bluuebunny/crossref_metadata_2025 huggingface dataset:
Predictors of job satisfaction and absenteeism in two samples of Hong Kong nurses*
Authors: Siu Oi‐ling
Published: March 2003

Background.  Stress‐related outcomes of job satisfaction and absenteeism among nurses should receive more attention in Hong Kong because absenteeism is costly. Many nurses' complaints are due to organizational change in privatization since the establishment of the Hong Kong Hospital Authority in 1991. Organizational climate is found to be an antecedent of job dissatisfaction and absenteeism in many studies in western societies.

Aim.   To investigate the role of organizational climate and psychological distress on job satisfaction; and the role of climate, distress and job satisfaction on absenteeism in Hong Kong nurses, while controlling for demographic variables.

Methods.  A self‐administered questionnaire survey method was used to collect data from two samples of nurses within a 8‐month period. They are, respectively, 144 (74 general nurses, 70 psychiatric nurses; 47 males, 97 females) and 114 (85 general nurses, 29 psychiatric nurses; 17 males, 97 females) nurses.

Results.  Multiple regression analyses revealed that occupational type (psychiatric/general), environment (the physical conditions in the work area) and psychological distress were significant predictors of job satisfaction for sample 1; and well‐being (social relations, welfare and health issues) was the only significant predictor of job satisfaction for sample 2. However, age, involvement (the degree of commitment displayed towards employees by the organization), psychological distress and job satisfaction were significant predictors of absenteeism for sample 1; and occupational type, organization (the interaction between the worker and the organization), and involvement were significant predictors of absenteeism for sample 2.

Conclusions.  The empirical findings provide support for the climate–job satisfaction and climate–absenteeism relationships. Psychological distress could be an antecedent of job satisfaction; and job satisfaction could be an antecedent of absenteeism. Certain climate dimensions should be improved to enhance job satisfaction and reduce distress, which in turn will reduce absenteeism.
Cadets and nursing students: same destination – different route
Authors: Draper Jan , Watson Roger
Published: March 2003

Background.  In response to the policy initiatives in England to secure recruitment and retention in the nursing and midwifery professions, strategies to improve and extend access to preregistration education and training in England have been developed. The relatively recent development of modern cadet schemes is an example of such a strategy. Despite the increasing interest in and proliferation of cadet schemes, there is as yet little evidence for their effectiveness. Reporting on an evaluation of a scheme in England, this paper makes some contribution to this evidence.

Aims and objectives.  The project explored former nurse cadets' experiences of the cadet scheme 9 months after their transition to nurse education. The aims of the project were to evaluate the extent to which former cadets and university staff considered the scheme to prepare students effectively for access to university nurse education.

Methods.  The first cohort of former cadets entered nurse education in September 2000. After 9 months they were invited to contribute to an evaluation of the cadet scheme and their present experience. The evaluation consisted of a structured questionnaire sent to all the former cadets, a focus group interview with the former cadets, informal discussions with university staff and brief documentary analysis.

Conclusion.  Tensions were apparent between the worlds of education and clinical practice: the cadets felt better prepared clinically than academically and found an element of repetition in the nursing programme. They valued their preparation, which they felt put them at an advantage over other nursing students. However, some of them experienced difficulties in the transition to higher education and further review is therefore required to establish the success of cadet schemes.
In the field: notes on observation in qualitative research
Authors: Mulhall Anne
Published: March 2003

Background.  Observation is used in research in two ways – structured and unstructured. Which of these methods to choose depends on the research question but will be defined predominantly by the paradigm underlying each study. Positivistic research generally uses structured observation and interpretist/naturalistic paradigms use unstructured observation. This paper is concerned with unstructured observation.

Aim.  To discuss the importance of unstructured observation as a research method and to examine critically the problems associated with both access and field notes.

Application to nursing.  Although unstructured observation has been used in nursing research, it is less favoured than the interview. Furthermore, although some of the dilemmas concerned with observation such as the role of the researcher, covert research and informed consent have received attention in the nursing literature, other aspects remain relatively unexplored. In particular little has been written concerning access to the field and field notes. Both of these aspects have practical and theoretical considerations that require the attention of the researcher. This omission may partly explain nurses' apparent reluctance to use unstructured observation in their studies. This paper seeks to redress this situation.
Supporting carers of people diagnosed with schizophrenia: evaluating change in nursing practice following training
Authors: Gall Sheena H. , Atkinson Jacqueline , Elliott Lawrence , Johansen Ron
Published: March 2003

Background.  United Kingdom legislation and clinical standards for schizophrenia challenge nurses to re‐examine the support that they provide to carers. Nurses are in a key position to provide this support but may lack the necessary skills to do so. The training programme evaluated in the present study aimed to address this problem.

