bluuebunny/crossref_metadata_2025 huggingface dataset:
Nursing staff and nursing students' attitudes towards HIV‐infected and homosexual HIV‐infected patients in Sweden and the wish to refrain from nursing
Authors: Röndahl Gerd , Innala Sune , Carlsson Marianne
Published: March 2003

röndahl g., innala s. &carlsson m. (2003) Journal of Advanced Nursing 41(5), 454–461

 Nursing staff and nursing students' attitudes towards HIV‐infected and homosexual HIV‐infected patients in Sweden and the wish to refrain from nursing

Background. Two decades after the emergence of human immunodeficiency virus (HIV)/acquired immune deficiency syndrome (AIDS), the infection remains enigmatic and shameful. In Sweden, many HIV‐infected persons still encounter attitudes of avoidance.

Aims. The aims were to investigate differences between attitudes of nurses, assistant nurses, nursing students and assistant nursing students towards HIV‐infected and homosexual HIV‐infected patients; to measure their fear of contracting HIV; and to investigate whether nurses, assistant nurses, nursing students and assistant nursing students wanted to refrain from caring for HIV‐infected patients.

Ethical issues. The participants were informed of the study orally and in writing. Completing and returning the anonymous questionnaires indicated the participants' tacit consent.

Research method. The study had a descriptive, comparative quantitative design. The AIDS Attitude Scale was used, along with a questionnaire specially designed for the study. The participants were nurses and assistant nurses from one infectious disease clinic in central Sweden [response rate was 67% (n  = 57)]. Students enrolled in a university nursing programme and students of upper secondary assistant nurses' training [response rate was 62% (n  = 165)] were also included.

Findings. In general, both the nursing staff and the nursing students expressed empathic attitudes towards HIV‐infected and homosexual HIV‐infected patients, as well as a low degree of fear of HIV contagion. The findings also showed, in the professional groups, that 36% would refrain from caring for HIV‐infected patients if that possibility existed. The corresponding figure for the student groups was 26%.

Limitations. The chosen sample was small and not randomly selected therefore precludes a generalization in a wider context. Furthermore, the questionnaire was untested for reliability and validity, and may have influenced the findings with respect to the wish to refrain from nursing HIV‐infected patients.

Conclusion. Suggested guidelines for nursing, mentor‐ship by AIDS‐dedicated nurses, and educational interventions, are given in ‘Implications for nursing and nursing education’.
Doing practice differently: solution‐focused nursing
Authors: McAllister Margaret
Published: March 2003

Background. Critical thinking and reasoning take many forms; however, a problem‐orientation remains the favoured approach in health care.

Purpose. This paper considers the effects of a problem‐orientation and argues that a solution‐orientation fits nursing's interests more closely and represents an exciting way forward in both education and practice.

Discussion. Whilst a problem‐focus is criticized by some, it remains largely unchallenged as the guiding light for nursing practice. A major reason is that the problem focused approach has strong cultural roots. It is deeply embedded in our thinking, and has become taken‐for‐granted and not often recognized or debated. Whilst problem‐solving has an important place in helping to diagnose disorder and overcome difficulties, nursing needs to move beyond its borders because the role also concerns problem‐free issues such as health and well‐being. Creativity, imagination and focusing on strengths not problems are also important cognitive processes.

Conclusion. A problem‐orientated approach in nursing has had a constraining rather than enabling influence. By refocusing on a solution‐focused approach, we could show how we are different from medicine, and how we aim to do nursing differently through using skills such as engagement, resilience‐building, community development, primary health care and health education.
Quality vs. quantity: energetic and nutritional trade‐offs in parental provisioning strategies
Authors: WRIGHT  , BOTH  , COTTON  , BRYANT
Published: March 2003

1.  When faced with increased brood demand, parent birds provisioning young in the nest can make a variety of adjustments to their foraging and food allocation strategies. Logical extensions of classic optimal foraging theory predict increased provisioning effort to larger broods to be accompanied by changes in load size, foraging distance from the nest, as well as possible changes in the type and size of prey delivered.

2.  We assessed such behavioural adjustments and their consequences in pairs of European starlings (Sturnus vulgaris) responding to a range of experimental brood sizes. Parents feeding larger broods increased their visit rates by spending less time in the nestbox and less time around the nestbox colony. High visit rates to larger broods were also associated with larger loads per visit and changes in the type of prey delivered to the nest. As a consequence, chicks in large and small broods received similar rates of food intake, but experienced differences in the nutritional quality of their food. Parents feeding larger brood sizes were able to increase their provisioning effort despite feeding in the same foraging sites, travelling at comparable flight speeds and maintaining similar body masses to parents feeding smaller broods.

