Population trends of brown hares in Switzerland: The role of land-use and ecological compensation areas

Over the last decades, agricultural land-use practices have been intensified throughout Europe. As a consequence of the resulting loss of habitat heterogeneity, numerous species associated with traditional farmland have undergone severe population declines. To mitigate the negative effects of intensive agriculture on farmland biodiversity, agri-environment schemes (AES) have been adopted in various European countries since the early 1990s. The effects of AES have been evaluated for different taxa, but rarely for larger mammals like the brown hare (Lepus europaeus), a characteristic species of traditional open farmland.Using spotlight counts from 58 brown hare monitoring study sites over 17 years, we analysed the effects of land-use and several agri-environment scheme options on brown hare density in the Swiss lowland. We used open-population binomial mixture models to jointly model abundance and detection probability, thereby accounting for imperfect detection of hares.Mean observed counts of brown hares in Switzerland from 1992 to 2008 suggested a slight decline followed by a recovery in arable study sites, whereas a sustained decline was apparent in grassland sites. Mean detection probability ranged widely from year to year (arable: 0.33–0.70; grassland: 0.21–0.80). When accounting for imperfect detection, a population recovery was apparent in both land-use types, although hare densities remained at low levels compared to other European countries.The amount of extensively managed hay meadows seemed to have a positive effect on brown hare abundance both in arable and grassland sites. Hedgerows were also positively related to hare density, although only in arable study sites. The amount of set-asides/wildflower strips and brown hare density were related neither in arable nor in grassland sites. This result was probably caused by the fairly low percentages of this AES option in our study sites.Habitat improvements by means of AES indicate some positive effects on brown hare populations in Switzerland, but the quantity and quality of AES must still be increased. Combined with a binomial mixture model correcting for imperfect detection, spotlight counts are an effective tool for estimating population trends, especially for large-scale and long-term surveys like the Swiss brown hare monitoring.     

Modeling the reintroduction of lynx to the southern portion of its range

We modeled populations of lynx (Lynx canadensis) and snowshoe hares (Lepus americanus) to determine prey densities required for persistence of lynx translocated to the southern portion of the species' range. The models suggested that a density of 1.1-1.8 hares/h is required for lynx persistence; these densities are higher than those reported for most hare populations across the USA. We found that lynx dispersal and density-independent mortality substantially increased the hare density required for lynx persistence. Reintroduction success was associated with number of release events, total number of animals released, and timing of release relative to the phase of the hare population cycle. However, no release protocol could override the negative effects of low prey density or high population losses. We conclude that successful lynx reintroduction requires high hare densities and minimal anthropogenic disturbance; few areas in the contiguous USA currently posses such qualities.     

Habitat relations of Rhea americana in an agroecosystem of Buenos Aires Province, Argentina

The maintenance of wild populations of Greater Rhea (Rhea americana) through effective management requires an understanding of their habitat requirements in terms of vegetation composition and field configuration. We studied the relative influence of some anthropogenic variables (presence of route, house and fences) and resource variables (presence of water source, composition and coverage of plant species, vegetation height and bare soil), on the habitat use by a population of rheas in a cattle ranch of Buenos Aires Province, Argentina. Habitat use was determined indirectly by documenting the number of faeces in summer, autumn-winter and spring 1999. The presence or absence of faeces was related to the measured variables through discriminant analysis that allowed the elaboration of predictive models of habitat use by this species. Contrary to what was expected, those variables related to human activity showed a low predictive value on the habitat use by rheas when compared with resource variables. Rheas preferentially selected the stream area in all seasons and sites with great percent cover of Bupleurum sp., Phyla canescens, Sida leprosa, Plantago lanceolata, Trifolium repens, Lolium multiflorum, Stipa spp., and Stenotaphrum secundatum. Low vegetation height was another important component of rhea's habitat in summer and autumn-winter. The high accuracy level obtained by validation tests of this model supports its utility for the management of rhea populations in other cattle ranches of the region, and to analyze the suitability of other ranches for reintroduction programs.     

