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1.
Capsule Improving habitat quality through late or intermittent mowing may increase passerine population density without reducing reproductive success.

Aim To describe the relationship between passerine territory density (TD) and Whinchat Saxicola rubetra and Yellow Wagtail Motacilla flava hatching success, under different management regimes.

Methods TD was defined by the Territory Mapping method in nine sites selected in five French flood plains, in four intermittently mown meadows in Russia and in four additional French sites where mowing was partially postponed. Hatching success was assessed by the observation of prey carrying. Generalized Linear Mixed Models were used to analyse the influence on hatching rates of mowing management, early mowing and TD. Linear Mixed Models were used to study the effect of mowing management on TD.

Results In French early mown meadows, TD affected reproductive success. Higher hatching rates and TD were observed in Russia. Similar results in French study sites with postponed mowing confirmed the influence of mowing management on carrying capacity.

Conclusion In west-European grassland systems, late or intermittently mown patches within or at the edge of meadow areas, with potentially improved invertebrate-prey availability, should help to sustain bird demography and improve the efficiency of current conservation programmes.  相似文献   

2.
Capsule Breeding wader populations have more often shown declines than passerine populations during the last 10–20 years.

Aims To determine abundance changes in British upland breeding birds during the last 10–20 years.

Methods We re-surveyed 1348 km2, in nine study areas, of the British uplands in 2000 and 2002, which had been previously surveyed between 1980 and 1991. In addition, we included data from recent repeat surveys in four other upland areas, covering approximately 365 km2, to broaden the scope of our study.

Results We found evidence of widespread population declines in three species of breeding waders, Lapwing Vanellus vanellus, Dunlin Calidris alpina and Curlew Numenius arquata. Among the passerines, some species declined, including Twite Carduelis flavirostris and Ring Ouzel Turdus torquatus, while others showed strong gains, including Stonechat Saxicola torquata and Raven Corvus corax.

Conclusion Overall, abundance changes were characterized by a high degree of variability across study areas, even when close together. This variability may have been partly due to the different time intervals between the original and repeat surveys. Improved upland breeding bird population monitoring is needed to allow better detection of trends. Action is needed to restore upland breeding bird populations in areas where they have declined.  相似文献   

3.
Capsule Woodland birds were significantly less likely to occur in gardens in years of high beechmast crop.

Aim To test the hypothesis that woodland species that feed on beechmast will have significantly lower occurrence rates at garden feeders in mast years.

Methods Weekly winter occurrence rates at garden feeders between 1970/71 and 1999/2000 for 40 species were analysed in relation to annual beechmast abundance, classified into low, medium and high years. A repeated-measures logistic regression model was used to assess whether beechmast abundance explained further significant variation additional to underlying seasonal and annual trends.

Results Seven species that commonly feed on beechmast showed significantly lower occurrence in gardens in years of highest beechmast abundance: Great Spotted Woodpecker Dendrocopos major, Woodpigeon Columba palumbus, Great Tit Parus major, Coal Tit Periparus ater, Nuthatch Sitta europaea, Jay Garrulus glandarius and Chaffinch Fringilla coelebs. Blackbird Turdus merula and Siskin Carduelis spinus, which showed similar significant patterns, are likely to take beechmast as elements of their diet. Pied Wagtail Motacilla alba was the only insectivorous species to show significant effects, but occurrence was lowest in years of intermediate beechmast abundance. For the latter species, this may have been due to confounding effects of temperature, but there were no such confounding effects of either temperature, or the number of bird feeders provided in gardens, for the other nine species.

Conclusion Use of artificial food sources by birds in gardens is influenced by resources in the surrounding countryside, suggesting that food provided in gardens may play a significant part in the population dynamics of these species, that population monitoring without consideration of the garden habitat may be deficient, and that volunteer-based garden bird recording may provide data that can be used as an indicator of changes in the wider countryside.  相似文献   