Study aim.  To evaluate change in clinical practice brought about by post‐registration training for mental health nurses in supporting carers of people diagnosed with schizophrenia.

Design/methods.  The study was undertaken in collaboration between the Universities of Dundee and Glasgow, and Tayside National Health Service (NHS) Trust (Scotland). Respondents were nine nurses who completed training and then delivered a planned programme of support to carers. Data on nursing practice were gathered through semi‐structured interviews with nurses before training and after providing support. Following the support intervention, carers also commented on the nurses' practice.

Findings.  Eight of the nine nurses reported changes in practice in five key areas: They built collaborative relationships with carers, developed a carer focused approach to their practice, acknowledged and supported the carer role, and made progress in identifying carer needs and accessing resources to meet these needs. Nurses experienced difficulties supporting carers who had mental health problems or previous negative experiences of services. Those who lacked community experience also found it difficult to adjust to working in a community setting. Although clinical supervision helped them to work through these difficulties, they remain largely unresolved.

Conclusions.  Findings from this study indicate that appropriate training may enable nurses to improve the support provided to carers of people diagnosed with schizophrenia. This study represents an important stage in determining the nature of support offered to carers by nurses. While developed to help nurses to meet clinical standards set for schizophrenia in the UK, findings may have clinical significance for nurses in other countries.
A positive relationship between local abundance and regional occupancy is almost inevitable (but not all positive relationships are the same)
Authors: HARTLEY STEPHEN
Published: March 2003

Recent attempts to examine the role of different mechanisms in generating a positive abundance‐occupancy relationship failed to properly distinguish between Brown's (1984) sampling artefact, and the form of relationship to be expected from a random distribution of individuals.

Because random distributions generate a positive relationship, one can never predict that removing the influence of some or all of the mechanisms will lead to ‘no relationship’.

In considering how the spatial aggregation of individuals might influence the form of the abundance‐occupancy relationship it is demonstrated that curvilinear and triangular relationships are expected, and that correlation coefficients and linear regression statistics are unlikely to be sensitive to the addition and removal of mechanisms.

Examining distributional data with alternative indices of spatial structure may lead to a more intuitive understanding of how different mechanisms influence the form of abundance‐occupancy relationships.
The adjustment of reproductive threshold to prey abundance in a capital breeder
Authors: Madsen Thomas , Shine Richard
Published: March 2003

1. Many organisms rely upon stored energy reserves to support reproduction and do not initiate breeding until their reserves exceed some ‘reproductive threshold’. However, the determinants of such thresholds are poorly understood; for example, we do not know if they are fixed (invariant) or respond dynamically to fluctuations in resource availability.

2. An 8‐year field study on water pythons (Liasis fuscus Peters 1873) in tropical Australia shows that individual female pythons adjust their reproductive thresholds in response to annual variation in prey abundance.

3. In every year of the study, female pythons that reproduced were in better condition (mass relative to body length) than non‐reproductive females. However, in years with low abundance of rats, female pythons reproduced despite being in relatively poor condition. Indeed, the mean condition of reproductive pythons in one particularly ‘bad’ year was as low as the mean condition of non‐reproductive females in a ‘good’ year.

4. Clutch sizes were slightly reduced in a ‘bad’ year, but the main effect of the lowered threshold was greater emaciation of the females after laying.

5. Recapture records of marked snakes show that the annual variation in thresholds is due to flexibility of individual females, not to differential representation of cohorts with different reproductive thresholds.

6. The dynamic adjustment of threshold levels fits well with predictions from life‐history models and is likely to be a widespread phenomenon.
The foraging performance of great and blue tits (Parus major and P. caeruleus) in relation to caterpillar development, and its consequences for nestling growth and fledging weight
Authors: Naef‐Daenzer Beat , Keller Lukas F.
Published: March 2003

1. We analysed the effect of prey density and size on the foraging performance of great and blue tit (Parus major L., P. caeruleus L.) parents, and its consequences for the growth and fledging weight of nestlings. Because fledging weight is a determinant of subsequent survival and therefore fitness, foraging decisions of the parents play a key role in the reproductive system of tits. The analysis quantifies (i) the rate at which energy is delivered to the nestlings in relation to prey size and abundance, and (ii) the growth rates of nestlings and the resulting fledging weight in relation to the rate of food delivery by the parents.

2. The searching time per prey item increased exponentially with decreasing prey biomass. During the peak abundance of caterpillars, the average searching time per item was 2·5–3 min instead of 5–6 min before and after the peak. Searching time was significantly reduced when the birds returned to the foraging site where the preceding prey was found. This accords with the clumped distribution of caterpillars within the canopy.