Habitat use and conservation of bumblebees (Bombus spp.) under different grassland management regimes

Declines in the natural populations of several bumblebee species across Britain and Europe are an increasing cause for concern. In this study the habitat use of bumblebees was investigated on Salisbury Plain Training Area, the largest remaining area of unimproved chalk grassland in north-west Europe. Habitat characteristics influencing the overall abundance, species richness and foraging activity of bumblebees included the diversity and abundance of flowering plant species (particularly of favoured forage plants such as Trifolium pratense), vegetation structure and height. It is suggested that different Bombus species respond to these habitat characteristics depending on their specific foraging and nesting requirements, the case of Bombus humilis being especially relevant. The effects of several grassland management practices were considered in terms of their suitability for the conservation of bumblebee habitats. Cattle grazing was shown to be preferable to both sheep grazing and the absence of any management, although the timing and intensity of such grazing was important. Small-scale disturbances caused by vehicle activity were also of value in producing locally abundant forage resources in less intensively managed grasslands.     

Building large-scale spatially explicit models to predict the distribution of suitable habitat patches for the Greater rhea (Rhea americana), a near-threatened species

We developed large-scale spatially explicit models to predict the distribution of suitable habitat patches for the Greater rhea (Rhea americana), a near-threatened species, in two areas of central Argentina with different land use: a grassland area (ca. 4943 km²) mainly devoted to cattle grazing and an agro-ecosystem area (ca. 4006 km²) mostly used for crop production. The models were developed using logistic regression and were based on current records of Greater rhea occurrence coupled with remote sensing data, including land cover and human presence variables. The habitat suitability maps generated were used to predict the suitable habitat patch structure for wild rhea populations in each area. Fifty-one percent of the total grassland area was suitable for the species, being represented by a single large patch that included 62% of the individual locations. In the agro-ecosystem, only 28% of the total area was suitable, which was distributed among four patches. Seventy percent of rhea observations were in suitable habitat, with all rheas grouped in the largest patch. Conservation efforts for preserving wild rhea populations should be focused on maintaining habitats similar to grasslands, which are less profitable for landowners at present. Consequently, the protection of the pampas grasslands, a key habitat for this species as well as for others with similar habitat requirements, will demand strong conservation actions through the reconciliation of interests between producers and conservationists, since the proportion of croplands is increasing.     

Habitat associations of bats in Northern Ireland: implications for conservation

Agricultural intensification in Northern Ireland has brought about large-scale changes to the landscape with a detrimental effect on biodiversity. Between 1996 and 1998, we surveyed a stratified random sample of 1 km squares for bats using a spot-sample technique and time expansion bat detector to establish linear and area habitat associations. Bats strongly selected water bodies with bankside vegetation, treelines, and deciduous and mixed woodland edge, avoiding open areas such as upland/unimproved grassland and improved grassland. Of three sympatric pipistrelle species (Pipistrellus pipistrellus, P. pygmaeus and P. nathusii), two were shown to forage in different habitats; P. pipistrellus being more of a ‘generalist’, foraging in a wider variety of habitats than P. pygmaeus, a ‘specialist’ which foraged in a smaller range of habitats. Nyctalus leisleri selected parkland/amenity grassland, deciduous woodland edge and rivers/canals and avoided improved grassland, hedgerows, whilst Myotis spp. selected deciduous woodland centre, lake/reservoir margins and rivers/canals. Reduction in area and quality of inland water, deciduous woodlands and field boundaries in Northern Ireland may impact on bat populations. Habitat management should focus on improving those habitats which are selected by bats, including the maintenance and enhancement of connecting linear habitats.     