4.
Ecological interactions between native species are often disturbed by invasive species. However, to understand their impact on wild native animal populations on a country scale it is necessary to develop a predictive model. Therefore, I followed the species density distribution modelling approach to explore how feral domestic cats (Felis catus) along with environmental predictors determined densities of two bird species, the Yellowhammer (Emberiza citrinella) and the Yellow Wagtail (Motacilla flava) on the whole area of Poland. As a modelling method, I used the Generalised Additive Model to develop two models for each of the two bird species: The first with the feral cat density as an additional predictor, and the second without it. As a result, I demonstrated the negative impact of cat density on native bird populations, illustrated by reduced density of the two studied species in their preferred habitats, in which cats reached a high density. Although it cannot be explicitly asserted that cats lead to a local extinction of the two bird species, these predators should not be underestimated. In many locations feral populations are fed with new individuals, and they do not follow the same internal mechanisms regulating their population as the native bird fauna. Thus, on a large spatial scale species density distribution models of birds should include cats’ population size as an additional predictor when this predator's environmental preferences overlap with preferences of the studied target groups.  相似文献   

5.
Close to the edge: predation risks for two declining farmland passerines   总被引:1,自引:1,他引:0  
Data on the breeding success of two crop-nesting passerines, Skylark Alauda arvensis and Yellow Wagtail Motacilla flava , were collected in relation to linear features within and surrounding arable crops. Both species were found to experience high rates of nest predation with increased proximity to field boundaries, although the exact nature of the relationship differed with species and, in the case of Skylark, with boundary type. Most nest losses were attributable to predation. During 2006 video cameras deployed on Skylark nests showed that all recorded predation was by mammals of various species, and that these were most active in or around grass margins. The results suggest that further research is needed into ways of minimizing negative impacts of predation on Skylarks. Possible solutions discussed include concentrating Skylark Plots in the field centres away from grass margins and promoting Skylark Plots in fields without grass margins in future agri-environmental schemes.  相似文献   

6.
CapsuleWe present evidence of large declines in numbers of breeding waders and passerines in some upland areas since the 1970s.

Aims Changes in numbers of ground-nesting birds are documented for two areas of the Pennines and are qualitatively related to recent land-use history.

Methods Territory mapping was used to estimate bird numbers on two areas (76 and 99 ha) in the Pennines for which more than 10 consecutive years of data were available from the BTO's Common Birds Census archives.

Results At both sites there were large declines in Lapwing Vanellus vanellus, Snipe Gallinago gallinago, Skylark Alauda arvensis, Twite Carduelis flavirostris and Reed Bunting Emberiza schoeniclus. The two sites differed in the timing of the declines but for Twite the trends were almost identical. By the late 1990s, numbers of most ground-nesting birds were far lower than in the 1970s. There was relatively little change in numbers of species breeding at either site.

Conclusions Progressive changes in land-use, involving loss of rough grassland and a switch from dairy to sheep farming, may have contributed to the declines at one of the sites. However, there was no obvious change in land-use or habitat loss at the other site where population declines began 5 to 10 years earlier. Such declines have probably occurred widely in moorland-edge areas during the last 30 years and multiple factors may be responsible.  相似文献   

7.
ABSTRACT.   The nesting biology of the Eastern Yellow Wagtail ( Motacilla tschutschensis ) was studied at Cape Romanzof, Alaska, an arctic tundra site on the Bering Sea coast near the northeastern limit of the breeding distribution of the Yellow Wagtail ( Motacilla flava/citreola/tschutschensis ) species complex. Ninety-four nests were located and monitored from 1996 to 1999. Females built nests in 5–7 d, and nests were located on the ground. The mean clutch size was 5.6 eggs, and the mean incubation period was 11 d. Both adults incubated, and some males had a partial brood patch. The mean duration of the nestling period was 11.6 d, and both parents brooded and fed the young. Some adults began the complete prebasic molt (including primaries) while their young were still in the nest. Nestling development was similar to that reported for other Yellow Wagtails ( sensu lato ), but the breeding cycle and breeding season of Eastern Yellow Wagtails was compressed relative to Western Yellow Wagtails in Europe and to other passerine species breeding in western Alaska. Some breeding events overlapped, including initiation of egg laying before completion of nest building and initiation of adult molt while young were still in the nest. Clutch sizes were larger than reported for most European relatives. Clutch size generally fit with models predicting an increase of about one egg per 19 degrees of increased latitude. Rapid nest initiation, overlap of breeding cycle events, nest attendance (including incubation) by males, and slightly larger clutches appear to be adaptations to high-latitude breeding in this long-distance migrant.  相似文献   

