bluuebunny/crossref_metadata_2025_split huggingface dataset:
Population dynamics of the Mongolian gazelle Procapra gutturosa: an historical analysis
Authors: Milner‐Gulland E.J. , Lhagvasuren Badamjavin 
Published: March 2003

1.  The Mongolian gazelle Procapra guttorosa is legally hunted, but has no scientifically‐based management strategy. It has suffered a range contraction in recent years, but the reasons for this are unclear. This paper addresses both of these issues. 2.  The available data on the population dynamics and human influences on the Mongolian gazelle are presented and evaluated. Districts which currently contain Mongolian gazelles had a significantly lower human population density in 1969 than those which no longer contain gazelles. 3.  A discrete‐time age‐ and sex‐structured model is developed for the Mongolian gazelle. The model includes stochastically determined mortality rates, depending on whether the winter is harsh and/or the summer has a disease epidemic. The model results suggest that given the poor data available, a relatively safe strategy for managers, producing reasonable yields, would be to hunt at a low hunting mortality rate, taking up to 6% of the population each year, while selecting strongly for males. 4.  A simpler lumped‐parameter model is developed using the climate and disease‐determined rates of population increase derived from the age‐ and sex‐structured model. Comparison between the two models shows that the lumped parameter model is an adequate simplification of the age‐ and sex‐structured model, although it underestimates equilibrium population sizes somewhat. 5.  The simplified model is used to investigate the available data on the Mongolian gazelle. It is shown that the population must have been larger than previous estimates in order to have sustained the level of recorded hunting over the last 64 years. 6.  The model suggests that the population declined rapidly from 1979 to 1986, then stabilized. Variation in natural mortality rates has had an effect on the rate of decline since 1932, but recorded hunting has not. It is not possible to tell whether the rates of unrecorded hunting or habitat degradation have changed since 1932. The results are robust to parameter variation.
Traditional farming and key foraging habitats for chough Pyrrhocorax pyrrhocorax conservation in a Spanish pseudosteppe landscape
Authors: Blanco Guillermo , Tella JosÉ L. , Torre Ignacio 
Published: March 2003

1.  Agricultural land devoted to low‐intensity practices supports many declining bird species in Europe. The potential effects of intensification or abandonment of traditional farming practices are assessed from the point of view of the conservation of the chough Pyrrhocorax pyrrhocorax. 2.  The study was conducted in Los Monegros (north‐east Spain), in a pseudosteppe landscape of special relevance for this species. In this area traditional farming survives in the form of low‐intensity arable systems including fallowing and extensive sheep grazing. 3.  Foraging choughs showed a strong selection for field margins, avoided any remnant of the original scrubland and halophitic vegetation, and utilized other habitats maintained by traditional crop rotation (e. g. fallow, stubble) at different times of the year. 4.  A highly complex pattern of habitat selection was found which was not only related to seasonal changes in habitat availability, but also differed between territorial pairs and the non‐breeding population. This emphasizes the importance of taking all the different components of bird populations into account when analysing interactions between habitat selection and the annual farming cycle. 5.  Chough habitat selection suggests that both agricultural intensification and land abandonment would have detrimental consequences for this species in Los Monegros. The maintenance of traditional farming is recommended, especially by promoting the use of long fallow rotations grazed extensively by livestock, encouraging the increase of grassland edges around landholdings and sand roads, and maintaining a low input of biocides. These management measurements could also favour most other endangered species of steppe birds, and could be supported by the establishment of Zonal Programmes under the CAP Agri‐Environment Regulation (2078/92).
Using species abundance models as indicators of habitat disturbance in tropical forests
Authors: Hill Jane K. , Hamer Keith C. 
Published: March 2003

