds, predominantly by Fulmars Fulmarus glacialis, which excluded other species by their aggression. Fulmars generally ignored discarded whole fish, which were mainly taken by Great Black‐backed Gulls Larus marinus, Gannets Sula bassana and Great Skuas Catharacta skua. Although flatfish were usually ignored because seabirds found them difficult to swallow and they sank faster, most discarded roundfish were consumed. Herring Gulls L. argentatus, Lesser Black‐backed Gulls L. fuscus and Kittiwakes Rissa tridactyla were rarely able to obtain offal or discards. Herring Gulls and Lesser Black‐backed Gulls spent much time on the periphery of feeding flocks while Kittiwakes rarely attempted even to join these. Most of the birds at trawlers were in adult plumage, and it is suggested that the low proportion of immature birds present was a further reflection of the highly competitive feeding conditions at trawlers. We suggest that likely changes in fishing practice and seabird population sizes in the immediate future may result in Herring Gulls, Lesser Black‐backed Gulls and Great Skuas finding feeding on waste around trawlers increasingly difficult, so they may be further displaced by Fulmars, Gannets and Great Black‐backed Gulls.
Organochlorines and mercury in the eggs of British Peregrines Falco peregrinus
Authors: NEWTON I. , BOGAN J. A. , Haas M. B.
Published: April 2008

The levels of various contaminants were measured in 550 addled and deserted PeregrineFalco peregrinuseggs obtained in Britain during 1963‐86. In this period the population was recovering from a low level imposed by organochlorine pesticides. Over the whole period, HEOD levels declined in eggs from both inland and coastal regions, while DDE levels declined in eggs from inland regions. At the same time, shell‐indices improved. PCB levels increased in eggs from inland regions. At any one time, levels of DDE and HEOD in eggs decreased and shell‐indices increased from south to north within Britain. These gradients fitted with the extent of agricultural land (= pesticide use) and with the extent of Peregrine population decline (both greatest in the south). No south‐north trend was apparent in levels of PCBs derived from industrial sources. In some regions eggs from coastal sites were more contaminated than eggs from inland sites, especially with PCBs and mercury. Significant relationships were found between brood sizes and DDE levels, between brood sizes and shell‐indices, and between shell‐indices and DDE levels. This implied that DDE influenced shell thickness and breeding success. Some evidence was obtained that mercury reduced brood sizes, but no evidence that HEOD and PCB (at the levels found) did so. Overall, DDE and mercury levels together accounted for 17% of the variance in brood sizes during 1963‐86. On a regional basis, DDE had no obvious effect on mean productivity when the geometric mean DDE level in collected eggs was less than 3 p.p.m., and when mean shell‐index was no more than 8% less than normal. At higher DDE levels, and lower shell‐indices, productivity declined markedly. Recovery of regional populations was associated with geometric mean HEOD levels in eggs no greater than 0–7 p.p.m., DDE levels no greater than 15 p.p.m., shell indices no more than about 15–20% below normal, and a mean breeding success exceeding 0–6 young per territorial pair.
Arrival and habitat use by Lapwings Vanellus vanellus in the early breeding season
Authors: GALBRAITH H.
Published: April 2008

The arrival on the breeding grounds and habitat use in relation to agricultural land use by Lapwings Vanellus vanellus was compared in rough grazing and arable study areas in the Midland Valley of Scotland. First arrivals took place in early February. Males preceded females and territory occupation by the males began soon after first arrival. During the pre‐breeding period birds remained in flocks and day time habitat use and activity was strongly influenced by the lunar cycle. Birds fed mainly in those habitats in which prey (leatherjackets and earthworms) were most plentiful, and in which their feeding success was high. The choice of nesting habitat was not influenced by food availability in the immediate vicinity of the nest site but by the crypticity of the clutch and incubating adults. On rough grazing birds preferred unimproved land while on arable land spring cereal was the preferred habitat. The choice of actual nesting field on the arable land was influenced by the risk of predation and the proximity of suitable feeding fields for the adults and chicks.
The relationship between daily routines of singing and foraging: an experiment on captive Great Tits Parus major
Authors: MACE RUTH
Published: April 2008