3. The foraging performance (in mg caterpillars per min) was maximal when caterpillars were both abundant and large, i.e. shortly before they left the trees for pupation. The high feeding frequency and the large prey then caused a peak energy flow rate to the nestlings of 4–5 times the rate before or after the caterpillar peak. This suggests that the foraging success and rate of food delivery by tit parents was primarily determined by the abundance and size of prey.

4. The growth rate of nestlings, as well as their fledging weight was correlated with the rate of food delivery. Low feeding performance of the parents resulted therefore in poor relative growth rates of only 0·3–0·6 of the rate achieved under optimal conditions and, as a consequence, in a low fledging weight. This indicates that tit parents have restricted options to adjust prey delivery rates according to the requirements of the brood.

5. The results give insight into the chain of causal mechanisms through which an environmental factor (availability of food) has a strong and immediate effect on fitness (growth, fledging weight and, thus, survival of the nestlings). The importance of caterpillar size for foraging success and prey delivery rates of parent tits makes clear, why the phase of best foraging conditions is shorter than the period during which caterpillars are available. The relationships we quantified give a proximate explanation for the great effects that temperature and caterpillar growth have on the between‐year variation in selection intensity for laying date observed in other studies.
Individual variation in the competitive ability of interference‐prone foragers: the relative importance of foraging efficiency and susceptibility to interference
Authors: Caldow R. W. G. , Goss‐Custard J. D. , Stillman R. A. , Durell S. E. A. Le V. Dit , Swinfen R. , Bregnballe T.
Published: March 2003

1.Individual variation in the competitive ability of foraging animals arises from variation in their intrinsic foraging efficiency and in their susceptibility to interference from competitors. Empirical and theoretical studies have concentrated on quantifying the latter and examining its role in determining the distribution and dynamics of animal populations, but have seldom considered the role of variation in foraging efficiency. Using the frequency of occurrence of oystercatchers in supplementary feeding habitats as an index of their competitive ability, we assessed the relative importance of foraging efficiency and susceptibility to interference in determining the overall competitive ability of an individual.

2.Individual mussel‐feeding oystercatchers varied in their tendency to supplement their low‐tide intake by feeding on other prey on upshore tidal flats and in fields. Individuals that opened mussels by stabbing occurred on upshore flats more often than birds which hammered mussels, whereas young birds were more likely to visit the fields than older birds. This difference between habitats emphasized the need to understand the individual differences underlying these class effects.

3.Foraging efficiency increased with age and differed between feeding methods. Dominance also increased with age, but did not differ between feeding methods. An individual's foraging efficiency was not related to its dominance.

4.Individual variation in the usage of either upshore flats or fields, and of each habitat separately, was related to individual variation in foraging efficiency, but not to variation in dominance. Individuals of poor intrinsic foraging ability made greater use of supplementary feeding habitats than did more efficient foragers.

5.Our results show that, even in an interference‐prone system and across a wide range of circumstances, individual variation in foraging efficiency is the major determinant of overall competitive ability. We believe, therefore, that this source of individual variation is of greater importance in determining variation in mortality risk within a population than the effort invested in its study hitherto would suggest. We suggest that a modelling approach is necessary to establish the competitive conditions under which susceptibility to interference might become the more important determinant of competitive ability and, hence, whether such conditions are ever likely to occur in natural populations. We argue that greater emphasis needs to be placed on identifying the determinants of foraging efficiency and its variation between individuals.
Immunocompetence and condition‐dependent sexual advertisement in male house sparrows (Passer domesticus)
Authors: Gonzalez Guillermo , Sorci Gabriele , Møller Anders Pape , Ninni Paola , Haussy Claudy , De Lope Florentino
Published: March 2003

1. We tested the condition‐dependent hypothesis of sexual advertisement in house sparrows (Passer domesticus). Male house sparrows have a bib of black feathers which serves as both a badge of social status and as a cue for female choice. We manipulated environmental conditions during the premoult period of juvenile house sparrows kept in outdoor aviaries. Birds were assigned to two treatments differing in the amount of dietary proteins, which are known to affect the expression of immune response in birds. We tested whether birds in the protein‐rich group had better immune responses and developed larger bibs than birds reared on a protein‐poor diet. We also checked whether immune response was a predictor of survival and parasite resistance.

2. Individuals with higher cellular immune response at capture had greater probability to survive during the 3 months of the experiment, and they had a higher probability to recover from infection withHaemoproteussp. (a blood parasite). Conversely, birds with high immunoglobulin concentrations at capture had a higher probability of mortality.

3. Birds on the protein‐rich diet had a higher cellular immune response compared to birds in the protein‐poor treatment. Humoral immune response showed the opposite pattern, being higher for birds in the protein‐poor treatment. We did not find any effect of food quality on the development of the badge, assessed as the size of the trait and its colour properties.

