bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effects of changing agricultural practice upon Woodpigeon Columba palumbus numbers
Authors: INGLIS I. R. , ISAACSON A. J. , THEARLE R. J. P. , WESTWOOD N. J. 
Published: April 2008

The Woodpigeon Columba palumbus population in a 1070 ha study area in East Anglia was studied from 1961 to 1986. This paper relates variations in Woodpigeon numbers to changes in the areas and types of crops grown.In the early 1960s the mean Woodpigeon population fluctuated between 60 and 112 birds per 50 ha during the winter months. Subsequently there was a steady decline until the population levelled out in the early 1970s at around 30 birds per 50 ha. From a very low point in 1977, the numbers of birds increased reaching in 1986 a mean of 55 birds per 50 ha.Marked changes occurred in the types of cereals grown in the area. In the 1960s spring‐sown barley was the major crop with winter‐sown wheat occupying most of the remaining area. Throughout the 1970s winter wheat was increasingly grown and winter‐sown barley replaced the spring‐sown variety. Although the area of permanent pasture did not change significantly, the area of clover ley was reduced markedly in the late 1960s. In the mid 1970s silage and oilseed rape were introduced and the cultivation of peas was expanded. On the basis of the crop types grown, the study period was divided into two 11‐year blocks 1961–1971 and 1975–1985. Crop preferences of Woodpigeons were calculated for each month within each of these 11‐year periods. A series of stepwise regressions was then conducted on both of the 11‐year periods in order to see how well the areas of preferred crops in a particular month could account for the mean population size of that month.In the winters 1961/62 to 1971/72 the winter Woodpigeon population size was influenced by two crops. The area of cereal sowings largely determined how many birds remained in the area in December. The availability of clover ley, which depended upon both the area of clover ley and the amount of snow cover, controlled the population size in January and February.In the winters 1975/76 to 1985/86 the population size was again affected by two crops. In November the amount of grain on both stubbles and sowings influenced how many young birds stayed in the area. The area of oilseed rape in December then set the population size which changed very little throughout the rest of the winter.The change in the pattern of population regulation has profound implications for the likely success of shooting Woodpigeons in winter as a means of reducing local numbers.
Energetic demands during brood rearing in the Wheatear Oenanthe oenanthe
Authors: TATNER PAUL 
Published: April 2008

Daily energy expenditure of Wheatears Oenanthe oenanthe during the brood rearing period was measured using the doubly‐labelled water technique. The average daily metabolic rate (ADMR) (± 1 s.d.) for 24 individuals was 6.24 ± 1.17 cm3 CO2/g/h, which corresponds to 95.3 ± 17.0 kJ/day (RQ = 0.75) for a bird of average mass (24.3 g).There were no significant differences in daily energy expenditure between the sexes, nor between first‐year and older birds. Individual males with longer tarsi had lower ADMR but raised larger broods. The ADMR increased at lower ambient temperatures, but this effect disappeared when the positive correlation with rainfall was taken into account. There was no relationship between the natural brood‐size and parental daily energy expenditure. A positive correlation between ADMR and the time spent hopping and pecking suggests that foraging activity may account for some of the variability between individuals. The daily change in body‐mass was not related to either the individual's age or its sex, and overall was not correlated with the level of daily energy expenditure. For birds examined on the same day, individuals with a higher ADMR had a greater loss of body‐mass, which appears to be a high risk strategy. However, Wheatears also exhibited an ability to increase body‐mass in conjunction with a drop in their daily energy expenditure.
Optimal fat loads and long‐distance flights by migrating Knots Calidris canutus, Sanderlings C. alba and Turnstones Arenaria interpres
Authors: GUDMUNDSSON GUDMUNDUR A. , LINDSTRÖM ÅKE , ALERSTAM THOMAS 
Published: April 2008