8.
Patterns of change in distribution (presence/absence) and abundance since the late 1960s were examined in 20 species of farmland bird in southern Britain in predominantly arable (eastern), predominantly mixed (central) and predominantly grassland (western) regions. Comparisons were made between changes in distribution and in abundance to determine whether these measures show similar relationships to environmental change. Local extinctions of selected species and reductions in species richness were significantly greater in the predominantly grassland region. Decreases in abundance were greatest in seven species in the predominantly arable region, two in the mixed region and nine in the grassland region. Changes in distribution and abundance showed consistent patterns in three species, turtle dove Streptopelia turtur L., yellow wagtail Motacilla flava L. and reed bunting Emberiza schoeniclus L. In another four species, grey partridge Perdix perdix L., lapwing Vanellus vanellus L., tree sparrow Passer montanus L. and corn bunting Miliaria calandra L., decreases in abundance were greatest in the arable region, yet declines in distribution were lowest. For other individual species, changes in distribution were too small to draw any conclusions in relation to farm type. We suggest that modern grassland systems are suboptimal habitats compared to arable or mixed agricultural land for many farmland species that occur at relatively low density in the more western, grass‐dominated region. Declines in abundance are therefore more likely to lead to local extinction in these areas than in eastern areas where abundance is higher. However, the role of changes in grassland management on bird populations requires further research. It is suggested that conclusions drawn from changes in distribution alone, in the absence of supporting data on changes in abundance, may be misleading where the aim is to assess how large‐scale spatial dynamics of populations relate to environmental change.  相似文献   

9.
Modern, intensive grassland management has led to strong declines in ground‐nesting grassland birds, and is now increasingly threatening the last remaining strongholds of the Whinchat Saxicola rubetra in the Central European uplands. In this study, we assess key threats to Whinchat populations in these uplands in order to suggest appropriate conservation measures. We compared the direct threat of early mowing as well as the indirect threat resulting from a deteriorating arthropod food source in an inner‐alpine valley. Five of our seven study sites were mown too early with respect to the chicks' fledging date. Such early mowing was particularly evident on the more intensively farmed, earlier mown valley bottoms than on the valley slopes. Arthropod abundance and biomass did not differ between valley bottoms and slopes. However, valley bottoms had a greater amount of unprofitable prey items such as flies. Breeding bird density was mainly determined by the degree of overlap between the mowing schedule and breeding phenology. These findings suggest that in upland grasslands at an early stage of intensification, early mowing is of greater importance for populations than possible negative effects of a reduced food source. We suggest that mowing is delayed until a sufficient proportion of nestlings are safely fledged.  相似文献   

10.
The apparent adult survival rate is one of the key population parameters of migratory birds. The widely used Cormack–Jolly–Seber capture–mark–recapture model has a number of disadvantages, the main one of which is the impossibility of discerning mortality and permanent emigration. The accuracy of survival estimates can be increased using a multistate capture–mark–recapture model, with the help of which it is possible to assess the survival of successful and unsuccessful birds separately. We used this model to estimate the apparent survival rates of adults in local populations of three ground-nesting passerines: Booted Warbler (Iduna caligata), Whinchat (Saxicola rubetra), and Yellow Wagtail (Motacilla flava), all breeding on abandoned agricultural lands. We studied the reproductive success of 472 marked pairs and analyzed individual capture histories of 814 birds. The previous reproductive success was found to influence significantly the apparent survival of adults. This relation was best expressed in the Yellow Wagtail (apparent survival of successful birds, φ = 0.39 ± 0.06, vs. that of unsuccessful birds, φ = 0.19 ± 0.06) and the Whinchat (apparent survival of successful birds, φ = 0.32 ± 0.05, vs. apparent survival of unsuccessful birds, φ = 0.10 ± 0.05), but a little lower in the Booted Warbler (apparent survival of successful birds, φ = 0.33 ± 0.17, vs. apparent survival of unsuccessful birds, φ = 0.16 ± 0.13). Unsuccessful individuals leave the study area for good, while most of the successful birds return there the next year. Thus, the apparent survival rate of passerines evaluated with capture–recapture models is determined to a considerable degree by the previous reproductive success within local populations.  相似文献   

11.
Capsule: The direction and magnitude of changes in structure of UK woodlands since the 1980s, are inconsistent with them playing a causative role in the declines of four migrant bird species in upland oak woods.