4. In conclusion, our results support the view that immune defences are important for survival and parasite resistance in natural populations, and that they might be costly to produce. On the other hand, we did not find support for the condition‐dependent hypothesis of sexual advertisement, suggesting that the badge may not be a costly trait to produce. However, badge size could reflect other aspects of condition. The kind of pigments involved in colour signals may be the key factor determining the production costs of such traits.
Long‐term observations on the dynamics of three species of polychaetes living on tidal flats of the Wadden Sea: the role of weather and predator–prey interactions
Authors: Beukema J. J. , Essink K. , Dekker R.
Published: March 2003

1. On the tidal flats of the Wadden Sea, the predatory polychaete Nephtys hombergii (Sav.) is sensitive to low winter temperatures, whereas its main prey, the smaller polychaetes Scoloplos armiger (O.F.M.) and Heteromastus filiformis (Clap.) are not.

2. Monitoring macrofauna dynamics during the last three decades (1970–97) in two distant Wadden Sea areas revealed that Nephtys abundance was severely reduced in all eight coldest winters (generally to an average of < 0·1 g ash‐free dry weight m–2), whereas its biomass reached mean values around 1 g AFDW m–2 during periods with mild winters (≤ 5 days with an air temperature remaining below 0°C all day). Over‐winter changes in Nephtys abundance were strongly related to temperature and 70% of the variability in late winter abundance of this species could be explained by temperature characteristics of the foregoing winter.

3. Biomass values of Nephtys observed in late winter predicted to a high degree (90%) the generally somewhat higher values in the subsequent summer. This seasonal change of predator abundance was generally not related to prey density. Only locally (in an exposed low‐biomass area) and rarely (one‐tenth of the years of observation) did low prey supply (if it was lower than simultaneous predator biomass) coincide with a decline, rather than the usual seasonal increase in Nephtys biomass.

4. A negative influence of predator abundance on prey biomass was observed in both prey species over the entire range of observed predator biomass values. The usual seasonal (winter to summer) increase of prey biomass was significantly smaller at high than at low Nephtys biomass and was even reduced to nil at the highest predator density observed. Scoloplos biomass was about four times higher after years with low (< 0·1 g m–2) than after years with high (> 1·0 g m–2) Nephtys biomass. Similar differences were observed in biomass of Heteromastus.

5. It is concluded that winter temperatures act as an important structuring factor in the Wadden Sea zoobenthic community by directly governing the densities of an important infaunal predator and indirectly affecting the abundance of at least two important prey species. Cold winters intervene by starting a new cycle of predator–prey interaction on average once per 3 or 4 years.

6. Predator abundance was more frequently determined by weather conditions than by food supply. Prey abundance was primarily governed by predator abundance and food supply and was only indirectly (via predator abundance) affected by the incidence of cold winters.
Predicting the relationship between local and regional species richness from a patch occupancy dynamics model
Authors: Hugueny B. , Cornell H.V.
Published: March 2003

1. A linear relationship between the number of species in ecological communities (local richness) and the species pools from which the communities are drawn (regional richness) suggests that species interactions are not sufficient to limit local richness and that communities are not saturated with species. Instead, this relationship implies that communities are open to regional influences and are interlinked by dispersal.

2. Here we show how the linear relationship between local and regional richness in real, noninteractive, assemblages of cynipid gall wasps on California oaks, can be predicted from a simple patch‐occupancy model.

3. One cynipid assemblage has been surveyed for 3 years, allowing for crude estimates of colonization and extinction rates per patch. Using the mainland/island model of patch occupancy dynamics, these rates are combined with the observed number of cynipid species associated with each oak species (regional richness) to predict the expected local species richness in each patch. Assuming that species are independently distributed among localities, the expected variance in species richness among localities is also computed.

4. The model is then tested on an independent data set. When differences in sampling effort (number of surveyed trees per locality) were accounted for, the regression equation relating observed (n = 41) to predicted local species richness does not differ statistically from the line of perfect agreement. The residuals are also distributed according to the predicted variance.

5. Although not statistically significant, the variance in local richness appears to be slightly underestimated by the model. One explanation may be that cynipid species display some positive covariance in their distribution among localities, that is, groups of species occur together in given localities more frequently than would be expected by chance. Variance ratio tests identified statistically positive covariance within cynipid assemblages for three oaks species.

6. The close fit of the model to the data supports the theoretical scenario for noninteractive communities, that the slope of the local–regional richness relationship and patch‐occupancy processes are different expressions of the same phenomenon.
The interactive effects of food and predators on reproduction and overwinter survival of arctic ground squirrels
Authors: Karels Tim J. , Byrom Andrea E. , Boonstra Rudy , Krebs Charles J.
Published: March 2003

1. We examined the effects of food and predators on population limitation in the arctic ground squirrel (Spermophilus parryii plesius Richardson) in the boreal forest of the south‐western Yukon. We focused on ground squirrel reproduction and overwinter survival.