Arctic waders often build up large fat loads and complete their migratory journeys by a few long‐distance flights between traditional staging sites. Optimal fat loads and choices of staging sites differ depending on whether the birds are adapted to minimize energy or time spent on migration. In the latter case, we predict that the birds will depart for the next staging site when the instantaneous speed of migration expected after arrival at the next site, exceeds the corresponding speed at the departure site. The instantaneous migration speed is a function of the rate of fat deposition and the current fat load. As a consequence of this, overloading (birds deposit larger fat loads than needed merely for covering the flight distance to the next destination) and by‐passing of possible, but low‐quality staging sites, are expected under specific conditions in time‐selected migration.Estimates of fat deposition rates and departure fat loads were obtained by captures of Knots Calidris canutus, Sanderlings C. alba and Turnstones Arenaria interpres in W. Iceland during spring migration. Further fat deposition data referring to spring migration of these species were compiled from the literature. Fat deposition rates at different sites, as measured by the daily gain in mass relative to lean body‐mass, range between 1.0 and 3.6%/day, and departure fuel loads (in % of lean body‐mass) between 27 and 73%.Comparison with flight range estimates suggests that overloading may be a regular phenomenon during spring migration of Knots, Sanderlings and Turnstones. Furthermore, fat deposition rates at different staging sites, and the general difference in migration patterns between spring and autumn, indicate that by‐passing of possible staging sites may well occur. Hence, it cannot be excluded that the waders' migratory habits primarily serve to maximize the overall speed of migration.
Proper Studies and the Art of the Soluble
Authors: TAYLOR L. R. 
Published: April 2008

The Art of the Soluble‘No scientist is admired for failing in the attempt to solve problems that lie beyond his competence.If politics is the art of the possible, research is surely the art of the soluble. Both are immensely practical‐minded affairs.Good scientists study the most important problems they think they can solve. It is, after all, their professional business to solve problems, not merely to grapple with them.That is why some of the most important biological problems have not yet appeared on the agenda of practical research.’Proper Studies‘Atoms are immeasurably less complicated than man. And yet nobody who is not professionally a physicist would venture to discuss the nature of atoms. Where man is concerned. the case is different.’
Geese and their future fortune
Authors: OWEN MYRFYN , BLACK JEFFREY M. 
Published: April 2008

Wild goose populations were probably limited by winter food supplies before Man modified their winter range and effectively removed that limitation on population growth. At the same time, reduction of hunting lowered Man‐induced mortality and allowed most populations to increase both in Europe and in North America.This paper considers likely future trends, and, using the population of Barnacle Geese breeding in Svalbard as an example, suggests how numbers might be regulated in a density related manner. The Svalbard Barnacle Goose population has shown a decline in recruitment rate and an increase in the natural mortality rate as numbers have increased. Both of these are reflections of competition on the breeding grounds, though there may be some effects at other times. We suggest that most populations will eventually be limited by resources on the breeding area.Some of the implications of changes in numbers are that pair‐bond stability and breeding area philopatry are less advantageous and in time will become less pronounced as the selective value of these traits are diminished.We argue that both for applied reasons (conservation, crop damage prediction) and for academic investigations of population processes, long‐term studies are vital in the management and understanding of goose populations. A number of features of their life history make geese very suitable subjects for such studies.
Greenshanks Tringa nebularia and long‐term studies of breeding waders
Authors: THOMPSON P. S. , THOMPSON D. B. A. 
Published: April 2008