Unpaired, singing, male Great Tits Parus major kept in aviaries were subjected to two different daily regimes of foraging profitability. Birds learnt to adjust their foraging patterns to avoid feeding at periods of low foraging profitability. Once learnt, this had no effect on their singing regimes, indicating no direct causal link between the organization of daily regimes of singing and foraging. When first faced with low foraging profitability early in the morning, birds reduced morning song levels but these returned to normal, although no higher than normal, as they learnt to anticipate the daily routine. This suggests that unpredictable periods of low foraging profitability cause reduced singing activity but predictable time of day effects do not. Birds did not spend all their non‐foraging time singing and appeared to have ‘free time’.
Pigeons as seed predators and dispersers of figs in a Malaysian lowland forest
Authors: LAMBERT FRANK R.
Published: April 2008

Seven pigeon species fed on figs from at least 22 Ficus taxa at a lowland forest site in Peninsular Malaysia. Forest pigeons of the genus Treron are fig‐eating specialists. Although these are important fig‐seed predators, at least some of the population, and pigeons from other genera, potentially disperse Ficus seeds to distant sites.
The comparative breeding behaviour of two sympatric cuckoos, Horsfield's Bronze‐Cuckoo Chrysococcyx basalts and the Shining Bronze‐Cuckoo C. lucidus, in Western Australia: a new model for the evolution of egg morphology and host specificity in avian brood parasites
Authors: BROOKER M. G. , BROOKER L. C.
Published: April 2008

The breeding behaviour of two similarly sized sympatric cuckoos, Horsfield's Bronze‐Cuckoo Chrysococcyx basalts and the Shining Bronze‐Cuckoo C. lucidus, was studied over four breeding seasons at Gooseberry Hill, Western Australia. Both cuckoos usually began laying in late August; Shining Bronze‐Cuckoos laid for up to 13 weeks and Horsfield's Bronze‐Cuckoos for up to 15 weeks. Four host species were parasitized and major hosts were parasitized throughout most of their laying periods. The frequency of parasitism varied between hosts and between years, but Splendid Fairy‐wrens Malurus splendens and Yellow‐rumped Thornbills Acanthiza chrysorrhoa (major hosts) were always parasitized more heavily than Western Thornbills A. inornata and Scarlet Robins Petroica multicolor. Western Thornbills were parasitized by both cuckoos. Horsfield's and Shining Bronze‐Cuckoos laid monomorphic eggs; those of Horsfield's Bronze‐Cuckoos were highly mimetic whereas those of Shining Bronze‐Cuckoos were non‐mimetic and dark in colour. Both cuckoos laid one egg per host nest, deposited eggs directly into the nest, laid very quickly in the early morning, removed at least one host egg at laying, laid eggs small for the size of the birds, hatched after 12 days and evicted nest companions shortly after hatching. Laying was well synchronized with the start of incubation by hosts. Field observations and experiments with egg models indicated that neither of the major hosts, nor the secondary host in common, discriminate against foreign eggs. The nestling period for Horsfield's Bronze‐Cuckoo was 17 days, and for the Shining Bronze‐Cuckoo 20 days. There was a corresponding difference in nestling growth rate between the cuckoo species. About 50% of cuckoo eggs produced fledglings. Reproductive success for both cuckoos was highest in nests of the secondary host in common, the Western Thornbill. Young cuckoos reached independence 5–6 weeks after hatching. The adaptive significance of competition between cuckoos as a selective agent for cuckoo egg morphology and host specificity is discussed.
Hummingbirds of the Juan Fernández Islands: natural history, evolution and population status
Authors: COLWELL R. K.
Published: April 2008

Two hummingbird species inhabit the Juan Fernández Islands, nearly 700 km off the Chilean coast in the Pacific Ocean—the endangered endemic Juan Fernández Firecrown Sephanoides fernándensis and the continental Green‐backed Firecrown S. sephaniodes. In terms of body size, the endemic species is the most sexually dimorphic species of hummingbird known; it also displays an extraordinary degree of sexual dichromatism. Both sexes hold feeding territories, within which courtship probably occurs. It is suggested that sexual selection, and selection for gender recognition and the absence of indigenous predators may explain the evolution of sexual dimorphism and dichromatism in the Juan Fernández Firecrown. In spite of a more than twofold difference in body size, the bill lengths of both sexes in both species are nearly identical and closely match the flower tube length of the several species of endemic plants they pollinate.