3.  Parental energetic expenditure, measured through doubly labelled water analyses, showed no effect of the brood size treatment. The greater proportion of indigestible material per gram of food delivered to the larger experimental brood sizes (i.e. soil from the guts of earthworms) was probably responsible for the fact that these chicks grew at slower rates and fledged at lower body masses, although we cannot rule out the possibility of lower growth rates due to higher energetic costs of sibling competition within larger broods. Lighter fledglings from large broods disappeared from the local area earlier in the summer, probably as a result of differential mortality rather than premature natal dispersal.

4.  We discuss the adaptive significance of the provisioning trade‐off between quantity and quality of food items delivered by parents to the nest, with reference to natural variation in foraging conditions and brood demand.
Ontogenetic influences on foraging and mass accumulation by big brown bats (Eptesicus fuscus)
Authors: HAMILTON IAN M. , BARCLAY ROBERT M.R.
Published: March 2003

Juvenile flying animals, including bats, often cease increasing, or even decrease in body mass after the onset of flight. The low body mass of juvenile bats may be a result of stresses associated with the initiation of flight, or may be an adaptation to reduce flight costs.

To test these hypotheses, the body masses of adults and unknown aged juvenile big brown bats (Eptesicus fuscus) were separately compared in August 1990 through to 1995. It was hypothesized that there should be little variation in the body mass of juveniles from year to year if low body mass is an adaption to reduce flight costs.

The foraging behaviour and body masses of bats of known or estimated age were also compared in 1994 and 1995. Ambient temperature at sunset was greater in 1994 than in 1995. It was assumed that prey density and predictability increased with temperature, and hypothesized that if low body mass results from energetic stress, then this should be more apparent in 1995. Using radiotelemetry, the foraging behaviour of juvenile, yearling and adultE. fuscuswas compared in 1994 and 1995 to determine whether young bats attempt to compensate for energetic shortfalls by foraging for longer, or emerging earlier, than adults.

Unknown‐aged juveniles did not differ significantly in body mass in August from 1990 through to 1995. Adults were significantly heavier in August in 1990 and 1994 than in 1991, 1993 and 1995. Known‐aged juveniles had lower body mass than adults in 1994, and lower wing loading than adults in 1995. Known‐aged juveniles did not differ in mass between 1994 and 1995, while adults were heavier in 1994.

The foraging times for juvenile and adult bats were both significantly related to ambient temperature. However, the slope of this relationship was steeper for weaned juveniles than for adults. The foraging times of yearling and adults bats were not significantly different.

The emergence times of juvenile and adult bats did not differ, nor did the emergence times of yearlings and adults. Emergence time did not differ significantly between 1994 and 1995.

The results of the study suggest that juvenile bats maintain a low body mass even under conditions that permit adults to accumulate greater fat deposits. Juveniles do not forage earlier or for longer to compensate for poor foraging ability and increased energy expenditures resulting from the onset of flight. This suggests that, by maintaining a low body mass, juveniles reduce flight costs and the risk of predation at a time when flight and foraging are still developing.
Cohort variation in male survival and lifetime breeding success in red deer
Authors: ROSE K.E. , CLUTTON‐BROCK T.H. , GUINNESS F.E.
Published: March 2003

We investigated cohort differences in the lifetime breeding success and survival of male red deer Cervus elaphus L. in an increasing population on the Isle of Rum, Scotland.

There were significant differences in survival through different stages of the life span between 15 cohorts of males, ranging between: 0.26–1.00, calf survival through first winter; 0.56–1.00, yearling survival; 0.44–0.94, adult survival. This variation in survival was related to environmental conditions in the cohorts' year of birth, whilst controlling for annual effects.

For 10 cohorts of males with complete lifetime data, mean breeding success also varied significantly, between 0.83 and 3.86. This variation, too, was associated with environmental conditions in the cohorts' year of birth.

Since in many sexually dimorphic mammals, the growth and survival of males is more strongly affected by adverse environmental conditions than that of females, we expected that cohort variation would be more extreme amongst males than females. This was true, for both cohort survival and reproduction.

We expected to observe selection on cohort adult body size, related to survival or reproduction. However, there was no evidence of variation in adult body size between cohorts, nor for relationships between differences in body size between cohorts and measures of survival or breeding success. Cohorts which underwent high intial mortality subsequently experienced higher adult survival than cohorts not subjected to high density‐related selection early in life.
Scale‐dependent correlations between the abundance of Brünnich's guillemots and their prey
Authors: Mehlum Fridtjof , JR George L. Hunt , Klusek Zygmunt , Decker Mary Beth
Published: March 2003

1. The foraging ecology of Brünnich's guillemots Uria lomvia was studied during the breeding season in south‐eastern Svalbard. In the region of Storfjorden there are two large breeding colonies comprising a total of about 540 000 individuals. These birds forage in the western part of Storfjorden and further to the south. Their main prey are polar cod Boreogadus saida, pelagic amphipods Parathemisto spp. and euphausiids Thysanoessa inermis.