1. In temperate communities, species abundance distributions have been used to detect ecosystem disturbance: in undisturbed habitats, distributions are claimed to generally fit log‐normal models, whereas in disturbed habitats, distributions fit log‐series models. 2. There is a growing literature on the effects of habitat disturbance in tropical ecosystems and several studies suggest that species abundance models may be useful in detecting disturbance, although data are lacking. 3.
Nummelin (1998) claims that these models are not universal indicators of forest disturbance, but we highlight a number of problems with the data presented in Nummelin's study and conclude that it is too soon to dismiss these models. We discuss several important points arising from Nummelin's study which need to be considered if species abundance models are to be used appropriately.
Identifying trends in land degradation in non‐equilibrium rangelands
Authors: Pickup G. , Bastin G. N. , Chewings V. H. 
Published: March 2003

1. Change in environmental conditions in the complex non‐equilibrium rangelands of arid Australia is difficult to monitor. We show how trends in rangeland condition can be identified from changes over time in the pattern of vegetation growth across gradients of differing grazing intensity. 2. Grazing intensity was measured indirectly using distance from water. Vegetation growth was derived from remotely sensed vegetation index values before and after large rainfalls. The amount of growth was adjusted for initial vegetation cover to give a standard measure of vegetation response. 3. A vegetation response ratio was derived by comparing areas less than 4 km from water with benchmark areas further away. Systematic changes in this ratio over time indicate a trend. 4. Ratio values from test areas suggested decline, improvement and no change, consistent with recent management history. 5. The method can be applied where the whole area is affected by grazing and relatively pristine benchmarks are unavailable. It could therefore be useful in the semi‐arid rangelands where paddocks are smaller than in the arid part of Australia. It also has possible uses in the rangelands of Africa and the Americas. There is potential for applying the method to traditional grazing systems as well as to commercial pastoralism. 6. The method is cheaper and more effective than other techniques and increases the capacity of grazing gradient‐based monitoring schemes for arid and semi‐arid areas.
Macroinvertebrate distributions and the conservation value of aquatic Coleoptera, Mollusca and Odonata in the ditches of traditionally managed and grazing fen at Wicken Fen, UK
Authors: Painter Duncan 
Published: March 2003

1. Water‐filled ditches are an important ecological feature of lowland Britain. Originally dug to facilitate wetland drainage, ditches often provide refuges for aquatic flora and fauna of high conservation value. 2. The ditches, ponds and major waterways of a traditionally managed undrained fen and the ditches of a previously drained cattle‐grazed fen meadow were sampled at Wicken Fen National Nature Reserve for Coleoptera, Mollusca and Odonata, and for physical, chemical and biological variables. 3. Multivariate analysis showed a clear division between ditches on the two fens, and between larger and smaller waterbodies. 4. Individual ditches possessed distinctive faunas. Ditch age and bank profile were important factors influencing faunal species composition. 5. Invertebrate distributions were shown to be significantly correlated with macrophyte distribution. 6. Waterbodies were ranked in terms of their species quality, using a point‐scoring system; there was no correlation between rankings for the three invertebrate groups; only ditch age and detritus levels were correlated with species quality score (for Coleoptera). 7. Ditch management recommendations are discussed in the light of these results.
Breeding success and causes of breeding failure of curlew Numenius arquata in Northern Ireland
Authors: Grant Murray C. , Orsman Chris , Easton Jon. , Lodge Chris , Smith Malcolm , Thompson Guy , Rodwell Stephen , Moore Niall 
Published: March 2003