Despite great variation in breeding, social and migration systems, there have been few long‐term (more than 5 years) studies of waders. This paper describes a 27‐year study of breeding Greenshanks Tringa nebularia, and briefly reviews the scope for long‐term work on breeding waders in the Western Palaearctic.Between 1964 and 1990 a Greenshank population in NW Scotland varied threefold in number but declined during the 1980s. Some territories were occupied almost every year whereas others became unoccupied. The increase up to the mid 1970s coincided with good summer weather likely to improve breeding success and subsequent adult recruitment. The decline occurred despite no adverse change in weather, an increase in over‐winter numbers on British and Irish estuaries, and no increase in nest predation. Afforestation in the Flow Country of northern Scotland may have exacerbated the decline by reducing numbers of potential recruits from what were once productive areas. Habitat for broods has deteriorated considerably in the study area because of the impact of all‐terrain vehicles: pool complexes have deteriorated to a greater degree in unoccupied than in occupied territories. Territories with most disturbance have been occupied less regularly. There has been a decline in habitat structural complexity likely to render chicks more prone to predation and less likely to find preferred food. Habitat is now set to recover, and predictions are made about the Greenshank's response.Of 47 wader species breeding regularly in the Western Palaearctic, none have had lifetime reproductive success measured and long‐term population dynamics have been studied in only nine. We provide a list of species that might be appropriate for addressing six important ecological issues. Five emerge as common targets for further long‐term work: Dotterel Charadrius morinellus, Lapwing Vanellus vanellus, Avocet Recurvirostra avosetta. Common Sandpiper Actitis hypoleucos and Curlew Numenius arquata.
Perspectives on Palaearctic and Nearctic bird migration; comparisons and overview of life‐history and ecology of migrant passerines
Authors: MÖNKKONEN M. , HELLE P. , WELSH D. 
Published: April 2008

In this paper we compare ecological attributes of tropical migrant passerines from the Nearctic and western Palaearctic, focusing particularly on habitat association patterns during both breeding and wintering seasons. Three regions were compared: Europe, western and eastern North America. Breeding bird census data from 32 studies (each including at least four stages of forest succession) were used to assess the association patterns of breeding habitats among tropical migrants. For each species we calculated an index of habitat diversity and habitat preference.Tropical migrants preferred earlier successional stages than other birds in Europe. The opposite was true in eastern North America. In eastern North America, tropical migrants tended to be associated with a smaller range of serai stages than other passerine species. In their winter quarters, Palaearctic migrants live primarily in open habitats, such as savannas, whereas eastern Nearctic migrants make more frequent use of evergreen forests. Migrants from western North America show the greatest match between breeding and wintering habitats.We relate the results to the taxonomy and probable history of contemporary avifaunas and vegetation formations of the Old and New World. Taxonomically, tropical migrants from different parts of the Holarctic are less closely related to each other than residents and short‐distance migrants. Tropical and temperate avifaunas are more closely related to each other in the New World than in the Old World. Conservation implications of the between‐continent differences are briefly discussed.
A comparison of digestive efficiency in birds of prey
Authors: BARTON NIGEL W. H. , HOUSTON DAVID C. 
Published: April 2008

Differences in how raptors hunt and what they catch are correlated with size‐independent differences in length of the small intestine, the region of the digestive tract responsible for food absorption. The study examined the functional significance of these differences among ten raptor species. Dry matter apparent digestive efficiency was calculated for each species fed a diet of day‐old cockerels. For Falconiformes and Strigiformes, efficiencies varied between 75% and 82%, digestive efficiency being positively correlated with intestine length.Generalist species, with a wide prey spectrum and feeding on relatively easily caught prey and carrion, had long intestines and high digestive efficiencies. Raptors specializing on fast‐moving, avian prey had short intestines and reduced digestive efficiency. The Peregrine Falco peregrinus and the Common Buzzard Buteo buteo were used as examples of specialist and generalist feeders, respectively. Rabbit and pigeon were fed to both. Buzzards digested both diets more efficiently than Peregrines. Body‐mass changes were used to examine the nutritional value of the two diets to each species. Buzzards gained body‐mass when eating rabbit, Peregrines lost mass. Both species gained mass when feeding on pigeon. It seems that consideration of diet quality, not just quantity, is essential in understanding raptor food requirements. Generalist raptors have high efficiencies on several diets, specialists compensate for their reduced efficiency by eating food of high nutritional quality. Various aspects of prey quality are examined.
Flock feeding and food intake in Little Egrets Egretta garzetta and their effects on food provisioning and reproductive success
Authors: HAFNER H. , DUGAN P. J. , KERSTEN M. , PINEAU O. , WALLACE J. P. 
Published: April 2008