The endemic Juan Fernández Firecrown has become extinct on one of the two main islands (Isla Alejandro Selkirk) and its population on the other main island (Isla Róbinson Crusoe) has greatly declined in recent decades. In contrast, the population of the Green‐backed Firecrown has probably increased on Róbinson Crusoe and the species has recently become established on Alejandro Selkirk. Because historical records show that Green‐backed Firecrown survived centuries of potential competition from Juan Fernández Firecrown, massive habitat destruction, plagues of rats, feral cats and dogs and the effects of feral livestock before beginning its recent decline, it is suggested that the introduction earlier in this century of the bramble Rubus ulmifalius, the coati Nasua nasua and possibly the rabbit Oryctolagus cuniculus may have differentially favoured the Green‐backed Firecrown at the expense of the Juan Fernández Firecrown.
The diet of Grey HeronsArdea cinereabreeding at Loch Leven, Scotland, and the importance of their predation on ducklings
Authors: MARQUISS M. , LEITCH A. F.
Published: April 2008

Regurgitations from nestling Grey HeronsArdea cinereaat Loch Leven, Scotland, April‐July 1981–83, contained mainly three types of prey:perch, brown trout and ducklings. The diet varied markedly through the season but not between years. As the heron breeding season progressed, perch occurred in fewer regurgitations and ducklings in more. There was no seasonal variation in the occurrence of brown trout. Regular collections of duckling down from the heronry suggested that the consumption of ducklings peaked in early June. The ducklings taken by herons were less than 10 days old, Mallard ducklings predominating before mid June and Tufted ducklings later. Most ducklings were taken by only a few herons:those that bred earliest and which initially fed their young on perch. Ducklings became a major part of their diet in the late nestling period and broods fed on ducklings fledged no more or fewer young than others. Herons feeding their young on brown trout took ducklings rarely, if ever. It is argued that variation in the contents of regurgitations resulted from three interacting variables; the type of feeding habitat used by individual Grey Herons, the date at which they bred and the date that regurgitations were produced by their nestlings. The numbers of ducklings taken by herons were calculated to be about 230 in 1981 and 291 in 1982, about 5% of Mallard and 3:b of Tufted ducklings estimated to have hatched annually. Assuming herons continued to consume ducklings at the same rate after their young had dispersed, the figures for Tufted ducklings would be higher but still only about 4% in 1981 and 6% in 1982. Compared with total duckling losses of over 75%, predation by Grey Herons was minor and did not affect duckling production in the years concerned.
Factors affecting the cost of polygynous breeding for female Great Reed Warblers Acrocephalus arundinaceus
Authors: URANO EIICHIRO
Published: April 2008

The male's role in feeding young and his effect on the mortality of eggs and nestlings of the Great Reed Warbler Acrocephalus arundinaceus were studied in Kahokugata, central Japan, during eight breeding seasons. Three potential costs of polygynous breeding for females were examined:(i) a reduction of male parental care per brood, (ii) an attraction of predators due to concentration of nests, and (iii) an increase of unfertilized eggs due to the reduced frequency of copulation per female. Only the first cost was found to occur:polygynous males fed their young, especially of their second broods, less frequently than monogamous ones. The lowered paternal feeding frequency, however, did not increase the mortality by starvation in second‐hatched broods. This was because the warm climate emancipated females from brooding and enabled them to compensate for the deficiency of feeding by males. The paper discusses possible roles of the staggering of the time of laying among harem mates and the shift of breeding status of females caused by nesting failure, in reducing potential costs of polygynous breeding for females.
Parental feeding in the Red‐throated Diver Gavia stellata
Authors: ERIKSSON MATS O. G. , BLOMQVIST DONALD , HAKE MIKAEL , JOHANSSON OLOF C.
Published: April 2008