1. The present study investigated breeding success and causes of breeding failure of curlew, a species for which the UK holds internationally important breeding numbers. Studies were undertaken between 1993 and 1995 in two areas of Northern Ireland, where the species’ breeding range has recently contracted and breeding numbers are declining. Avian nest predators were abundant in both areas, whereas foxes were abundant on the Antrim study area but generally were absent from the Lough Erne study area, which was mainly islands. 2. Productivity was estimated to be 0·14–0·26 fledglings per pair in Antrim and 0·20–0·47 fledglings per pair on Lough Erne. These figures are lower than most estimates of productivity from other studies of breeding curlew. The differences between the recorded productivity levels and those estimated to be required to maintain a stable population are sufficient to account for the observed decline in Northern Ireland's breeding curlew population. 3. Predation was the main proximate cause of breeding failure, with nest predation being of most importance in reducing productivity. Only 3·6–19·0% of all nests hatched on each study area in each year, with nest predation accounting for 85–97% of failures. Survival of chicks from hatching to 31 days of age was 38·5% in Antrim and 19·1–29·2% on Lough Erne. Predation accounted for 74% of chick mortality. 4. Nest failure rates were not related to the vegetation height around nests nor to clutch laying date on either study area. They differed among the islands and one shoreside site on Lough Erne. Almost all nest predation on Lough Erne was attributable to avian predators, but in Antrim foxes probably accounted for most nest predation. The likelihood of predation on chicks was not related to their hatching date, hatching weight or body condition. 5. The results from this study suggest that predation rates on curlew nests in Northern Ireland may have increased in recent decades. Levels of predator control in Northern Ireland have declined but there have also been considerable changes in land‐use that could benefit generalist predator species or increase the vulnerability of curlew nests to predation. It is recommended that large‐scale trials of legalized predator control and land‐use manipulation should be undertaken to identify appropriate conservation management methods.
Restoration of ecosystem function in an abandoned sandpit: plant and soil responses to paper de‐inking sludge
Authors: Fierro Alejandro , Angers Denis A. , Beauchamp Chantal J. 
Published: March 2003

1. In minesoil reclamation, the establishment of a sustainable plant cover requires the improvement of limiting conditions and the re‐initiation of carbon (C) and nutrient cycling. 2. The approach used in this study for reclaiming an abandoned sandpit in Quebec, Canada, was based on a heavy organic amendment as an attempt to accelerate the reconstruction of a functional ecosystem. 3. The one‐time intervention consisted of incorporating paper de‐inking sludge into soil at two rates (0 and 105 dry t ha–1), supplemented with nitrogen (N) at three rates (3, 6 and 9 g kg–1 sludge) and phosphorus (P) at two rates (0·5 and 1·0 g kg–1 sludge) followed by seeding (mid‐summer) of Agropyron elongatum (Host) Beauv. (tall wheatgrass). 4. Standing biomass increased in the presence of sludge after both the first and second full growing seasons. High N application rates further increased yield, more importantly in the second season. The high P rate improved grass establishment in all cases. Ground cover increased with time and doubled in the presence of sludge whereas it declined in the absence of sludge. Phosphorus and N uptake was improved consistently in the presence of sludge. 5. Sludge application resulted in improved water retention and cation exchange capacities, and an increase in pH and bulk density of sandpit minesoil, all of which may have accounted for the significant improvement in plant responses. Levels of soil C and N suggest that this reconstructed system is approaching sustainability. 6. Adequate N and P supplements will accentuate the positive influence of sludge on revegetation.
The persistence of a SIS disease in a metapopulation
Authors: Foley Janet E. , Foley Patrick , Pedersen Niels C. 
Published: March 2003

Summary1. Deterministic models predict that susceptible‐infective‐susceptible (SIS) disease, where there is no immunity to reinfection following recovery, will become infinitely persistent in a host population. We explored the incorporation of stochasticity into SIS models; modelled interacting host‐disease agents in metapopulations; and examined model predictions in a real system involving viral infection in domestic cats.2. SIS models incorporating stochasticity predicted that disease persistence would be finite and dependent on the host population size, provided the host population was isolated. However, the disease may persist by dynamic spread among interacting host metapopulations.3. Feline enteric coronavirus (FECV) dynamics in domestic cats were well predicted by stochastic metapopulation models.4. The models we present are mathematically tractable, generalizable, and mechanistically realistic. The findings from the cat‐virus system are immediately applicable to the management of cattery populations and could be adapted to inform eradication programmes for other infectious diseases in animal and human populations. The most practical methods to eradicate feline enteric coranovirus would be to remove small catteries (islands) from interactions with large catteries (mainlands) and to convert mainlands to islands by depopulation.
Age structure and density of red‐capped robin populations vary with habitat size and shape
Authors: Major Richard E. , Christie Fiona J. , Gowing Greg , Ivison Tessa J. 
Published: March 2003