2. Squirrel populations were monitored by live‐trapping and radio‐telemetry from 1993 to the spring of 1996 on four control and four experimental areas (one predator exclosure treatment, two food addition treatments, and one predator exclosure plus food addition treatment).

3. Predator exclusion increased body condition, percentage lactating, percentage weaning litters, litter size, and doubled population density relative to controls, but had no effect on juvenile growth rate, overwinter survival, or juvenile emergence date.

4. Food addition advanced juvenile emergence date and increased adult body condition, percentage lactating, percentage weaning litters, litter size, population density relative to controls (4–7 fold), but had no effect on juvenile growth rate or overwinter survival.

5. Predator exclusion combined with food addition increased adult body condition, percentage lactating, percentage weaning litters, and population density relative to controls (19‐fold).

6. We conclude that arctic ground squirrels in the boreal forest are limited by an interaction between food and predation, acting primarily through changes in reproduction, and that their impact on density was multiplicative.
Increased pre‐natal maternal corticosterone promotes philopatry of offspring in common lizards Lacerta vivipara
Authors: De Fraipont Michelle , Clobert Jean , John Henry , Alder ‐ , Meylan Sandrine
Published: March 2003

1. There is growing evidence that dispersal is highly phenotypically plastic, i.e. that dispersal is condition‐dependent. In the common lizard, dispersal has even been shown to be influenced by the maternal environment during pregnancy. Juveniles in good condition or issued from mothers in good condition disperse earlier or in higher numbers.

2. We hypothesized that plasma corticosterone was the proximate mechanism by which condition and dispersal are linked, and tested this by manipulating the level of circulating corticosterone in pregnant females of the common lizard.

3. After parturition, we measured juvenile attractiveness towards the mother and juvenile dispersal of corticosterone (B) and placebo (P) implanted females.

4. Offspring of B females did disperse in lower number than those of P females. B offspring were also more attracted by the mother's odour than P offspring.

5. In quite a few cases, the behavioural response of juveniles was dependent on the interaction between the hormonal treatment and the mother snout–vent length or condition (body weight corrected for snout–vent length).

6. Corticosterone constitutes therefore one of the proximate mechanisms involved in the prenatal control of juvenile dispersal in this species. Along with other results, it is proposed that prenatal control of dispersal has evolved in order to avoid competition between mothers and their offspring.
Effects of food availability on the distribution of migratory warblers among habitats in Jamaica
Authors: Johnson Matthew D. , Sherry Thomas W.
Published: March 2003

Theoretical arguments suggest that distributions of migratory birds in winter should match patterns of food availability, but in reality the match between migrants and their food may be imperfect because, for various reasons, birds may be unable to ‘track’ food resources. We tested the hypothesis that food availability influences the distribution of migratory canopy‐foraging insectivorous warblers wintering in Jamaica.

Over a wide spatial scale (24 sites on the island), warbler abundance varied significantly among sites and habitats and was significantly dependent on measures of arthropod biomass. Alternative factors (vegetation characteristics, resident bird competitor abundance, predator abundance) were not correlated with warbler abundance.

Over a short temporal scale (about 2 weeks) at a single site, warbler abundance increased as predicted quantitatively after a natural, rapid increase in arthropod biomass.

Over a longer temporal scale (the duration of a winter), changes in density and persistence of individually marked American redstarts (Setophaga ruticilla, L.) on six sites corresponded with concurrent fluctuations in arthropod biomass.

These results document a strong association between arthropod biomass and warbler abundance in time and space, suggesting that warblers wintering in Jamaica distribute themselves in response to food resources.

We hypothesize that dominance hierarchies and variable movement strategies operate in concert with birds’ responses to food to influence the distribution of wintering warblers at different spatial scales. Whether food availability determines habitat quality remains to be investigated.
Phenotypic quality and senescence affect different components of reproductive output in roe deer
Authors: Hewison A. J. M. , Gaillard J. M.
Published: March 2003

Females should adjust their reproductive effort prior to substantial investment. For roe deer, due to delayed implantation, this adjustment may occur at ovulation/fertilization during the summer rut, or at implantation in mid‐winter. We investigated the effects of climate and maternal phenotype (mass, condition, age) on potential litter size (number of fertilized ovulations) and implantation failure (number of fertilized ovulations less number of fetuses) of 818 individual roe does from nine populations across Britain.

Potential litter size varied from 1 to 4, with 0–100% of does per population polyovulating. Among prime‐aged does, 16.7–54.5% subsequently failed to implant at least one blastocyst.