We describe parental feeding by Red‐throated Divers Gavia stellata from 14.2–44.7 h of observation on each of eight pairs, coordinated with simultaneous observations at potential fishing lakes, in southwest Sweden. All pairs bred on small tarns (0.8–10 ha), normally devoid offish, and foraged in larger freshwater lakes 1.9–7.7 km away from the breeding site. Most pairs directed the majority of the foraging trips to the same lake. On average, parents made seven foraging trips per day per young. Both parents contributed to feeding activities and, in broods of two young, each chick obtained an equal amount of food. Cyprinid fish (mainly Rutilus rutilus) and salmonids (mainly Coregonus albula) dominated. Qualitative predictions from central‐place foraging theory concerning relationships between the time for a foraging trip and the size of prey delivered by a single‐prey loader were not corroborated. The amounts of fish biomass delivered were in agreement with or lower than predictions from models on daily energy requirements; this result is related to the decreased abundance of fish in acidified freshwater lakes and the decline of Red‐throated Diver populations in south Sweden.
The assessment of pesticide hazards to birds: the problem of variable effects
Authors: HART A. D. M.
Published: April 2008

The hazard presented to birds by the use of a particular pesticide is dependent on many factors and may therefore vary in its severity. Even effects which occur very infrequently may sometimes be sufficiently severe to warrant regulatory action. The potential for variability is illustrated by the effects of carbophenothion on geese and of fenitrothion on forest songbirds. Potential for the movements and behaviour of birds to vary their exposure to pesticides is illustrated using data on Tree Sparrows Passer montanus and Brent Geese Branta bernicla. Methods used in the assessment of pesticide effects are reviewed, and their ability to cope with variability is discussed. Further research is required to extend understanding of the mechanisms which cause variability, and to assess the sensitivity of methods for monitoring the effects of pesticides during commercial use.
The solution of goose damage problems in The Netherlands, with special reference to compensation schemes
Authors: EERDEN MENNOBART R. VAN
Published: April 2008

In The Netherlands farmers can apply to the Game Fund in order to receive compensatory payments in the event of damage by wild mammals and birds. In recent years the amount of money paid annually has increased up to £758,000. Although adequate as a basic measure to offset the losses suffered, the large increase in the total amount involved leads to questions about the accuracy of the estimated damage in relation to the actual crop reduction.

In certain areas in The Netherlands research is aimed at minimizing damage by altering land use in agricultural areas and restoring original habitats for wintering geese. This is a new approach for solving the apparent future conflict between a further increase of the amount of money paid to refund the damage claimed and the aims of conservation.
A comparison of yolk growth rates in seabird eggs
Authors: ASTHEIMER LEE B. , GRAU C. R.
Published: April 2008

The duration and rate of yolk deposition in the formation of avian eggs are species specific and are apparently fixed characteristics. We determined these properties for eggs from 40 species of marine birds. The mass of yolk laid down daily during rapid yolk deposition in the ovary was calculated and used to construct and compare yolk enlargement curves for each species. The spectrum of curves are all best fitted by simple second‐order polynomial regression equations, with the very rapidly enlarging yolks of Alcidae at one extreme and the slow‐forming eggs of Procellariiformes at the other. Calculated daily energy allocation to yolk deposition during the last, and most demanding, phase of yolk formation ranged from 3% to 44% of standard metabolic rate, considerably lower than other estimates.
The sympatric breeding of Larus fuscus, L. cachinnans and L. argentatus in western France
Authors: YÉSOU PIERRE
Published: April 2008

An opportunity to study the validity of the species Larus cachinnans, considered by some authors as merely a group of races related to either L. fuscus or L. argentatus, is given by its sympatric breeding with these species. Both of these latter species have recently extended their breeding range southwards, while Mediterranean representatives of the cachinnans group have spread northwards, and the three forms now breed side by side over c. 350 km along the Atlantic coast of France, where their breeding biology was studied from 1983 to 1990. L. cachinnans is very territorial, some pairs holding territories almost all year round; argentatus pairs may defend territories from mid‐winter; and the supposedly migratory fuse us are on their territories for only a short period before laying. L. cachinnans is an early breeder, laying from late March to early May, while fuscus lay from May into June, and argentatus has a protracted breeding season overlapping the other two. Interbreeding occasionally occurs; it can be productive in the case of fuscus x argentatus whereas fuscus x cachinnans attempts did not produce any young. No cachinnans x argentatus pair has been observed. This indicates strong reproductive isolation, evidence that L. cachinnans must be considered a good species.
Relationships of Australo‐Papuan songbirds‐protein evidence
Authors: CHRISTIDIS LES , SCHODDE RICHARD
Published: April 2008