2. A ship‐based transect survey was used to record bird abundance and the acoustically determined biomass of presumed prey. The five transects were divided into 33 segments, each 8–11 km in length. The resolution of the survey was 150 m, and analyses of correlations between predators and prey were performed at length scales from 150 m to 9 km. We differentiated acoustic signals into aggregated and dispersed categories according to the estimated horizontal distribution of presumed prey.

3. Foraging guillemots were consistently more strongly correlated with the aggregated prey than with dispersed prey over scales ranging from 150 m to 9 km. Correlations were weak at small scales (150 m – 1 km) and increased and stabilized at scales of 2–3 km. The spatial scale at which we obtained a shift from weak to strong correlations between guillemots and their prey was similar to the scale at which the spatial variances in both guillemot and prey abundance were high.

4. Guillemots showed low correlations with prey at low prey densities. Similarly, correlations between guillemots and prey were low at low bird densities. The data support the hypothesis that the birds associate with prey patches with densities above a certain threshold, and that ‘regional’ prey abundances affect local use of patches.

5. The numerical aggregative response curves between guillemot and prey density were classified as being neither hyperbolic (type II) or sigmoidal (type III) within the range of prey densities observed in this study. The aggregative response curves were sensitive to spatial scales, which suggest that studies of response curves should be conducted at a range of spatial scales.
Prey abundance and the strength of interference in a foraging shorebird
Authors: Triplet Patrick , Stillman Richard A. , Goss‐Custard John D.
Published: March 2003

Interference is an important component of food competition but is often difficult to detect and measure in natural animal populations. Although interference has been shown to occur between oystercatchersHaematopus ostralegusL. feeding on musselsMytilus edulisL., four previous studies have not detected interference between oystercatchers feeding on cocklesCerastoderma eduleL. In contrast, this study detected interference between cockle‐feeding oystercatchers in the Baie de Somme, France. Prey stealing (kleptoparasitism), one of the main causes of interference between mussel‐feeders, also occurred between oystercatchers in the Baie de Somme. The kleptoparasitism rate was related to the natural variation in the food supply, tending to be higher when cockles were rare. Feeding rate was negatively related to competitor density, so providing evidence for interference, but, as in mussel‐feeders, only above a threshold density of about 50–100 birds ha−1. The strength of interference at a fixed competitor density was related to the cockle food supply, usually being greater when cockles were rare. Previous studies probably failed to detect interference between cockle‐feeders because competitor densities were too low, or cockles were too abundant, or because they were not conducted during late winter when interference is most intense. The study shows that natural variation in the food supply can influence the strength of interference within an animal population and provides support for those behaviour‐based interference models which predict that the strength of interference will be greatest when competitor densities are high and prey scarce.
The taxonomic distinctness of coastal bottom‐dwelling fish communities of the North‐east Atlantic
Authors: Rogers Stuart I. , Clarke K. Robert , Reynolds John D.
Published: March 2003

1. New techniques for identifying the average taxonomic range of species assemblages were applied to an extensive dataset of bottom‐dwelling fish in the coastal waters of NW Europe. These taxonomic distinctness indices provided much greater resolution than traditional diversity indices as they incorporated information on taxonomic relationships into an index which measures species dominance. Unlike standard measures of species richness and diversity, the mean value of these statistics is independent of sampling effort, and this allows objective comparisons to be made between samples from studies where sampling effort is not standardized.

2. A reduction in the average taxonomic range between the fauna of western waters of the UK and that of the southern North Sea was consistent with the general decline in species richness observed between these regions, and suggests that these two factors may be spatially positively correlated. Indices calculated for individual samples of fish on a local scale, however, did not all fit this trend.

3. Much of the variability in taxonomic diversity within the coastal waters of NW Europe was caused by the variable geographical distribution of the elasmobranchs. Of all the families which comprise the fish communities, this group has life‐history characteristics which make it most susceptible to impact by commercial trawl fisheries.

4. The use of taxonomic distinctness measures provided additional insights, of relevance to biodiversity assessment, suggesting that they might usefully be applied to other aquatic and terrestrial fauna.
The functional and aggregative responses of a herbivore: underlying mechanisms and the spatial implications for plant depletion
Authors: Rowcliffe J. Marcus , Sutherland William J. , Watkinson Andrew R.
Published: March 2003

1. The functional and aggregative responses of dark‐bellied brent geese Branta bernicla bernicla feeding on the green algae Enteromorpha intestinalis and Ulva lactuca are described.

2. Bite rate showed maxima at both high and low algal biomass, although the functional response in terms of biomass intake rate was linear (type‐1). The differences in the shapes of these responses can be explained by the fact that bite size declines with decreasing algal biomass.

