bluuebunny/crossref_metadata_2025_split huggingface dataset:
ABUNDANCE AND SEASONALITY OF THE SAVANNA AVIFAUNA AT PORT MORESBY, PAPUA NEW GUINEA
Authors: BELL H. L. 
Published: April 2008

SummaryThe results of 156 transect counts carried out over 30 months in savanna of the Coastal Hill Zone, Port Moresby, Papua New Guinea, are analysed. The avifauna is depauperate compared to similar habitats in New Guinea and temperate Australia. Twelve common species of the Port Moresby savannas were not so in the Coastal Hill Zone and reasons for their rarity are given. Most species present are solely savanna forms but some are dependent upon the presence of small patches of monsoon forest. Average density of birds was estimated at 55 per 10ha, a very low figure compared to New Guinean rainforests. Carnivores and mixed‐feeders make up two thirds of numbers present but frugivores, because of their large individual size, are a significant proportion of biomass. There was little significant seasonal difference in overall numbers except for granivores which decline in numbers during the wet season. However, individual species show regular seasonal fluctuations reasons for which are postulated. A correlation exists between flowering of trees and numbers of certain species, and also between the annual grass‐fires and numbers of certain grassland species. Merops ornatus, Lalage sueurii and Coracina novaehollandiae, considered in the literature to be wintering migrants, are also shown to be breeding residents. Breeding records for 462 species were analysed. Most breeding of insectivores and mixed‐feeders occurs in the Austral spring during the dry season and ends before the onset of heavy rains. Granivores breed in the late wet season. The few records for frugivores indicate a wet season peak.
EGG COMPOSITION AND HATCHLING PRECOCITY IN SEABIRDS*
Authors: WILLIAMS A. J. , SIEGFREID W. R. , COOPER J. 
Published: April 2008

SummaryThis paper presents analyses of the composition (shell, yolk, albumen) and of the quality (lipid, protein and water contents) of yolk and albumen of eggs of 25 species of seabirds belonging to the Sphenisciformes, Procellariiformes, Pelecaniformes, and Lari of the Charadriiformes. These data are compared with those published for species in the same orders and suborders, and the combined seabird data are compared with published data for non‐seabirds.Variation in the proportionate weight of eggshell is not related to hatchling precocity but is probably due to adaptive differences in nest substratum and the agility of the incubating birds. Lipid and protein contents of yolk, and water content of albumen, are uniform in eggs of all examined species. Protein levels of albumen and water content of yolk and of entire egg contents vary greatly between taxa.Contrary to previous claims there is no simple relationship between egg composition and hatchling precocity. Differences in egg composition will probably only be clearly understood when the nutritional needs of the embryo, and of the hatchling in the time before it regularly obtains food, are known.
Habitat selection, foraging niches and horizontal spacing of Willow Warbler Phylloscopus trochilus and Chiffchaff P. collybita in an area of sympatry
Authors: Sæther Bernt‐Erik 
Published: April 2008

Habitat selection of the Willow Warbler and the Chiffchaff was studied along a succession of grey alder forest in Central Norway (63oN) where both species breed. Both were found in all serai stages, but there was a slight tendency for the Willow Warbler to be found more often in the voungest stages than was the Chiffchaff.Foraging niches and horizontal spacing were studied within one particular forest. Most of the records of both Willow Warbler and Chiffchaff came from the tree layer, and the overlap between the species in their foraging niches was considerable. However, the species were found to occupy almost mutually exclusive territories.
A revision of the babbler genus Trichastoma and its allies (Aves: Timaliinae)
Authors: RIPLEY S. DILLON , BEEHLER BRUCE M. 
Published: April 2008

By means of a comparative analysis of 12 morphological and behavioural characters, the timaliine genus Trichastoma and its relatives in the tribe Pellorneini are revised to reflect new understanding of inter‐ and intrageneric relationships (cf. Mann et al. 1978). Trichastoma as constituted by Deignan (1964) is here subdivided into three unambiguously monophyletic genera, the Malayan Trichastoma and Malacocincla, and the African Illadopsis.Evidence is presented indicating that the reconstituted Trichastoma should be considered the stem genus for the tribe. Reviewing the distribution of morphological and behavioural characters, the general implication is that the African forms share a recent common ancestor with those from Asia. Distributional data support the contention that the group originated in the Malayan region and colonized westward through southern Asia and Arabia to Africa (probably in early Quaternary) when humid and warm conditions fostered a continuous Afro‐Asian corridor of tropical wooded habitats. The postulated greater age of the pellorneine assemblage in Malaysia, along with the region's insular geography, has fostered a larger species radiation than that in continental Africa. Recent desiccation of Arabia and central and northwestern India probably caused widespread regional extinction of linking forms and has isolated the Pellorneini into two humid forest refuges in equatorial Africa and eastern Asia.
Factors affecting duckling survival of Eiders Somateria mollissima in northeast Scotland
Authors: MENDENHALL VIVIAN M. , MILNE H. 
Published: April 2008

Mortality factors affecting Eider ducklings Somateria mollissima and their impact with respect to age were studied on the Ythan estuary, Aberdeenshire, Scotland. Survival from hatching to fledging averaged 10.4% over 13 years; numbers declined steeply during the first three to four weeks and slowly thereafter. Growth of tagged young varied considerably between broods. Mortality was not correlated with numbers of ducklings or adults.Predation in 1974 averaged 13.6% per day during the first two weeks, and accounted for most mortality. Herring Gulls Larus argentatus were the principal predators. Predation was 2.5 times as high in rainy, windy weather as in fine, calm weather. Weather, primarily mean rainfall and wind speed, during early life accounted for over 90% of all variation in survival during eight of nine years. Predation was considered the proximate factor in most weather‐related mortality. High survival in 1971 was not explained by weather. An estimated 25–40% of mortality during the second week of life was from renal coccidiosis Eimeria somateriae. Reproductive output of the Ythan population probably limits the rate of population growth, but numbers of breeding birds seem to be regulated by other factors acting after fledging.
Mating system and nesting biology of the Red‐necked Phalarope Phalaropus lobatus: what constrains polyandry?
Authors: REYNOLDS JOHN D. 
Published: April 2008

In this five‐year study of Red‐necked Phalaropes on the coast of Hudson Bay, Canada, only 8% (5/59) of females were polyandrous. Seventy‐five percent were monogamous, and 17% did not obtain mates. All males obtained mates readily. To understand the low incidence of polyandry in this sex‐role reversed, non‐territorial mating system, aspects of the pair bond, nesting biology, and size and plumage dimorphism were examined.Pair bonds lasted an average of 11 days and ended as soon as the clutch was completed. Polyandrous females initiated their second nests only seven days later. Since in most years nest initiation for the population as a whole spanned three weeks, there was ample time for multiple clutches. Energetic constraints may have played a limited role in constraining polyandry, but many females that had previously laid clutches courted incubating males or harassed pairs.The major factor limiting polyandry appeared to be availability of mates. Because phalaropes generally breed in habitats that are less defensible than those of other role‐reversed shorebirds, they are less able to monopolize males in populations with equal sex ratios. Sexual size dimorphism is correspondingly smaller than in territorial role‐reversed shorebirds, although plumage variation between and within sexes in this study was strong (and invariant with age). Thus, despite the phalaropes' role‐reversal, the evidence indicates that monogamy may predominate, with sexual selection driven by the ability of females to produce second clutches opportunistically when receptive males are available.
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.
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.
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 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 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 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.
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.