Nitrous oxide emissions from fertilised grassland: A 2-year study of the effects of N fertiliser form and environmental conditions

The aim was to investigate the effects of different N fertilisers on nitrous oxide (N₂O) flux from agricultural grassland, with a view to suggesting fertiliser practices least likely to cause substantial N₂O emissions, and to assess the influence of soil and environmental factors on the emissions. Replicate plots on a clay loam grassland were fertilised with ammonium sulphate (AS), urea (U), calcium nitrate (CN), ammonium nitrate (AN), or cattle slurry supplemented with AN on three occasions in each of 2 years. Frequent measurements were made of N₂O flux and soil and environmental variables. The loss of N₂O-N as a percentage of N fertiliser applied was highest from the supplemented slurry (SS) treatment and U, and lowest from AS. The temporal pattern of losses was different for the different fertilisers and between years. Losses from U were lower than those from AN and CN in the spring, but higher in the summer. The high summer fluxes were associated with high water-filled pore space (WFPS) values. Fluxes also rose steeply with temperature where WFPS or mineral N values were not limiting. Total annual loss was higher in the 2nd year, probably because of the rainfall pattern: the percentage losses were 2.2, 1.4, 1.2, 1.1 and 0.4 from SS, U, AN, CN and AS, respectively. Application of U in the spring and AN twice in the summer in the 2nd year gave an average emission factor of 0.8% – lower than from application of either individual fertiliser. We suggest that similar varied fertilisation practices, modified according to soil and crop type and climatic conditions, might be employed to minimise N₂O emissions from agricultural land. Received: 30 August 1996     

Population ecology of the Chinese grouse, Bonasa sewerzowi, in a fragmented landscape

We report the first population ecology study of the endangered Chinese grouse (Bonasa sewerzowi). The study population was stable during 1995-2000. Annual rates of survival were 0.64 for adults and only 0.17 for chicks to 13 weeks of age. Reproductive parameters were 6.1 eggs/clutch, 63% nest success, and overall 3.6 chicks hatched/female/year. The spring sex ratio was 64% males, with 44% of the males unmated in spring. Local people found an estimated 10-29% of the nests and took the eggs for food. Only about 9% of the reserve containing the study area is mature mixed forest, the preferred habitat. Inadequate brood habitat may have influenced chick survival and the skewed adult sex ratio may be a result of habitat fragmentation. We recommend protecting the remaining mixed forest, creating more brood habitat, and stopping the taking of eggs.     

Higher breeding densities of the threatened little bustard Tetrax tetrax occur in larger grassland fields: Implications for conservation

Previous studies have found that densities of little bustard Tetrax tetrax breeding males tend to be higher in areas with smaller agricultural fields, presumably due to increased habitat diversity. However, exceptionally high densities have been found in large grassland fields in Portugal, which suggests that the influence of field size varies geographically, and that the role of this factor is not yet fully understood, despite its importance as a key management issue.We studied how field size, together with vegetation structure, influences the presence and density of breeding little bustards in a region of southern Portugal. Fifty-four grassland fields were sampled in 2007 and another 29 in 2008, with sizes ranging from 23 to 172 ha. A total of 183 breeding males were found in 47 of these fields, reaching densities of up to 37 males/100 ha. A higher probability of occurrence of breeding males was found in larger fields with a vegetation height below 40 cm and field size alone explained 46% of the variability in male density. These results suggest that larger continuous areas of suitable habitat attract many males, most likely as a consequence of their lek mating system. We conclude that conservation efforts, in a landscape context of large farm sizes, should: (1) be channelled to farms with large fields; (2) ensure adequate livestock grazing to create suitable habitat and (3) promote management at a landscape level to ensure the most continuous grassland habitat patches possible.     

Post-dispersal fate of hazel (Corylus avellana) nuts and consequences for the management and conservation of scrub-grassland mosaics