Aims: To investigate whether changes in woodland structure were a possible cause of population changes of four Afro-Palearctic migrants (Wood Warbler Phylloscopus sibilatrix, Tree Pipit Anthus trivialis, Pied Flycatcher Ficedula hypoleuca and Common Redstart Phoenicurus phoenicurus) in the upland oakwoods of western and northern Britain.

Methods: Bird population estimates and measures of woodland structure were recorded in two time periods 1982–85 and 2003–04 across six regions of the UK. We modelled the effect of habitat change and initial habitat state on population changes between the two time periods. The predicted effects of habitat change on populations were then compared with observed population changes across the different regions.

Results: All four species underwent population declines; there were also significant increases in ground cover and understorey cover. The number of birds in 2003–04 was influenced by habitat structure at this time in addition to showing regional differences. Change in bird numbers varied between regions and was affected by both the initial habitat state and change in habitat structure, with regional variation in the effect of habitat change. There was however no relationship between the predicted effect of change in habitat structure on population size and observed regional population changes.

Conclusions: Changes in woodland structure are unlikely to be the main driver of population change in these four migrant bird species, and large-scale factors affecting demographics in other parts of their breeding range or in their wintering areas are likely reasons for local population declines.  相似文献   


12.
Capsule: Changes in abundance of six bird species showed associations with moorland management.

Aims: To assess responses of breeding birds to moorland management over a 14-year period.

Methods: Vegetation and birds were surveyed at 2–3-year intervals and changes examined in relation to sheep and cattle grazing, vegetation burning and cutting.

Results: Seven correlations between change in management and change in bird abundance were detected, and six between change in vegetation and change in bird abundance. On plots where sheep numbers declined, Golden Plover Pluvialis apricaria and Northern Wheatear Oenanthe oenanthe declined. Where a greater area was burned, Golden Plover increased in the initial post-burning period but Red Grouse Lagopus lagopus scotica declined. Eurasian Curlew Numenius arquata and Sky Lark Alauda arvensis increased where a greater area of moorland vegetation was cut. Whinchat Saxicola rubetra declined with increasing cattle numbers on a plot.

Conclusions: Bird populations respond to changes in moorland management, but these changes are not always associated with detectable changes in vegetation. These responses of moorland breeding birds to management could help refine agri-environment options and other conservation interventions on moorland. Responses differed between bird species, ideally requiring site-specific planning where managing for multiple species is a goal.  相似文献   


13.
In common with many other previously widespread British birds, Yellow Wagtail Motacilla flava flavissima populations have declined substantially in the UK in recent decades. Recent national data suggest particular problems in grassland. We investigated how habitat management in a grassland area of East Anglia, England, influenced the habitat selection of this species. Breeding territories were associated with fields previously subject to prolonged winter floods and which contained shallow-edged ponds or wet ditches during summer. Territories were also associated with fields with short, sparse swards and high proportions of bare earth within the sward, and these features were themselves associated with previous winter flooding. However, nests were associated with taller swards than were random points within the same field, suggesting that Yellow Wagtails would benefit from within-field heterogeneity of sward height to provide both nesting and foraging habitat. We discuss how grazing, cutting and water-level management regimes could be used to promote optimal sward structure for Yellow Wagtails.  相似文献   

14.
This study showed from the analysis of 180 droppings of the Grey Wagtail Motacilla cinerea harvested during a period of one year from the Babors Mountains (Bejaia, Algeria) that insects formed the main part of the diet (85.9% of identified items). The other food categories included arachnids, crustaceans and gastropods. Among the insects, Coleoptera (beetles) was the main order consisting of 37.4% of identified items. The most frequently recorded family was Baetidae (Ephemeroptera; 9.8%). At the prey-taxa level, an unidentified Baetidae was the most frequently encountered and represented 9.7% of the diet. This species was present in the diet throughout the year. Prey taxa classified as aquatic were more frequently encountered (54.2%) compared with those considered terrestrial. This study showed that seasonal fluctuations in the diet of Grey Wagtail were very weak. Prey size ranged from 0.2 to 30.5 mm, with an average of 8.9 mm. Overall, this study showed that Grey wagtail fed on species of a wide variety of taxa, with little variation across the year.  相似文献   

15.
Capsule Winter Atlas surveys of 16 species on lowland farmland revealed significant changes in count for four species.