Allelic frequencies determined by protein electrophoresis were used to assess relationships and familial groupings among the Australian‐New Guinean songbirds. Hypotheses of relationships were generated from the data by UPGMA, distance‐Wagner and cladistic analyses. The resulting protein‐based topologies were compared with recent DNA‐DNA hybridization studies which separate the major Australo‐Papuan families from Eurasian‐centred groups and cluster them in a single endemic radiation. Although both data sets are concordant in may areas, they differ significantly in their alignment of the Australo‐Papuan Menuridae, Climacteridae, Ptilonorhynchidae, Maluridae, Eopsaltriidae and Orthonychidae. Possible explanations for these discrepancies are examined. Both data sets otherwise agree in identifying an endemic radiation of Australo‐Papuan songbirds in which some 75% of regional species are clustered in two principal assemblages. One includes the honeyeaters Meliphagidae and their allies Epthianuridae, Acanthizidae, Pardalotidae and, arguably, Eopsaltriidae (Australo‐Papuan robins) and Orthonychidae (logrunners). The other comprises corvoid birds (Corvoidea), including Pachycephalidae, Monarchidae, Cracticidae, Artamidae, Paradisaeidae, Corvidae, Oriolidae, Campephagidae and possibly Ptilonorhynchidae (bowerbirds) amongst others. Menuridae (lyrebirds), Climacteridae (treecreepers), and Maluridae (fairy wrens) are also members of the radiation but of less certain affinity. The remaining species are grouped in a number of families forming a third assemblage of apparent Eurasian origin, the parvorder Passerida. The concept of a Gondwanan origin for the Passeriformes is canvassed.
Male colour variation in Spanish Pied Flycatchers Ficedula hypoleuca
Authors: POTTI JAIME , MONTALVO SAGRARIO
Published: April 2008

Male variation in dorsal plumage colour was studied in a montane Spanish population of Pied Flycatchers Ficedula hypoleuca. Adult and yearling males did not differ in colour as measured by Drost's colour types. However, adult males differed from yearlings in being more likely to die if they were light‐coloured the year before. Following the same individual males across years yielded a trend towards adult males becoming browner the following year, while no significant differences were found in first‐year males. For surviving individual males, becoming browner between successive breeding seasons was associated with relative delays in breeding phenology. Significant but not very high repeatability of male colour is found, and this trait may be subjected to moderate environmental variation, perhaps while moulting in the winter quarters. Overall, being browner may be a sign of ageing and/or poor condition in Spanish Pied Flycatchers.
Foraging range and feeding locations of Shags Phalacrocorax aristotelis during chick rearing
Authors: WANLESS S. , HARRIS M. P. , MORRIS J. A.
Published: April 2008

We used radio‐tracking techniques to determine the foraging range and feeding locations used by individual Shags Phalacrocorax aristotelis during chick rearing on the Isle of May, Scotland. The mean (±s.d.) foraging range was 7.o±1.9 km (maximum 17 km) and there were no significant sex or year differences. All feeding sites were within 7 km of land. Most (> 90%) were either within 2 km of the colony or in two discrete areas 5–13 km to the north and west. Use of the areas varied between years with both males and females making more use of the north area in 1987 than either 1988 or 1989. Birds used > 11% of the area of sea within the maximum recorded feeding range. This restricted distribution appeared to be related to water‐depth and bottom sediment type. Shags fed most frequently in water 21–40 m deep, with a bottom of either gravel and sand, or rock with thin patchy sediment cover.
Diving depths of Shags Phalacrocorax aristotelis breeding on the Isle of May
Authors: WANLESS S. , BURGER A. E. , HARRIS M. P.
Published: April 2008