Food provisioning to chicks of Little Egret Egretta garzetta in a colony at Ligagneau in the Camargue, southern France, was measured using electronic nest balances. Both pair members supplied food to the chicks, and each performed three to five alternating foraging trips.The loading rate during the first trip of the day (1.09 g/min) was more than three times as high as that during later trips (0.32 g/min) and accounted for 20% of the daily amount of food delivered. This food was collected while the birds were feeding in dense aggregations on mosquitofish which had become temporarily concentrated due to hypoxic conditions overnight in the surrounding marsh. Later in the day, when this concentrated food source was no longer available, the birds fed solitarily.The total amount of food delivered per day remained constant at 385 g as chick age increased from 10 to 20 days. Given the observed loading rates, 385 g is near the maximum amount of food the pair can deliver during a 16.5‐h daylight period when they forage continuously throughout the day but only one parent at a time. This indicates that a time constraint limits the amount of food delivered to a brood during this stage of the breeding cycle. Given this time constraint, the total amount of food delivered per day would have been reduced by 25% if the birds had not been able to benefit from the concentrations of mosquitofish during the early morning.Breeding success was significantly higher at Ligagneau (3.25 chicks/nest) than in other Camargue colonies (2.69 chicks/nest). In addition, post‐fledging survival of chicks with a low rank in the brood hierarchy was probably better at Ligagneau than elsewhere in the Camargue. We attribute this elevated reproductive output at Ligagneau to the exceptionally large amount of food collected by egrets during the early morning aggregations, which were probably formed in response to predictable concentrations of mosquitofish in the permanent marshes surrounding this colony. Such aggregations were rarely observed in the temporary marshes surrounding the other colonies, probably because the occurrence and location of fish concentrations are difficult to predict in this habitat due to rapidly falling water levels.
Adult survival and numbers in a coastal breeding population of Redshank Tringa totanus in northwest England
Authors: THOMPSON PATRICK S. , HALE W. G. 
Published: April 2008

The results of a long‐term capture‐mark‐recapture ringing programme carried out on a coastal population of breeding Redshanks Tringa totanus between 1974 and 1988 are presented.Both sexes were equally likely to be recaptured in subsequent years, as were birds captured for the first time compared with those that had been captured previously. Older birds were more frequently recaptured than were young birds. There was no significant difference in male and female adult survival rates, with a mean of 72% of females and 75% of males surviving each year.The breeding population fluctuated annually with estimated breeding densities of 122–285 pairs per km2. Variation in breeding numbers (males), but not survival, was partially attributable to winter air temperature.
The breeding biology and causes of nest failure of Scottish Black‐throated DiversGavia arctica
Authors: MUDGE G. P. , TALBOT T. R. 
Published: April 2008

The breeding biology and causes of nest failure were examined for Black‐throated DiversGavia arcticain core areas of their Scottish breeding range in 1983–1987. Breeding was confirmed for up to 88% of territorial pairs each year (n= 28–62), and 76% of nests were on islands. Hatching success was consistently low with, on average, only 43% of territorial pairs managing to hatch a clutch each year; 64% of recorded nest failures occurred during the first week of the 4‐week incubation period.Overall breeding success in West Sutherland in 1984–1987 averaged 0.23 chicks per territorial pair per year, while in Ross‐shire for 1986–1987 it was 0.29. Forty percent of hatched chicks survived to fledge, and 92% of recorded deaths occurred in the first fortnight after hatching; 4.8% of fledged broods held two chicks.Causes of nest failure were assessed with the aid of surveillance cameras. Approximately 30% of losses were due to water level changes (mostly floods), 48% to predators (primarily nocturnal mammals, but also Hooded CrowsCorvus corone), 13% to human egg collectors and 5% to desertion following human disturbance.Scottish Black‐throated Divers produce only half the number of chicks tentatively estimated to be required to maintain a stable population. The main difference between the Scottish and more successful Swedish populations is in the degree of chick mortality.
Bird interactions with utility structures: collision and electrocution, causes and mitigating measures
Authors: BEVANGER KJETIL 
Published: April 2008