Summary 1. In order to determine the influence of habitat shape on aspects of the population dynamics of birds, 196 male red‐capped robins Petroica goodenovii were surveyed using song playback in large non‐linear woodland remnants and linear roadside remnants in the wheatbelt of south‐eastern Australia. 2. The average density of male robins was significantly higher in large non‐linear remnants [0·86 ± 0·09 (SD) birds ha–1] than in small linear remnants [0·35 ± 0·16 (SD) birds ha–1]. 3. Red‐capped robins exhibit delayed plumage maturation, and 14% of the males captured were yearlings. This percentage was significantly higher in roadside remnants (20%) than in large, non‐linear remnants (8%). 4. These results indicate that different population processes are occurring in the individual remnants and the dynamics of the metapopulation are potentially complex. 5. Land managers must not focus excessively on wildlife corridors (narrow, linear habitats) at the expense of appropriate management and restoration of large areas of native vegetation.
Can population surveys show if the Mediterranean monk seal colony at Cap Blanc is declining in abundance?
Authors: Forcada Jaume 
Published: March 2003

Summary 1. The Mediterranean monk seal is an endangered marine mammal with only a few populations thought to be viable. The largest aggregation of this species is found at the Peninsula of Cap Blanc, on the western Sahara, where a colonial structure is maintained. The size of this colony is estimated by annual capture–recapture surveys, but it is unclear if the attained level of precision is enough to detect changes in numbers in the short term. 2. In this study, simulated capture–recapture experiments were used to investigate the relationship between population estimates and abundance. The statistical power necessary to detect a population decline with ongoing surveys was estimated, and the requirements for an improvement in precision were evaluated. Additionally, changes in abundance over consecutive surveys were examined for comparison with an alternative method of Bayesian inference. 3. Results indicated that the power to detect trends from the actual surveys was lower than should be required for the conservation of a small population, such as the colony at Cap Blanc. A 5% annual rate of decline in abundance would only be detected with high power after 12 years, with a population of 317 seals being reduced to 172. If the annual rate of decline was 10%, 8 years would be required to detect a reduction of 317 to 136 seals. 4. Capture–recapture surveys can produce reliable data but do not identify moderate or low population declines. The increase in precision of surveys is costly and time consuming, and other monitoring methods are needed to detect early signs of a decline. Bayesian methods cannot provide a better result because they are not robust to small sample size and heterogeneity in capture probabilities. Despite the need for alternative methods for earlier detection, capture–recapture surveys are still required to estimate the size of the colony, and precision in population estimates can be evaluated in relation to cost effectiveness.
Impact of the Onopordum capitulum weevil Larinus latus on seed production by its host‐plant
Authors: Briese D.T. 
Published: March 2003

Summary 1.
The impact of the oligophagous capitulum weevil Larinus latus on seed production by its host Onopordum species was studied in its native range in order to assess its potential as a biological control agent of these thistles in Australia. 2.
Field surveys in Greece during 1988–89 showed a strong positive relationship between attack levels of L. latus and seed destruction in Onopordum species Differences in attack levels were found between populations of different species, with heavier attack on those having larger capitula. 3.
In the case of O. bracteatum, attack levels attained 100% with total seed destruction. More detailed studies at one location over a full season in 1991 confirmed that L. latus is the dominant capitulum insect, being responsible for the loss of 37% of seed, compared with 8% for the lepidopteran Homeosoma nebulella and 2% for the tephritid fly Tephritis postica. 4.
A regression surface was produced that estimated seed loss in terms of capitulum size and number of developing L. latus larvae. This provides a tool for measuring overall population seed loss from easily measurable parameters. 5.
While able to reduce seed production by Onopordum thistles severely in a single season, the longer‐term impact of these weevils on their host‐plant population dynamics may not be as great. Onopordum species have long‐lived seed banks and thus escape in time will dampen the effects of high seed loss in any one year. Moreover, populations of L. latus are themselves subject to density‐dependent regulatory processes that would further buffer the system. 6.
This weevil was released in Australia in 1992 for the control of Onopordum thistles, and these findings suggest that L. latus would be most effective as part of a complementary guild of biological control agents.
Quantifying changes in abundance of food plants for butterfly larvae and farmland birds
Authors: Smart S. M. , Firbank L. G. , Bunce R. G. H. , Watkins J. W. 
Published: March 2003