Granivorous rodents and birds are both predators and dispersers of the nuts produced by many woody plants. This study examines the role of granivores as predators and dispersers of Corylus avellana L. and the consequences of this interaction for Corylus regeneration and scrub encroachment into grassland. In the Cressbrook Dale nature reserve (Derbyshire, UK), Corylus nuts were buried in the grassland at two distances (<15 and >70 m) from scrub vegetation (the main source of nuts, and habitat of the granivores) to estimate the rate of seed removal over 3 years, assessing also the success of dispersal and seedling establishment in the grassland. The rate of nut removal at close sites (<15 m from scrub) was consistently higher than at far sites (>70 m) over the 3 years. All sown nuts were removed over 2 years at close sites, while at the far sites around 20% of the sown nuts were still present the following spring. Grassland close to the scrub had the highest intensity of nut predation but also had the highest density of Corylus seedlings. Sciurus carolinensis was the most important disperser of hazelnuts into the grassland. This squirrel scatter-hoarded 10-12 thousand hazelnuts in 1.5 ha of grassland adjacent to scrub. In this reserve, two vertebrates - both non-native - are largely responsible for maintaining the dynamic balance between the scrub and grassland habitats. American grey squirrels disperse hazelnuts into the grassland and sheep slow the encroachment of scrub by repeated browsing.     

Remaining large grasslands may not be sufficient to prevent grassland bird declines

Grassland birds are in steep decline throughout many regions of the world. In North America, even some common species have declined by >50% over the last few decades. Declines in grassland bird populations have generally been attributed to widespread agricultural conversion of grasslands; more than 80% of North American grasslands have been converted to agriculture and other land uses, for example. Remaining large grasslands should thus be especially important to the conservation of grassland birds. The Flint Hills of Kansas and Oklahoma (USA) preserves the largest intact tallgrass prairie (∼2 million ha) left in the world. The Flint Hills supports a major cattle industry, however, and therefore experiences widespread grazing and frequent burning. We assessed the regional population status of three grassland birds that are considered the core of the avian community in this region (Dickcissel, Spiza americana; Grasshopper Sparrow, Ammodramus savannarum; Eastern Meadowlark, Sturnella magna). Our approach is founded on a demographic analysis that additionally explores how to model variability in empirically derived estimates of reproductive success across a large heterogeneous landscape, which ultimately requires the translation of demographic data from local (plot) to regional scales. We found that none of these species is demographically viable at a regional scale under realistic assumptions, with estimated population declines of 3-29%/year and a likelihood of regional viability of 0-45% over the two years of study. Current land-management practices may thus be exacerbating grassland bird declines by degrading habitat in even large grassland remnants. Habitat area is thus no guarantee of population viability in landscapes managed predominantly for agricultural or livestock production.     

Influence of roads on the endangered Stephens' kangaroo rat (Dipodomys stephensi): are dirt and gravel roads different?

Roads can have major impacts on animal distribution and movement patterns by destroying or creating habitat, and by acting as both barriers and corridors for movement. Using a combination of live trapping and spool and line tracking, we compare the relative abundance, mass, and demographic turnover of the endangered Stephens' kangaroo rat (Dipodomys stephensi) on dirt and gravel roads in comparison with adjacent grassland habitat. D. stephensi was more active on dirt roads, and less so on gravel roads, relative to adjacent grassland habitat. Dirt roads were used extensively, and animals tended to move greater distances along dirt roads than in surrounding grasslands. In contrast, gravel roads were used much less extensively than adjacent grasslands. Animals using dirt roads were significantly lighter in mass than those on gravel roads and in adjacent grassland, suggesting greater use by juvenile animals. Dirt roads also had lower rates of recapture and higher rates of new arrivals than did adjacent habitat. These findings suggest that dirt roads provide potentially important landscape linkages for D. stephensi, whereas that gravel roads may act as movement barriers.     

Status, distribution and definition of mycologically important grasslands in Scotland