3. There was little interference between the geese; the rate of aggression was only weakly related to goose density, and time spent feeding decreased only slightly with increasing density.

4. Geese fed on all parts of the algal bed, showing weak, but significant aggregation in patches of higher algal biomass in both October and November.

5. The observed pattern of aggregation was weaker than that predicted by the ideal free distribution with a low value of interference.

6. Simulation models were used to explore four possible behavioural factors leading to this deviation from predictions: cost of travel between patches, constraints on the perception of patch quality, disturbance and short‐term resource guarding. It is concluded that resource‐guarding is likely to be the most important contributory factor.
Determinants of geographical range sizes: a test using introduced New Zealand birds
Authors: Duncan Richard P. , Blackburn Tim M. , Veltman Clare J.
Published: March 2003

1. The 34 species of birds that have been successfully introduced to New Zealand offer a unique opportunity to study patterns of variation in geographical range sizes, and to test mechanisms that may be responsible for that variation, because the New Zealand range sizes have established within the last 160 years and because there are data on the starting conditions, including the year of first recorded release and the subsequent effort put into the introduction of each species.

2. We collated data on geographical range sizes, life history traits, dates of introduction and initial introduction effort for the birds successfully introduced to New Zealand. To test whether range size–life history correlations show a consistent pattern between regions, we collated further data on geographical range sizes and life history traits for British breeding birds.

3. The geographical range sizes of birds introduced to New Zealand did not depend on the length of time since they were introduced. Instead, large geographical ranges were exhibited by species whose preferred habitat is widespread in New Zealand, species with life history traits associated with higher rates of population growth (high fecundity, fast development and small body size), species that are partial migrants in part of their natural range, and species that were initially introduced more often and in greater numbers to New Zealand.

4. The strength and direction of geographical range size–life history correlations in introduced New Zealand and British breeding birds were very similar. There was also a strong positive correlation between the geographical range sizes of the species introduced to New Zealand from Britain and their geographical range sizes in Britain. However, the similarity of the correlations between life history traits and geographical range sizes in both regions was not a simple consequence of this; the similarity persisted when species introduced from Britain were excluded from the New Zealand data.

5. We discuss the implications of these results for understanding variation in geographical range sizes in the introduced New Zealand avifauna.
Food regulates the Serengeti wildebeest: a 40‐year record
Authors: Mduma Simon A. R. , Sinclair A. R. E. , Hilborn Ray
Published: March 2003

1. The migratory wildebeest (Connochaetes taurinus (Burchell)) population of Serengeti has been monitored for 40 years (1958–1998). The population increased from 1963 to 1977, stabilized from 1977 to 1993 and declined during drought in 1993–94. These changes provided a significant contrast in densities and the opportunity to determine the life history stages where survival was density dependent and their causes.

2. There was a delay in age of maturity and a decline of both yearling and adult pregnancy rates at higher densities. Changes in yearling pregnancy had minimal effect on number of calves born. Adult pregnancy rate dropped from 95% to 88%

3. The greatest absolute mortality occurred in newborn calves (0–4 months old). The most variable survival was in dry‐season calf mortality (5–11 months old).

4. Density dependence was clearly present in adult mortality and this appeared to be the regulating life stage. Density dependence was also found in dry‐season calf mortality. The drop in pregnancy rate was only weakly density dependent.

5. The main cause of mortality (75% of cases) was undernutrition. Bone marrow condition showed that more animals died in extremely poor condition as the population increased and predators did not cause these deaths.

6. Predation played only a minor role in limiting the wildebeest population. Predators caught animals in moderate condition during the increase phase and increasingly healthy condition during years of high population density. The main predators were lion [Panthera leo (Linnaeus)] and hyaena (Crocuta crocuta Erxleben).

7. Adult mortality was significantly negatively related to food per capita. This could be viewed either as curvilinear density dependence, or as two phases of mortality. The first phase was during population increase when mortality was inversely density dependent and may have been caused by a constant predation rate. The second was during stability and decline and comprised the additive effects of undernutrition and predation.

8. Rainfall in the dry season was the most important extrinsic determinant of food supply for the wildebeest population but food was related to mortality only when population density was incorporated.

9. At present the wildebeest population appears regulated by natural causes through food supply. Human‐caused mortality appears to be a minor factor. However, if the number of wildebeest killed by humans increases as human population increases, then there could be a permanent decline in wildebeest, and a major change in the whole ecosystem, because wildebeest are the keystone species. Continued monitoring is essential for conservation of the Serengeti ecosystem.
Hatching asynchrony in the Eurasian kestrel Falco tinnunculus: an experimental test of the brood reduction hypothesis
Authors: Wiehn Jürgen , Ilmonen Petteri , Korpimäki Erkki , Pahkala Maarit , Wiebe Karen L.
Published: March 2003

1. We tested the brood reduction hypothesis by manipulating hatching spans of Eurasian kestrel Falco tinnunculus (Linnaeus) broods during two low vole years (1996–97) in western Finland. In addition, half the broods in 1997 were food supplemented during the entire nestling period.