Individual fecundity was determined by the combined effects of maternal phenotypic quality and age, but acting at different stages of the reproductive process: potential litter size increased with increasing maternal body mass; implantation failure was independent of phenotypic quality, but varied in relation to maternal age, being lowest for prime‐aged does, somewhat higher for yearlings, but higher still for senescent females.

Implantation failure increased with increasing initial potential litter size, perhaps related to physiological malfunction. Implantation was often an all‐or‐nothing process, with females either implanting all or failing to implant any of their fertilized blastocysts.

Climatic factors were not consistently correlated with individual female fecundity within populations, but between populations implantation failure increased with climatic severity.

For species such as roe deer, where females rely on food intake rather than fat reserves for reproduction, we suggest that a two‐step process shapes patterns of reproductive output: body mass first sets an upper limit to potential litter size at conception, then reproductive output is limited mainly by senescence and climatic severity through implantation failure.
Evidence for individualistic species assembly creating convergent predator:prey ratios among pond invertebrate communities
Authors: Jeffries Michael J.
Published: March 2003

summary

 Predator : prey ratios are cited as examples of a community level pattern, which suggests underlying assembly rules. Consistent ratios may result from either holistic community interactions or individualistic species assembly. This study tested for evidence of holistic or individualistic explanations for the predator : prey ratios among invertebrate communities of temporary ponds.

 Macroinvertebrate species were recorded from 30 adjacent experimental ponds, in January and early summer over 4 years. After the first 2 years either additional predatory or prey taxa were added to treatment ponds to skew the natural predator : prey ratios. Species richness and ratios were monitored for the following 2 years comparing treatment ponds subject to augmented predator or prey richness against unmanipulated control ponds.

 The majority of species added to treatments established in their respective ponds initially creating unusually high or low predator : prey ratios. In the 2 years following manipulation the ratios in treatment and control ponds converged. The convergence resulted from the spread of the additional species across all the ponds rather than acquisition or extinction of species within treatment ponds compensating for the skewed ratios.

 Convergent predator : prey ratios resulted from the spread of the augmented local species pool across the site rather than holistic community level adjustment within separate ponds. The results support individualistic models of community assembly as the explanation for convergent predator : prey ratios in pond habitats.
Dynamics of common wasps in New Zealand beech forests: a model with density dependence and weather
Authors: Barlow N. D. , Beggs J. R. , Barron M. C.
Published: March 2003

Nest densities of the common wasp ( Vespula vulgaris
(L.)) were monitored at six sites for 13 years in the honeydew‐rich southern beech (
Nothofagus spp.) forests of New Zealand's South Island.

Densities of wasp nests were among the highest in the world, up to 30 ha
−1 , and at any one site varied approximately twofold over the study period.

Strong but not overcompensating density dependence was identified, together with a negative effect of spring rainfall.

The density dependence appeared to act from the number of autumn queens produced during one year to the number of mature (autumn) nests the next year, rather than through variations in queen production per nest. The same stage was also responsible for most of the variability in autumn nest numbers from year to year, with queen production per nest contributing less.

Yearly changes in nest density could be summarized by a simple Ricker model including both density dependence and weather, thereby incorporating both previous hypotheses for the determination of wasp abundance.
Body‐size determinants of niche overlap and intraguild predation within a complex food web
Authors: Woodward Guy , Hildrew Alan G.
Published: March 2003

Body‐size may be an important feature of the structure of food webs. Detailed food web data are however scarce, particularly those including ontogenetic dietary shifts within species. We examined the predator guild in a well characterized food web, that of Broadstone Stream (UK), to assess the importance of body‐size within and among species in relation to intraguild predation and niche overlap.

In agreement with recent food web theory, mutual predation and cannibalism were frequent and occurred in many pairwise permutations. This intraguild predation was strongly asymmetric, being determined by relative body‐size within and among species, and seasonal ‘ontogenetic reversals’ in trophic status arose when generations overlapped.

Predator size determined dietary overlap, with ontogenetic shifts often outweighing taxonomic differences. Small predators had the narrowest diets, regardless of species, and were limited to feeding on a restricted subset of the total prey size‐spectrum. Niche overlap decreased as pairwise differences in body‐size increased among and within species. Overlap in diet also tracked seasonal changes in resource availability, being highest in summer, when prey were abundant and small, and declining progressively over time, as prey became scarcer and/or larger. The small predators also became more detritivorous as prey abundance declined and the larger prey species attained size‐refugia.