Aims To estimate changes in abundance between the early 1980s and late 1990s, of wintering seed‐eating passerines, in ‘core’ areas of lowland Scotland.

Methods Ninety‐five Scottish 10‐km squares were selected that held high numbers of seed‐eating passerines in the 1981–84 Atlas of Wintering Birds in Britain and Ireland. The same survey methods were used to resurvey these in winters 1997/98 and 1998/99, and visits were matched as closely as possible for duration and date. Analyses compared counts between the two survey periods for 16 species of seed‐eating passerines and, for 12 of these, differences were also compared with national breeding population trend information for the same period.

Results Mean Corn Bunting Emberiza calandra count per visit declined by 62% between the early 1980s and late 1990s, a difference which was statistically significant (P = 0.026). Significant increases were recorded for Yellowhammer Emberiza citrinella (up 62%), Common Linnet Carduelis cannabina (up 3.4‐fold) and European Goldfinch Carduelis carduelis (up 13‐fold). For 12 species for which national breeding population trend data were available, trends were weakly positively correlated (r s = 0.43, P = 0.08) with those from our results, but several species trends were more positive in our study. This difference was particularly marked for Eurasian Tree Sparrow Passer montanus, Goldfinch and Linnet.

Conclusion Repeating Winter Atlas surveys offers a useful additional method for assessing population trends. They are particularly useful in a region with low observer coverage and for species that are poorly covered by long‐term bird monitoring data sets. It would be valuable to validate this approach at a regional level, especially in a region for which detailed long‐term bird monitoring data are available.  相似文献   

16.
Capsule Large buntings prefer cereal grains whilst sparrows also take oily seeds.

Aims To determine seed food preferences of Tree Sparrow Passer montanus and Corn Bunting Emberiza calandra.

Methods Forty seed choice experiments were conducted at two sites over two winters. In each experiment, two seed types were provided and the number of visits made by birds to each type was recorded over a set period. At one site, Tree Sparrows were colour-ringed, allowing choices made by individual birds to be recorded. Data were also collected for House Sparrow Passer domesticus, Yellowhammer Emberiza citrinella and Reed Bunting E. schoeniclus.

Results All five species fed intensively on cereal grain, and wheat and oats were consistently preferred to barley. Sparrows and Reed Buntings also took maize, which was avoided by Corn Bunting and Yellowhammer. Tree Sparrow exhibited a broad diet, selecting cereal grain and oily seeds including sunflower and oilseed rape, but rye-grass seed was almost completely avoided.

Conclusion Cereal grain should be a key component of over-winter provision of seed for farmland passerines, especially when targeted at Corn Bunting and Yellowhammer. Oily seeds such as brassicas and sunflower will benefit species with more generalist diets, including Tree Sparrows.  相似文献   

17.
There has been a rapid decline of grassland bird species in the UK over the last four decades. In order to stem declines in biodiversity such as this, mitigation in the form of newly created habitat and restoration of degraded habitats is advocated in the UK biodiversity action plan. One potential restored habitat that could support a number of bird species is re-created grassland on restored landfill sites. However, this potential largely remains unexplored. In this study, birds were counted using point sampling on nine restored landfill sites in the East Midlands region of the UK during 2007 and 2008. The effects of restoration were investigated by examining bird species composition, richness, and abundance in relation to habitat and landscape structure on the landfill sites in comparison to paired reference sites of existing wildlife value. Twelve bird species were found in total and species richness and abundance on restored landfill sites was found to be higher than that of reference sites. Restored landfill sites support both common grassland bird species and also UK Red List bird species such as skylark Alauda arvensis, grey partridge Perdix perdix, lapwing Vanellus vanellus, tree sparrow, Passer montanus, and starling Sturnus vulgaris. Size of the site, percentage of bare soil and amount of adjacent hedgerow were found to be the most influential habitat quality factors for the distribution of most bird species. Presence of open habitat and crop land in the surrounding landscape were also found to have an effect on bird species composition. Management of restored landfill sites should be targeted towards UK Red List bird species since such sites could potentially play a significant role in biodiversity action planning.  相似文献   