2. Nestling mortality was high, occurring in 55% of nests, and the effect of manipulated hatching span on fledging success was more pronounced than either the effects of year or supplementary food. In contrast to the predictions tested, fledging success was higher in synchronous than asynchronous nests, both when food was limiting and when food conditions were substantially improved by food supplements.

3. We found no evidence that brood reduction resulted in higher quality (body mass) of surviving young in low vole years. On average, fledglings were heavier at synchronous than asynchronous nests. This was only the case, however, when food was limiting.

4. Most nestling mortality occurred when the chicks were 2 weeks old, and age of death did not differ between the brood types. Parents at synchronous nests fed their broods at a higher rate than at asynchronous broods, this divergence arising only in the latter part of nestling period.

5. This is the first hatching span experiment where synchronous hatching seemed more profitable than asynchronous during conditions of both food scarcity and food abundance. The higher parental workload at synchronous nests could, however, counterbalance the benefits of synchronous hatching.

6. Hatching in natural broods of Eurasian kestrel is more synchronous in low vole years compared to high vole years. The fact that synchronous broods out‐performed asynchronous broods in both ‘low’ years of the study is consistent with the facultative manipulations. The benefit of asynchrony in high vole years is still unclear.
Eggload dynamics and oviposition rate in a wild population of a parasitic wasp
Authors: Casas Jérôme , Nisbet Roger M. , Swarbrick Sue , Murdoch William W.
Published: March 2003

1. This paper develops and tests in the field a model that predicts the oviposition rate and the rate of egg maturation of a synovigenic parasitic wasp during a foraging period. The parasitoid is Aphytis melinus, the highly successful biological control agent of California redscale (Aondiniella aurantii), a pest of citrus worldwide.

2. Females were sampled in the interior canopy of grapefruit trees either just before and at the end of the foraging period over 2 days and were dissected to determine the starting and ending eggload distributions. A group of females was caught before the onset of activity and kept in vials in the field in trees with honey but without access to hosts during the foraging period. Their eggload at the end of the day was used to estimate the egg maturation rate during the foraging period.

3. Two stochastic models are used to predict the eggload distribution at the end of the day. Both use the observed starting eggload distribution, the observed length of the foraging period and the estimated rate of egg maturation. The model providing the better fit uses an oviposition rate which is an increasing function of the eggload.

4. The eggload does not attain a steady state distribution during a foraging period. One‐third to one‐half of the population is predicted to experience egg‐limitation at some time during the foraging period. Five percent of the population will experience egg‐limitation a second time within a single day.

5. The common occurrence of egg‐limitation over a single day and the relatively high rate of change of states between egg‐ and time‐limitation imply that the rate of nutrient acquisition and use are likely to be subject to strong evolutionary pressures.
Geometric scaling of microhabitat patches and their efficacy as refugia during disturbance
Authors: Lancaster Jill
Published: March 2003

1. A field experiment was carried out to determine whether the accumulation of stream invertebrates in refugium patches during high flow disturbances was influenced by the geometric scaling of the patches, i.e. edge to size relationships.

2. Flow was reduced experimentally by creating artificial flow refugia and comparing invertebrate colonization of refugium and control patches. There were eight sizes of colonization cage (1·5 cm mesh) with surface area/volume quotients (SA/V) which ranged from 1·2 to 0·5. Control cages were open to the flow; artificial refugia were baffled upstream by 0·3 cm mesh to reduce flow. Four, week‐long experimental trials were carried out during the winter months in an upland Scottish stream. On two occasions, discharge was high, on two it was low.

3. The results are consistent with the hypothesis that stream invertebrates accumulate in refugia during high flow disturbances. The density of colonists was higher in refugia than control cages after high discharge for some taxa. There was no difference between treatments for any taxon at low discharge.

4. The shape of soft‐edged microhabitat patches appears to be important in mediating the impact of disturbance in streams. Small refugium patches (high edge to size ratio) appeared to be more efficacious than large patches for taxa that accumulate in refugia during disturbances. Density increased with SA/V in all trials and for all taxa, but the slopes of the lines relating density to SA/V differed between control and refugium patches after disturbance for some taxa.