The body‐size constraints driving feeding relationships within the predator guild, in terms of both resource partitioning and intraguild predation, lend support to recent niche models of food web structure (Warren 1996;Williams & Martinez 2000). The highly interconnected food web of Broadstone Stream appeared to be structured by relatively simple rules, with seasonal and ontogenetic shifts in the size‐spectrum accounting for most of the changes in predator diet and trophic position. Encounter rate in time (prey and predator mobility) and space (microhabitat use) and foraging mode also influenced prey vulnerability and niche overlap, but were secondary to the effect of body‐size.
Identifying disease reservoirs in complex systems: mountain hares as reservoirs of ticks and louping‐ill virus, pathogens of red grouse
Authors: Laurenson M. K. , Norman R. A. , Gilbert L. , Reid H. W. , Hudson P. J.
Published: March 2003

We examined the role of mountain hares in the louping‐ill virus/Ixodes ricinus tick system to determine whether hares were reservoirs of these pathogens for red grouse. A field experiment, which involved reducing mountain hare densities was undertaken and changes in tick abundance, louping‐ill virus seroprevalence and red grouse densities recorded.

Hares were found to be important hosts for all stages of ticks at two study sites and, where sheep were frequently treated with acaricide, hares fed the greatest proportion of adult ticks. Hare densities were reduced at the experimental site between 1993 and 2001 but remained relatively constant at a control site. Both nymph and larvae tick burdens on red grouse chicks declined over this period to very low levels at the treatment site, but not at the control site. The estimated size of the tick population at the treatment site decreased by more than 99% by 1999.

Louping‐ill prevalence, as measured by antibody prevalence in shot young red grouse, also declined at the treatment site, lagging behind the tick decline by approximately 2 years. The number of young grouse produced per hen grouse at this treatment site increased in comparison to a second control area. However, no change was found in summer grouse densities and thus we cannot demonstrate parasite‐mediated competition.

A deterministic SIR‐type model describing the dynamics of this pathogen/vector/host system was constructed and used to examine the role of mountain hares in louping‐ill virus and tick dynamics. The model predicted a decline in tick numbers and seroprevalence as hare densities reduced. The inclusion of hares as both tick hosts and vector–host–vector transmitters of louping‐ill virus gave the best fit to the observed data.
Comparative nesting and feeding ecology of skylarks Alauda arvensis on arable farmland in southern England with special reference to set‐aside
Authors: Poulsen John Grynderup , Sotherton Nick W. , Aebischer Nicholas J.
Published: March 2003

1.  A study of skylark Alauda arvensis L. breeding ecology in relation to crop type was carried out from April to August 1992 on arable land in southern England. Set‐aside land was included in this comparative study.

2.  Territory density averaged 0·15 ha−1. It was 2–3 times higher in fields of set‐aside and grass, especially permanent pasture, than in winter and spring‐sown cereals.

3.  Territory size was nearly twice as large in fields of winter cereals (4·5 ha) than in other crop types (2·5 ha). Where set‐aside was present on one farm, territory size in set‐aside (1·7 ha) was a third lower than in cereals and grass.

4.  Nesting began in set‐aside and permanent pasture in April and peaked in late May. Nesting was not detected in spring barley until late May and in silage grass until early June. The density of successful nests in set‐aside fields was more than double that in any of the arable crop types.

5.  Average clutch size at hatching was 3·91 eggs in fields of set‐aside, over 15% higher than in silage grass (3·40) and in spring barley (3·27).

6.  Fledging success did not differ according to crop type, but productivity, expressed as the number of fledglings produced per hectare, was 0·50 in set‐aside, 0·13 in silage grass, and 0·21 in spring barley. Nests with chicks were not found in fields of winter cereals. The causes of chick death were thought to be predation in set‐aside fields, farming practices in silage grass fields, and suspected starvation in spring cereals.

7.  The potentially high nesting success of skylarks in set‐aside implies that sympathetic set‐aside management could play an important part in reversing its decline across the European Union.
Recovery of tropical rainforest avifauna in relation to vegetation succession following shifting cultivation in Mizoram, north‐east India
Authors: Raman T.R. Shankar , Rawat G.S. , Johnsingh A.J.T.
Published: March 2003

1.  Recovery of rainforest bird community structure and composition, in relation to forest succession after slash‐and‐burn shifting cultivation or jhum, was studied in Mizoram, north‐east India. Replicate fallow sites abandoned after shifting cultivation 1, 5, 10, 25 and ≈100 years ago, were compared with primary evergreen and semi‐evergreen forest using transect and quadrat sampling.

2.  Vegetation variables such as woody plant species richness, tree density and vertical stratification increased with fallow age in a rapid, non‐linear, asymptotic manner. Principal components analysis of vegetation variables summarized 92·8% of the variation into two axes: PC1 reflecting forest development and woody plant succession (variables such as tree density, woody plant species richness), and PC2 depicting bamboo density, which increased from 1 to 25 years and declined thereafter.