In northern Europe, unimproved grasslands provide the habitat for a diverse group of fungi, including members of the genera Camarophyllopsis, Hygrocybe, Entoloma and Dermoloma, and the families Clavariaceae and Geoglossaceae. These fungi are currently the focus of international conservation concern, owing to rapid declines in the availability of suitable habitat. To assess their status in Scotland, 621 field surveys were undertaken on a total of 511 sites, distributed throughout the country. Taxa were found to differ substantially in abundance; for example, whereas five Hygrocybe taxa were recorded at a single site, seven taxa were recorded on more than 200 sites. The number of Hygrocybe taxa per site was found to be positively correlated with number of Clavariaceae taxa (r=0.60); however, the total number of Entoloma taxa was poorly correlated with diversity of other groups (r<0.35). Detrended correspondence analysis (DCA) of field data highlighted variation in composition of fungal communities; in particular, Entoloma taxa were found to cluster together, and were rarely found in association with Geoglossaceae. The data were used to critically examine current approaches to defining the conservation importance of grassland sites on the basis of their mycota. Species accumulation curves indicated that more than 16 visits may be required to fully characterize the fungal diversity of a site. Different groups of fungi also displayed constrasting patterns of seasonal variation in sporome production; peak diversity values for Geoglossaceae and Clavariaceae tended to occur later in the year than for Hygrocybe and Entoloma. Such results indicate that intensive, multiple surveys over prolonged periods are required to accurately define the conservation value of grassland sites. However, these preliminary data suggest that the unimproved grasslands of Scotland are of exceptional importance for fungal conservation, compared with other countries of northern Europe.     

Grasslands as movement barriers for a forest-associated salamander: Migration behavior of adult and juvenile salamanders at a distinct habitat edge

The persistence of amphibian populations in fragmented landscapes requires dispersal and recolonization of habitat patches after local extinction. These processes entail individuals crossing habitat edges. Edge permeability integrates the behavior of individuals with the vegetative structure of the habitat edge and may influence the dispersal rates between habitat patches. We used drift fences, radio telemetry, and an experimental displacement to examine the movement behavior of juvenile and adult spotted salamanders (Ambystoma maculatum) at a pond located in continuous forest and a pond located on a distinct forest-grassland edge. At the pond on the habitat edge, adult salamanders migrated to and from the forested side of the pond. Resident adults with transmitters migrated to forested habitat without approaching the habitat edge. Displaced adults with transmitters halted emigration movements when they approached the habitat edge. None of the radio-tagged adults were observed more than a few meters into the grassland. Recently metamorphosed juveniles exiting the grassland side of the pond changed their direction of movement and migrated into the forested habitat. We conclude that salamanders oriented movements with respect to features in the terrestrial habitat, detected the habitat edge, and behaviorally avoided the grassland. Exploring the permeability of habitat edges will improve our understanding of dispersal within fragmented landscapes and enhance efforts to conserve regional populations of amphibians.     

Nest site restoration increases the breeding density of blue-tailed bee-eaters

For birds that excavate their own nest burrows, the availability of suitable nest sites and substrates may influence the number and density of breeding birds. However, few studies of burrow-nesting birds have experimentally manipulated nest site or substrate availability. The blue-tailed bee-eater (Merops philippinus) is a colony breeding, summer migrant that excavates nest burrows in sandy banks on Kinmen Island, 5 km east of mainland China. To test whether substrate availability influenced the density or reproductive success of breeding pairs of bee-eaters, we removed all vegetation and old nest holes on treated slopes and left control slopes unmanipulated in 2003 and 2004. Plant cover on control slopes was 37.7% (11.9-67.7%). Slope gradient, soil penetration resistance and vegetation height in front of slopes did not differ between treated and control slopes in either year. Combining data from both years, the density of active nests was significantly higher (3.1-fold) on treated slopes than on control slopes. However, the reproductive performance of bee-eaters nesting on treated and control slopes did not differ in either year. Thus, removing vegetation and old nest holes from slopes with sandy loam soil improved the breeding habitat and increased the number of breeding blue-tailed bee-eaters. This technique could be used to support and manage populations of this species and other burrow-nestling species with similar habitat requirements.     