Summary 1. Recent changes in population size of butterflies and farmland birds across north‐west European landscapes have been linked to the effects of agricultural intensification. Reduction in food supply has been postulated as one of the proximal causes of these trends but the generality of this explanation has not been tested at a large scale and across animal species. 2. Changes in abundance of food plants for butterfly larvae and lowland farmland birds in the British countryside were analysed for the period 1978–90 using data from fixed plots recorded as part of the countryside surveys of Britain. 3. Associations were sought between these changes and trends in population size of selected butterflies and birds recorded from long‐term monitoring schemes. 4. No associations were found between change in abundance of food plants and either increasing, stable or decreasing animal groups. At the level of individual animal species, significantly more decreases than increases in food plant frequency were found for herbivorous bird species irrespective of population trend. The size of the reduction in food plant frequency was also significantly greater for the declining bird group than for stable or increasing groups. 5. Few significant associations were detected between population trend and food plant trend for butterfly species. However, the results suggested a positive relationship between increasing butterflies and increased abundance of Elytrigia repens and Urtica dioica. 6. Food plants that increased in abundance comprised species favoured by lack of management and increased nutrient availability. Increases in abundance were also associated with linear landscape features such as hedges and streamsides. Decreasing plant species included arable weeds and stress‐tolerant species typical of unimproved grasslands. 7. Based on evidence of local associations between animal and food plant change and the need for viable populations of food plants to exist within the range of each animal species, we support measures designed to enhance and maintain populations of declining food plants. Much evidence now exists to identify practical measures that husband food resources for many bird and butterfly species. The challenge for conservation policy is to manage their implementation at scales necessary to influence national trends.
Time budgets and foraging of breeding golden plover Pluvialis apricaria
Authors: Whittingham M.J. , Percival S.M. , Brown A.F. 
Published: March 2003

Summary 1. The golden plover Pluvialis apricaria is of high conservation concern in Europe. Previous studies have concentrated on how birds utilize moorland. We used radio‐telemetry to study their habitat selection and behaviour, during both night and day, in an upland landscape of enclosed fields and moorland in county Durham, UK. 2. During incubation adult golden plover fed principally in enclosed fields 1·1–3·7 km from their moorland nests, but spent less than 5% of their foraging time on moorland. In contrast, birds with broods spent around 85% of their time foraging on moorland. 3. Birds on moorland selected calcareous grassland and avoided old stands of dense tall heather (> c. 12 cm). Younger, shorter (< c. 5–8 cm), sparser heather was used as much as would be expected by chance. Mires of harestail cotton grass Eriophorum vaginatum, the dominant community type when heather Calluna vulgaris is heavily grazed, was selected on both moorland sites. 4. Only 17 of 85 fields in the study area were used for foraging by breeding golden plover. The number of molehills, a reported indicator of earthworm abundance, was the best single variable explaining field choice. Both field size and distance from road had small but significant effects on field choice. 5. We advocate that groups of enclosed fields regularly used by golden plover during the breeding season be afforded specific protection under conservation schemes (e.g. environmentally sensitive area agreements). Conservationists wishing to locate such fields should look for areas with high earthworm populations, as indicated by molehills, close (< 4 km) to breeding populations of golden plover. Rank heather on flat or gently sloping ground should be kept short by appropriate burning or grazing. Areas of calcareous grassland should be preserved. 6. These data illustrate the value of detailed radio‐telemetry in informing equally detailed habitat management for important bird species.