3.  Bird species richness, abundance and diversity, increased rapidly and asymptotically during succession paralleling vegetation recovery as shown by positive correlations with fallow age and PC1 scores of sites. Bamboo density reflected by PC2 had a negative effect on bird species richness and abundance.

4.  The bird community similarity (Morisita index) of sites with primary forest also increased asymptotically with fallow age indicating sequential species turnover during succession. Bird community similarity of sites with primary forest (or between sites) was positively correlated with both physiognomic and floristic similarities with primary forest (or between sites).

5.  The number of bird species in guilds associated with forest development and woody plants (canopy insectivores, frugivores, bark feeders) was correlated with PC1 scores of the sites. Species in other guilds (e. g. granivores, understorey insectivores) appeared to dominate during early and mid‐succession.

6.  The non‐linear relationships imply that fallow periods less than a threshold of 25 years for birds, and about 50–75 years for woody plants, are likely to cause substantial community alteration.

7.  As 5–10‐year rotation periods or jhum cycles prevail in many parts of north‐east India, there is a need to protect and conserve tracts of late‐successional and primary forest.
Long‐term harvesting and male migration in a New Zealand population of Himalayan tahr Hemitragus jemlahicus
Authors: Forsyth David M.
Published: March 2003

1. Sexual differences in behaviour and ecology have important implications for the management of harvested ungulate populations.

2. This study investigated the long‐term effects of harvesting on the abundance and distribution of sexes within an introduced population of Himalayan tahr in the Two Thumb and Sibbald Ranges, New Zealand. Annual counts of tahr were made from 1984 to 1996 in two catchments subject to different harvest regimes.

3. Although populations in the two catchments increased at similar rates over the study period, their adult sex ratios diverged significantly in the late 1980s. In Carneys Creek, which was subject to unrestricted harvest, the adult sex ratio was initially equivalent to the estimated population sex ratio, but from 1991 it was significantly male‐biased. In North Branch, 10 km from Carneys Creek but subject only to adult (trophy) male harvest, the population was significantly female‐biased in all years.

4. There was a large and male‐biased harvest in Carneys Creek in 1993, suggesting that immigration of males may have been responsible for the long‐term changes in sex ratio observed there. In contrast, the harvest of males in North Branch was insufficient to explain its female‐biased population.

5. Monthly counts of male and female tahr in Carneys Creek between December 1993 and February 1996 revealed a consistent seasonal change in the abundance of sub‐adult males, and perhaps adult males, but not females. Sub‐adult males immigrated into Carneys Creek during spring, increasing to a summer maximum before emigrating during autumn; few sub‐adult males were present during winter.

6. Counts at six additional sites during summer and autumn 1996 indicated that the probable source of these males was an adjacent hunting reserve. This hunting reserve, which included North Branch, contained a female‐biased population with moderate female density.

7. The observed changes appear to have been a consequence of sexual differences in habitat selection and mobility. In particular, outside the rut the larger‐bodied males avoided habitats containing high densities of females.

8. Harvesting has the potential to affect the spatial distribution of age–sex classes for sexually dimorphic ungulates. Managers need to consider these effects when designing and interpreting harvest and monitoring programmes.
The use of trapping records to monitor populations of stoats Mustela erminea and weasels M. nivalis: the importance of trapping effort
Authors: Mcdonald Robbie A. , Harris Stephen
Published: March 2003

1. Trapping and hunting records are frequently used as an index of animal abundance. This study demonstrates that these records can be misleading if sampling effort is not controlled for.

2. Mean numbers of stoats Mustela erminea and weasels M. nivalis trapped by British gamekeepers have been decreasing since 1975 and 1961 respectively, giving rise to concern that populations of both species may be declining. However, trapping effort has not been quantified over this period.

3. A total of 203 gamekeepers in England were questioned about the trapping effort they expended and the number of stoats and weasels they trapped in 1997. The most significant factor affecting the number of stoats and weasels trapped was trapping effort.

4. Gamekeepers that relied on hand‐rearing game birds for shooting regarded stoats and weasels as a less serious problem, and made substantially less trapping effort, than gamekeepers that relied on wild game birds.

5. The national decline in the numbers of stoats and weasels trapped may be the result of a decline in stoat and weasel populations. However, the decline is equally consistent with a reduction in trapping effort, corresponding to a national increase in reliance on hand‐rearing game birds for shooting.

6. When the effect of trapping effort was controlled for, the number of weasels trapped by gamekeepers in 1997 was significantly lower in the south‐west than in other regions of England and was unusually low in some local areas.

7. Trapping records can be used effectively to monitor populations of stoats and weasels, as long as gamekeepers record the number of traps set in each month and monthly totals of animals killed. Ideally, the sex of each animal and whether it was trapped or shot should also be recorded. Similar modifications should also be made to other wildlife monitoring schemes based on trapping and hunting records.