Information on maximum dive depth and the time spent at various depths was obtained from 49 Shags Phalacrocorax aristotelis. On average, the maximum dive depth was 33–35 m; the overall maximum was 43 m. Shags dived repeatedly to the same depth and spent c. 55% of the time between 25 and 34 m which indicated that they were foraging close to the seabed. About 46% of the time underwater was spent foraging and 54% travelling. Average underwater swimming speed was 1.7‐1.9 m per second.
A meta‐analytic study of the effects of female age on laying‐date and clutch‐size in the Great Tit Parus major and the Pied Flycatcher Ficedula hypoleuca
Authors: JARVINEN ANTERO
Published: April 2008

The effects of age (1 year‐old vs older females) on laying‐date and clutch‐size of the Great Tit Parus major (in eight independent study areas) and the Pied Flycatcher Ficedula hypoleuca (five areas) were meta‐analysed using both published and unpublished records. To standardize comparisons between areas and species, the standardized difference between the means of the two age groups was used as a measure of the magnitude of the age‐effect (effect size).

In Great Tits the laying‐date of ‘young’ females was 0.30 standard deviation units later and clutch‐size 0.31 units smaller than that of ‘old’ females. In the Pied Flycatcher the corresponding figures were 0.45 and 0.81, respectively. All the effect size measures were highly significant but for clutch‐size the effect size of the Pied Flycatcher was significantly greater than that of the Great Tit. In the Great Tit the effect size of clutch‐size was heterogeneous across the different study areas.

It was estimated that the following numbers of unpublished studies showing null results would have to have accumulated in file‐drawers before we could say that the results concerning effect sizes are due to sampling bias: for Great Tits 121 studies of laying‐date and 196 studies of clutch‐size; and for Pied Flycatchers 45 studies of laying‐date and 139 studies of clutch‐size.
The effect of a period of food restriction on gonad size and moult of male and female Starlings Sturnus vulgaris under constant photoperiod
Authors: MEIJER THEO
Published: April 2008

The effects of food availability on the reproductive cycle and on the timing and duration of moult were investigated in first‐year male and female Starlings Sturnus vulgaris under a constant photoperiod of 12 hours. A 20% lower body mass during the first 9 weeks of restricted feeding had a slight negative effect on testicular growth during the first 3 weeks of the experiment and delayed the onset of moult for 12 days after the return to ad libitum feeding conditions. No effects were found on changes of beak colour and moult duration of males. Females exposed to the shorter feeding time similarly showed a reduced body mass (21%) but compared with controls, did not differ in beak colour, in follicle growth, or in the onset and duration of moult. In contrast to males, body mass of the experimental females after the food restriction period remained lower for more than 6 weeks, compared to control birds. Females had a longer reproductive cycle and started moult later than males. The later an individual started to moult, the faster it moulted. Two females started to moult extremely late and did not moult their first primaries.

These results indicate that in male Starlings food restriction slightly affected the rate of photoinduced gonadal growth and the onset of postnuptial moult. These effects were not observed in females subjected to the same experimental conditions.
Organochlorines and mercury in the eggs of Golden Eagles Aquila chrysaetos from Scotland
Authors: NEWTON I. , GALBRAITH E. A.
Published: April 2008

This paper documents the organochlorine levels found in unhatched eggs from 234 clutches of Golden Eagles Aquila chrysaetos obtained in Scotland during 1963‐86. Organochlorine levels were highest in eggs from western coastal districts, somewhat lower in eggs from western inland districts, and lower still in eggs from eastern districts. These regional trends were associated with corresponding dietary differences.

Levels of HEOD declined in western districts during the period 1963‐86, but not in eastern districts where they were low throughout. Levels of DDE declined generally, but significantly only in the east. In contrast, levels of PCBs increased generally, but significantly only in western inland districts.

No differences in organochlorine levels were found between clutches that produced no young and those that produced one young.