5. According to trait‐based analysis, taxa that have high mobility or that are vulnerable to high hydraulic forces may be especially dependent upon small flow refugia to maintain population size. Whether movement is by active or passive means is less important.
Individual variation in intake rate: the relative importance of foraging efficiency and dominance
Authors: Stillman R. A. , Caldow R. W. G. , Goss‐Custard J. D. , Alexander M. J.
Published: March 2003

1.Individual variation in the intake rate of foraging animals arises largely from variation in two characteristics: their intrinsic ability to forage in the absence of competitors (foraging efficiency) and the detrimental effect of competitors on their intake rate (susceptibility to interference). We use a model to explore the relative importance of foraging efficiency and dominance, which influences susceptibility to interference, in determining the intake rate of foraging animals at a range of competitor densities.

2.The model is parameterized and tested for a shorebird–prey system, oystercatchersHaematopus ostralegusL. feeding on musselsMytilus edulisL., in which interference occurs because dominant individuals steal prey from subdominant ones. In both oystercatchers which open mussels by stabbing their bill between the shell valves (stabbers) and those which hammer a hole through the shell (hammerers), foraging efficiency is predicted to be the major determinant of intake rate at competitor densities below 100–150 birds ha‐1and dominance the major determinant at higher densities. In reality, a very similar relationship is found in stabbers, but in hammerers foraging efficiency remains the most important determinant of intake rate across the full range of observed competitor densities, in contrast to the model's prediction. Oystercatchers typically forage at densities in the range 100–250 birds ha‐1, in the region in which foraging efficiency and dominance are of approximately equal importance to stabbers, while foraging efficiency is most important to hammerers. We suggest reasons for the difference in the model's predictive power for stabbers and hammerers.

3.We use the model to make the general predictions that the relative importance of foraging efficiency is higher when (i) it varies more between individuals, (ii) prey encounter rate is high, (iii) handling time is short, (iv) prey stealing (kleptoparasitic) attacks occur over short distances, (v) the probability of stealing prey is low, and (vi) movement speed while foraging is low. In the oystercatcher–mussel system, prey encounter rate is lower and handling time longer than in most other shorebird–prey systems. This suggests that the importance of foraging efficiency in determining intake rate is likely to be greater in many other shorebirds.

4.Most studies of between individual variation in intake rate have focused on the importance of dominance rather than variation in foraging efficiency. Both the model predictions and field data suggest that variation in foraging efficiency may be a more important source of variation in intake rate than its previous depth of study would suggest.
Aphid suitability and its relationship to oviposition preference in predatory hoverflies
Authors: Sadeghi Hussein , Gilbert Francis
Published: March 2003

1. The fitness consequences of feeding on different aphids (apple, blackberry, dock, elder, nettle, pea, rose and sycamore aphids) for two species of generalist insect predator (the aphidophagous larvae of Episyrphus balteatus and Syrphus ribesii— Diptera:Syrphidae) were measured in the laboratory. The relevant literature studies on prey specialization in the Syrphidae were summarized for the first time.

2. Both the literature evidence reviewed and the data from the experiment indicated that fitness components and overall individual fitnesses are broadly similar among all aphid species, with some exceptions.

3. We correlated individual fitness to two estimates of oviposition preference, an indirect (field distribution of larvae) and a direct measure (egg distribution under laboratory conditions). In the non‐resident, migratory E. balteatus significant correlations were absent, but there were indications of a weak preference‐performance correlation in the largely resident S. ribesii.
Factors affecting breeding dispersal in the facultatively colonial lesser kestrel: individual experience vs. conspecific cues
Authors: Serrano David , Tella José L. , Forero Manuela G. , Donázar José A.
Published: March 2003

The role of individual experience vs. the use of conspecific cues on breeding dispersal decisions have seldom been determined in colonial birds. We studied causes of breeding dispersal in the lesser kestrel (Falco naumanni), a species that breeds in colonies of variable size as well as solitarily. During a 6‐year study in Spain, we gathered information on 486 subsequent breeding attempts and on 26 explanatory variables which evaluated individual experience, conspecific cues in terms of breeding performance and colony size, and different ecological and populational characteristics.

Two decisions were separately analysed: whether or not to disperse, and how far to move. Generalized Linear Mixed Models (GLMMs) allowed us to identify the relative contribution of each explanatory variable while controlling for the non‐independence of individual dispersal decisions across years.

Females seemed to disperse more often than males (34% vs. 19%), and both sexes apparently dispersed less with age. However, a GLMM showed that experience (i.e. the number of years a bird bred in a particular colony) was the only factor influencing breeding dispersal. Birds showed higher site fidelity the greater their experience in a colony, which could be related to benefits derived of increased local familiarity. A second GLMM showed that, before birds acquired experience in a particular colony, individual nest failure due to predation and proximity to other colonies increased the probability of dispersal, dispersal being also higher in colonies with poor conspecific breeding success. Furthermore, solitary nesting birds were more prone to disperse and dispersal probability decreased the larger the colony of origin, according to fitness expectations associated with colony size.