18.
Conservation concern about granivorous birds has led to the implication of changing agricultural practices as causes of widespread population decline. We investigate relationships between breeding performance and the agricultural environment for ten granivorous farmland bird species (Stock Dove Columba oenas, Skylark Alauda arvensis, Tree Sparrow Passer montanus, Chaffinch Fringilla coelebs, Greenfinch Carduelis chloris, Linnet C. cannabina, Bullfinch Pyrrhula pyrrhula, Reed Bunting Emberiza schoeniclus, Yellowhammer E. citrinella and Corn Bunting Miliaria calandra). We analyse long-term, extensive data from the British Trust for Ornithology's Nest Record Scheme on breeding performance per breeding attempt with respect to farmland type (arable, grazing or mixed) and time (pre- and post-1975–76). The influence of habitat is investigated at two different scales: within the nesting territory and at the landscape level. Relationships between farmland type and (temporal changes in) breeding performance tended to be species-specific, but a few patterns were each common to some species. Improvements in breeding performance occurred across all three farmland types for four declining species. Grazing farmland seems to have deteriorated as breeding habitat for Linnet and arable/mixed farmland for Reed Bunting. Mixed farming at the territory scale supported better breeding performance for four species, three of which (Bullfinch, Yellowhammer and Corn Bunting) have declined concurrently with mixed farming. Pastoral landscapes supported better breeding performance for up to seven species, six of which have undergone large declines. Arable landscapes supported better breeding only for the stable or increasing Chaffinch and Greenfinch. Different relationships between farming regime and breeding performance were found at the two scales considered.  相似文献   

19.
Declines in habitat quality through the breeding season within a bird's home-range can limit overall productivity. In environments where multiple breeding opportunities arise during the course of a season, these effects can be buffered by a shift to different breeding sites or habitats. We studied the distribution and habitat associations of a crop-nesting farmland bird, the Yellow Wagtail Motacilla flava , across an arable-dominated farming region in eastern England using both field-scale territory mapping and large-scale transect surveys. Surveys were repeated at monthly intervals to measure changes in both distribution and habitat use during the course of the season. The distribution of breeding birds changed markedly at both regional and field-scales, coinciding with a shift in crop preference. Initially, most territorial birds were recorded in autumn-sown cereal fields, but this crop was subsequently abandoned in favour of potato crops, which were more patchily distributed. Other habitat features influencing Yellow Wagtail distribution included local crop diversity, hedgerow presence and soil type, with organic soils supporting higher abundance than alluvial clays or silts. The mid-season switch in habitat associations might allow individuals to maximize the number of breeding attempts made in a single year by using multiple habitats sequentially. The use of multiple habitats could influence population regulation by buffering the effects of local within-season declines in habitat suitability. Seasonal habitat switching may be more prevalent than is currently recognized in seasonal environments.  相似文献   

20.
Capsule Declines in the breeding populations of Snipe, Lapwing and Curlew were recorded between April and June 1999 and compared with previous estimates in 1987.

Aims To compare populations of non-coastal breeding waders between 1987 and 1999.

Methods In 106 2 km × 2 km square tetrads, observers recorded the number of breeding pairs of waders and habitat details on 1:10 000 scale maps.

Results A significant decline of c. 60% for Lapwing and Curlew, and a non-significant decline of 30% for Snipe was recorded over 12 years. Concentrations of these species were found in County Tyrone, but Counties Antrim, Down and Armagh supported few breeding pairs of any species. Very few pairs of any species were recorded on improved grassland despite its widespread availability.

Conclusion A successful conservation strategy for these species must address the wider countryside and not just key sites. Intensive pastoral farming in upland and lowland areas and activities such as drainage and peat extraction will further reduce the suitability of open habitats for these wader species.  相似文献   

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