Mercury residues were examined in eggs from 66 clutches obtained during 1981‐86. Low levels were detected in 10 out of 29 eggs from western coastal districts, in 2 out of 27 eggs from western inland districts, and in none out of 10 eggs from eastern districts.
The relationship between body size and time of breeding in Icelandic Redshanks Tringa t. robusta
Authors: SUMMERS RONALD W. , UNDERHILL LESLIE G.
Published: April 2008

The average wing‐lengths of male and female Redshanks differ, allowing one to estimate the probabilities of males being larger in pairs whose measurements are known. Using these probabilities in a large number of simulations we showed that larger ‘female’ Icelandic Redshanks nested earlier than smaller ones. The results support Hale's suggestion that size selection in Redshanks operates on the breeding grounds. There was no evidence of assortative mating.
The cost of incubation in relation to clutch‐size in the Collared Flycatcher Ficedula albicollis
Authors: MORENO JUAN , GUSTAFSSON LARS , CARLSON ALLAN , PÄRT TOMAS
Published: April 2008

This study examines the importance of avian incubation costs as determinants of clutch‐size variation by performing clutch‐size and brood‐size manipulations in the same population of Collared Flycatchers Ficedula albicollis during the same breeding season. In 2 5 cases when three or more clutches of the same size were completed on the same day, we moved two eggs on the day after the last egg had been laid from one randomly selected clutch (C) to another (C) and moved two other eggs from this to a third clutch (C+). In 20 other cases of simultaneously completed clutches of the same size, we moved two randomly selected young from one brood to a second and from that moved two other young to a third (B, B and B+groups). Most females were weighed the day after completion of the clutch and 1–4 days before hatching of the young, and some of them also 10–14 days after hatching of the young. We measured the daily energy expenditure of females incubating manipulated clutches of 4, 6 and 8 eggs by means of the doubly‐labelled water (D218O) technique and also recorded their nest attendance. Hatching success of fertilized eggs was reduced in the enlarged clutches compared with control and reduced clutches. Females expired on average 3142.6 ml CO2 and expended 78.6 kJ per day while incubating, which corresponds to a metabolic intensity of 3.3 times BMR. Daily energy expenditure increased with clutch‐size due to higher costs while incubating, and not because of changed activity patterns. There were no significant differences in length of incubation, female mass or mass changes between phases for the C, C and C+groups. In both the C and B groups, enlarged broods produced significantly more fledged young than control broods, and those significantly more than reduced broods. Fledgling tarsus‐length and mass did not differ significantly between treatments in either the C or B groups. There was no significant difference in breeding success between clutch and brood manipulations. In this season, incubation costs did not entail significant fitness losses, expressed either as fledgling production or female condition. Also, control females could have raised more young to fledging age than they did with no apparent costs.
The experimental paradigm and long‐term population studies
Authors: KREBS CHARLES J.
Published: April 2008

Most ecologists recognize the value of long‐term studies to population and community ecology, and many also subscribe to the experimental approach as the most effective way of obtaining ecological knowledge. But if we are experimentalists, do we need long‐term studies? I argue that the answer to this question is yes, that we must combine these two approaches to solve the major ecological questions of the next century. Most of the challenging questions facing ecologists involve systems subject to long‐term time trends or high environmental variability.

Because of the statistical power of many ecological methods, long‐term studies are essential to measure time trends in ecosystems. Ignoring statistical power has been a major problem with short‐term studies, which have predominated in the ecological literature.

Some examples of long‐term studies on larch bud‐moth Zeiraphera diniana, winter moth Operophthera brumata and snowshoe hares are discussed briefly to illustrate the four major desiderata of long‐term projects: spatial scale, sampling design, hypothesis testing and timeframe.