A GLMM explaining dispersal distances retained two variables – birds dispersed farther the lower the breeding density in the surroundings, and the larger the distance to the nearest colony. Dispersing birds tended to settle within their previous foraging areas (median dispersal distance = 1·6 km), being constrained by the availability of nearby colonies.

Lesser kestrels mainly cue on their own breeding performance and experience in a particular colony at the time of taking a dispersal decision. However, inexperienced birds also partially cue on the size and breeding success of their own colonies (but not on the size or breeding performance of other colonies), and birds moved larger distances when dispersing from areas of low populational density. These results support some degree of conspecific attraction.
Spatio‐temporal patterns of mink and muskrat in Canada during a quarter century
Authors: Viljugrein Hildegunn , Lingjærde Ole CHR. , Stenseth Nils CHR. , Boyce Mark S.
Published: March 2003

Fur‐return data on muskrat (Ondatra zibethicus) and mink (Mustela vison) from 80 posts of the Hudson’s Bay Company were analysed. From each post we obtained the number of furs bought from trappers during 25 years (1925–49).

 The ecological information content of the data was assessed using questionnaires sent to each post. We conclude that fur‐return data reflect relative abundance of muskrat and mink, and not primarily information about the trappers.

 The most‐common temporal pattern of the two species are cycles with a period of 8–9 years, with muskrat cycling 1–2 years ahead of the mink. This pattern, as would be expected in a typical predator–prey relationship, is found throughout the boreal forest region, with the exception of several posts in eastern Canada. In the eastern region, the two species were found to fluctuate in synchrony.

 The data show broad‐scale synchrony. Peaks (and troughs) are roughly aligned in phase over the entire Canadian boreal forest.

 In some areas the phase of the cycle is either ahead or behind the average cycle. Peaks (and troughs) of mink and muskrat cycles generally appear first in the Athabasca Basin region (for mink in the Hudson’s Bay region of Manitoba and Ontario) and from this epicentre spread throughout Canada within 2–3 years.

 Synchrony (i.e. mean correlation) declines with distance; for distances less than 450 km, similarity among populations is higher than the average.
Migratory and sedentary blackcaps in sympatric non‐breeding grounds: implications for the evolution of avian migration
Authors: Pérez‐Tris Javier , Tellería José Luis
Published: March 2003

Several hypotheses have attempted to explain why sedentary populations persist in the wintering grounds of many migratory bird species. For instance, residents may overcome the flooding of their range if they are better competitors than migrants. Alternatively, each population fraction may use different resources or even different habitat types, for example because residents benefit from site tenacity while migrants benefit from resource tracking.

To evaluate these hypotheses, we studied the distribution of sympatric migratory and sedentary blackcaps (Sylvia atricapilla) in southern Spain during two winters. We distinguished two habitat types: forests, which are used by residents for breeding, and shrublands, to which blackcaps spread in winter with the arrival of migrants. Shrublands are unsheltered habitats that show more abundant but less diverse fruits than forests. We investigated (i) if blackcaps show habitat segregation with respect to migratory behaviour, sex, age and body size, (ii) what resources are used by each population fraction within each habitat type and (iii) how habitat occupancy affects the body condition of individuals.

Residents were almost completely restricted to forests, while migrants occupied both habitat types. Among migrants, adults predominated in forests and juveniles in shrublands, but no sexual segregation was found. Body size was larger in residents than in migrants, and these were larger in forests than in shrublands (especially juveniles). If larger birds are dominant, these results support the idea that residents may endure in forests and exclude the most subordinate migrants (juveniles and small birds) towards shrublands.

Within forests, migrants and residents tracked fruit abundance, but residents were also associated with the most suitable breeding sites. Migrants tracked fruits less closely in shrublands, due probably to a higher fruit abundance and a lower availability of shelter.

Habitat segregation did not affect muscular development of migrants. However, migrants accumulated more fat in shrublands. Therefore, differences in nutritional quality cannot explain why adult and larger blackcaps predominate in forests. Instead, other factors such as food diversity or exposure to predators might account for this distribution.

Our results provide a mechanism to explain the persistence of sedentary populations despite migrants overflowing their range and using the same resources. Residents may challenge the arrival of conspecifics because they are better competitors. From an evolutionary perspective, this shows that non‐breeding processes may be as important as breeding benefits accrued to migrants for explaining the dynamics of migratory and sedentary populations.
Movement parameters of ungulates and scale‐specific responses to the environment
Authors: Johnson Chris J. , Parker Katherine L. , Heard Douglas C. , Gillingham Michael P.
Published: March 2003

Most studies of animal movements and habitat selection do not recognize empirically that different components of the environment are important to animals at different scales. Often, availability of habitats is defined at one or more arbitrary spatio‐temporal scales, but use of those habitats is constrained to one scale. Identification of scalar movement is the first step in developing models to explain why animals select or move to certain parts of their range. We used a non‐linear curve‐fitting model of movement rates to identify discontinuities in the scales of movement by woodland caribou Rangifer tarandus caribou collared with global positioning system (GPS) collars.