The causes of collision and electrocution accidents involving birds and power lines, and measures to mitigate such accidents, are reviewed. It is convenient to group the causes according to (1) biological, (2) topographical, (3) meteorological and (4) technical aspects. As regards collisions with power lines, the important biological variables are connected with the morphology, aerodynamic capability, physiology, behaviour and life‐history strategies of birds. To understand the electrocution problem, the relationship between body size and electrocuting installations must be considered.Removing earth wires (and modifying earthing methods). modifying line, pole and tower design, installing underground cables and conspicuous marking of lines, poles and towers are important measures for tackling the problems. The route planning process should include careful mapping of (1) topographical features which are leading lines and flight lanes for migrating birds and/or are important for local movements of resident species, (2) topographical elements such as cliffs and rows of trees that force birds to fly over power lines, (3) primary ornithological functions or uses of the area to avoid key areas for birds and avoid separating these areas and (4) local climatic conditions (including seasonal variations) like fog frequency and prevailing wind direction. The outcome depends largely on a combination of these factors.Objective assessment of the effects of mitigating measures, in particular wire marking, is required. The mitigating efforts should be directed against species known to be potential collision victims, and their design should be the result of a careful analysis of the biology and ecology of the target species.Because of the cumulative effects of negative impacts on bird populations today and the alarming number of species with endangered or vulnerable status being killed in connection with utility structures, the problem deserves increased general awareness.
The winter feeding ecology of Avocets Recurvirostra avosetta on intertidal areas. I. Feeding strategies
Authors: MOREIRA FRANCISCO 
Published: April 2008

The behaviour of Avocets Recurvirostra avosetta feeding on emerged intertidal areas in a major wintering area, the Tagus estuary (Portugal), was studied during 2 years.Avocets used four different feeding strategies. By far the most common was the Normal Feeding Strategy, in which the median sweeping rate was 28 sweeps per min and the percentage of swallowing movements (ingestions) was very high (median = 90%). No prey were visible in the bill while birds were using this strategy. Another less common feeding strategy was the Worm Feeding Strategy, in which the sweeping rate was higher (median = 46 sweeps/min) and the percentage of swallowing movements was much lower (median = 6%). While using the Worm Feeding Strategy, Avocets preyed on ragworms Nereis diversicolor. The Mixed Feeding Strategy and Scrobicularia plana Siphons Feeding Strategy were rarely observed.In a detailed study on the use of the mudflats by Avocets, it was found that the density of birds on the upper shore was much higher than on the lower shore. There were differences in feeding behaviour between these two areas, although the same feeding strategy was used. On the lower shore, where there was a lower biomass of prey available, sweeping rates were higher and aggressive behaviour did not occur. On the upper shore, sweeping rates were lower and aggressive behaviour was frequent, with some birds defending territories. Nevertheless, estimated food intake rates were 1.5 times higher on the upper shore.
The winter feeding ecology of Avocets Recurvirostra avosetta on intertidal areas. II. Diet and feeding mechanisms
Authors: MOREIRA FRANCISCO 
Published: April 2008

The diet and feeding methods of Avocets Recurvirostra avosetta using the most common feeding strategy (Normal Feeding Strategy) on emerged intertidal areas in the Tagus estuary, Portugal, were studied during two winters.Avocets using the Normal Feeding Strategy fed non‐selectively in the top 20 mm of sediment, ingesting prey bigger than a minimum threshold dimension of around 1.5 mm. Some mud was also ingested whilst feeding. Prey were captured by the mechanical action of the bill, and the estimated number of items captured per sweep was quite high (mean = 10.9 worms). Most of the biomass ingested by Avocets consisted of oligochaetes, spionid worms, Capitella capitata and small ragworms Nereis diversicolor.The estimated intake rate of Avocets suggested that the energy ingested during daylight hours did not represent a significant percentage of the daily requirements. Thus, feeding on emerged intertidal areas is probably a secondary component of their daily gross food intake, unless night feeding yields higher intake rates due to increased prey availability.