Two reasons for not doing long‐term studies are to assess density‐dependence and to monitor ecosystem health. The density‐dependent paradigm is bankrupt and has produced much argument and little understanding of population processes. Monitoring of populations is politically attractive but ecologically banal unless it is coupled with experimental work to understand the mechanisms behind system changes.
Population studies of the Fulmar on Eynhallow, Orkney Islands
Authors: DUNNET G. M.
Published: April 2008

This short paper describes the background, initiation and development of what has turned out to be a long‐term (41 years to date) study of Fulmars on Eynhallow in Orkney. Most of the scientific results have been published (see Appendix 1) so that only the major findings will be referred to here, to illustrate how the study has evolved as knowledge increased, new techniques became available and objectives changed.
Long‐term bird population studies in the United States
Authors: O'CONNOR RAYMOND J.
Published: April 2008

Long‐term population studies of birds in the United States have been less species‐oriented and more concept‐oriented than in Britain. The demographics of North American species do not differ grossly from those of species elsewhere in the world, but polygamy has been relatively more frequently studied in U.S. species than elsewhere. Subjects that have been particularly explored in long‐term studies in the United States include the determinants of cooperative breeding in birds, the effects of the spatial scale on what is learned, and correlates of regional and national declines in bird populations. Other areas of developing interest include the potential uses of monitoring data, the relative value of longitudinal and cross‐sectional studies in analysing slow processes, and the significance of episodic events in shaping population patterns.
A long‐term study of Short‐tailed Shearwaters Puffinus tenuirostris on Fisher Island, Australia
Authors: BRADLEY J. S. , SKIRA I. J. , WOOLLER R. D.
Published: April 2008

All 100–200 Short‐tailed Shearwaters Puffinus tenuirostris breeding on Fisher Island, in Bass Strait, Australia, have been individually marked and their breeding performance monitored in each year since 1947. This long study has revealed that mortality rates are greater in older shearwaters and that reproductive performance varies with age, breeding experience and mate familiarity in complex ways. A single study population proved inadequate, however, for estimating pre‐breeding survival rates, recruitment rates, emigration and immigration.
The effect of maternal age and experience on egg‐size and hatching success in Wandering Albatrosses Diomedea exulans
Authors: CROXALL J. P. , ROTHERY P. , CRISP A.
Published: April 2008

The roles of maternal age and experience, on the one hand, and individual, year and random effects on the other, in influencing avian egg‐size and hatching success have been much debated but seldom studied comprehensively. We investigated these topics with Wandering Albatrosses Diomedea exulans of known age (7–30 years) and experience (1–8 breeding attempts) over a 10‐year period. Older and more experienced birds laid larger eggs. After allowing for year and controlling for experience, significant age effects remained; after controlling for age, no detectable experience effects remained. However, age accounted for only 6% of the overall egg‐size variation. Egg‐size varied significantly between years and has increased over the last decade. Individuals laid eggs of consistent sizes; 55% of the random variation in egg‐weight was due to such effects. Egg‐ and hatchling‐weight were very closely linked; larger eggs also had higher hatching success. The latter was influenced significantly by age and experience but neither remained significant after controlling for the other. Year effects were also detectable.

That there are significant effects of age, experience, year and individual on egg‐weight (and hatching success) is probably typical of seabirds generally, though with different balances between factors depending on species and situation; however, insufficient data exist to examine this critically. Our finding that age was a more important influence than breeding experience does not support recent suggestions that hatching success is mainly influenced by experience and that experience will have a greater effect on reproductive success in long‐lived species with high mate‐fidelity. However, Wandering Albatrosses may have acquired much relevant experience before even starting to breed.
Habitat selection and coexistence of migrants and Afrotropical residents
Authors: LEISLER BERND
Published: April 2008

In this paper I discuss factors that influence the habitat choice of small migrant birds on their Afrotropical wintering grounds and the ecological isolation of migrants and residents. The main characteristic of migrants is the use of resources which are sporadic in space and time. The majority of migrants occur in seasonal savannas and open woodland, mostly using temporarily and locally abundant food sources generally unused by residents. Migrants are more eurytopic and exploit more open parts of the habitats than ecologically similar tropical species. In some guilds, the foraging speed and rate of migrants is higher and they use their wings more often in comparison to residents. There is weak evidence that niche shifts of residents are induced by the arrival of migrants. Overt interspecific interactions seem to be infrequent, except in a guild of ground‐feeding birds which rely on a rather predictable but poor food supply. In this guild, residents, but not intra‐African migrants, dominated Palaearctic migrants in aggressive encounters irrespective of body‐size. In contrast to this, dominance was size‐dependent among wintering Palaearctic migrants.