We differentiated intrapatch from interpatch movements, but were unable to distinguish interpatch from migratory‐type movements for most combinations of individual caribou by season. Model fit was stronger for winter than summer movements. We suggest that increased patch heterogeneity during the winter resulted in interseason variation in movements and corresponding model fit.

Responses by caribou to the environment were scale‐dependent. When we applied logistic regressions, land‐cover type, energetic costs of movement, and predation risk differentiated the two scales of movement. Intrapatch movements had a lower cost of movement, were associated with cover types where foraging behaviours probably occurred, and were closer to areas of higher predator risk than interpatch movements.

Application of the non‐linear model will aid in developing mechanism‐based approaches to studying resource selection and animal behaviour.
Spatial patterns of population regulation in sage grouse (Centrocercusspp.) population viability analysis
Authors: LaMontagne Jalene M. , Irvine Robyn L. , Crone Elizabeth E.
Published: March 2003

Population viability analyses (PVAs) are commonly used to identify species of concern. Many PVA techniques assume that all populations are regulated by a single mechanism.

We compared population viability predictions for three subspecies of sage grouse (Centrocercusspp.) based on the assumptions that: (i) population regulation was density‐independent vs. dependent on more complex feedback mechanisms; (ii) the mechanism of population regulation was homogeneous within a region vs. heterogeneous among leks; (iii) environmental variation was spatially correlated within regions vs. uncorrelated among leks.

We used sage grouse as a model species for this analysis because counts of lekking male grouse are available in some areas since the 1950s, these counts are known to fluctuate widely, and sage grouse appear to be declining throughout their range.

We fit population regulation models to data including density‐independence, density‐dependence, delayed density‐dependence and a simplified version of Turchin & Taylor's (1992) response surface model.

We show that the best‐fit models typically include spatial heterogeneity in mechanisms of population regulation. Inclusion of spatial heterogeneity increased expected time for population persistence, and changed the rank order of risk of extinction for different regions.

We suggest that it is important to consider multiple models of population regulation when applying population viability analysis techniques because viability projections are influenced strongly by model structure.
Role of forage, habitat and predation in the behavioural plasticity of a small African antelope
Authors: Brashares Justin S. , Arcese Peter
Published: March 2003

Ecological influences on social organization can best be measured by comparing populations of a socially variable species living in different environments. We examined causes of variability in social behaviour in a socially plastic small antelope, the oribi,Ourebia ourebiZimmermann, in Ghana, West Africa.

In total, 161 individually identified oribi were observed at five sites along an ecological gradient through dry and rainy seasons. Behavioural observations and ecological data were used to test the relative influence of forage abundance and quality, habitat structure and predation pressure on female dispersion and male social behaviour.

Of nine ecological variables that were quantified, forage abundance and quality accounted best for variation in female dispersion among and within study populations. Specifically, female oribi formed larger groups and had smaller ranges where dry season forage was relatively abundant and low in fibre.

Male territorial behaviour differed among sites and was related to female home range size. Males were most active in territory maintenance where females had small home ranges, and males defended a female rather than a territory where females ranged widely.

These results show that variation in social organization among oribi subpopulations in Ghana reflects female responses to the availability and quality of dry season food resources and male responses to the variable distribution and ranging behaviour of females.
The importance of host spatial distribution for parasite specialization and speciation: a comparative study of bird fleas (Siphonaptera: Ceratophyllidae)
Authors: Tripet Frédéric , Christe Philippe , Møller Anders Pape
Published: March 2003

The environment of parasites is determined largely by their hosts. Variation in host quality, abundance and spatial distribution affects the balance between selection within hosts and gene flow between hosts, and this should determine the evolution of a parasite's host‐range and its propensity to locally adapt and speciate.

We investigated the relationship between host spatial distribution and (1) parasite host range, (2) parasite mobility and (3) parasite geographical range, in a comparative study of a major group of avian ectoparasites, the birds fleas belonging to the Ceratophyllidae (Siphonaptera).

Flea species parasitizing colonial birds had narrower host ranges than those infesting territorial nesters or birds with an intermediate level of nest aggregation.

The potential mobility and geographical ranges of fleas decreased with increasing level of aggregation of their hosts and increased with the fleas’ host ranges.

Birds with aggregated nest distribution harboured more flea species mainly due to a larger number of specialists than solitarily nesting hosts.

These results emphasize the importance of host spatial distribution for the evolution of specialization, and for local adaptation and speciation in Ceratophyllid bird fleas.