Habitat and flower resource partitioning by an exotic and three native bumble bees in central Hokkaido, Japan

Studies of the interspecific relationships between alien and native pollinator species can help forecast the success of alien species as well as assess the extent of disturbance to native plant-pollinator interactions. We examined the habitat and flower resource occupancy by the invasive introduced bumble bee Bombus terrestris and three dominant native bumble bees in central Hokkaido, northern Japan, in relation to a landscape factor (forest cover ratio) and flower morphology with respect to the proboscis length of bees. Three years of monitoring the invasive boundary of B. terrestris indicated that this species, which dominates open agricultural areas, probably will not invade the forests in which the native species dominate. This habitat partitioning likely followed the displacement of the natives by the invader in open agricultural lands. In forested areas, the native species partitioned flower resources on the basis of the relationship between proboscis length and the lengths of the corolla tubes of flowers. However, in open agricultural areas, both the long- and short-tubed flowers were primarily visited by the exotic short-tongued B. terrestris, which foraged illegitimately (by nectar robbing) on long-tubed flowers (Trifolium pratense L.) and legitimately on short-tubed flowers (T. repens L. and Lavandula angustifolia Mill.). The invasion of B. terrestris into open natural vegetation, in addition to open agricultural areas, has recently been reported in Hokkaido. Even though the exotic and dominant native bumble bees partition their habitat according to landscape factors, the invasive bee has the potential to alter the overall interactions within plant-pollinator systems in the regions of open vegetation on Hokkaido Island.     

Habitat selection and conservation of Sharpe's longclaw (Macronyx sharpei), a threatened Kenyan grassland endemic

Montane grassland is a severely threatened habitat in Kenya. Despite a high level of faunal endemism, it has received very little conservation attention. We investigated habitat selection in a threatened grassland endemic bird species, Sharpe's longclaw (Macronyx sharpei) (family Motacillidae), in order to understand its likely response to land-use changes. Between November 1995 and May 1996, we studied 41 territories of this species on the Kinangop Plateau in central Kenya. With an overall density of 0.4 birds ha⁻¹, longclaws lived in permanent groups of two to seven individuals. They were sedentary and territorial, with a mean home range size of 0.5 ha. The species avoided non-grassland areas entirely, and within grassland showed a strong preference for short grass with tussocks. Territory sizes and foraging ranges were smaller, and rates of pecking for food higher, in this grassland type than in open short grass or long grass. Land use changes, in particular conversion to cultivation or woodlots and ploughing up of grassland to remove tussocks, pose a serious and immediate threat to this species. Dairy farming is potentially compatible with grassland conservation, and conservation-friendly livestock rearing needs to be promoted through economic incentives, awareness-raising and technical advice.     

新疆伊犁荒漠草原恢复措施下植物群落生态位特征分析

以禁牧2 年、休牧(每年5 月底至10 月初)、补播杂花苜蓿2 年3 种恢复措施及处于自由放牧状态下的荒漠草原退化草地为研究对象, 分析了伊犁荒漠草原植物群落的生态位特征。结果表明: 在对照、禁牧、休牧样地中, 建群种伊犁绢蒿(Seriphidium transiliense)生态位宽度值最大, 分别为1.037、1.101 和1.070, 在补播样地中针茅(Stipa sp.)的生态位宽度值最大, 为0.798。较高的生态位重叠发生在生态位宽度较大的物种之间,但最大的生态位重叠发生在生态位宽度较小的物种之间。在4 种样地中, 伊犁绢蒿-角果藜(Ceratoides arenarius)之间存在较高的生态位重叠和较大的生态位相似比例, 证明2 个种群之间在资源利用上存在激烈的种间竞争。     

Slurry field management and ammonia emissions under Mediterranean conditions

In Spain, farmers are interested in applying pig (Sus scrofa domesticus) slurry (PS) to their fields throughout the year. During the spring and summer months, ammonia (NH₃) volatilization may be high. We studied the potential range of NH₃ losses under a warm and a hot period of the year, using available field practices, and two strategies: PS directly incorporated into the soil, in spring (I‐spring); and PS applied by splash‐plate, in summer time (SP‐summer), both to bare soil. Measurements were conducted, after PS application, using the micrometeorological mass balance integrated horizontal flux method. The cumulative NH₃‐N volatilization was 35% (I‐spring) and 60% (SP‐summer) of total ammonium nitrogen applied, and half of the total NH₃‐N losses happened by 17 h and 8 h, respectively, after application. Incorporation strategy was less effective in avoiding NH₃ losses than is described in the literature. This fact has important consequences for the implementation of NH₃ mitigation measures in Mediterranean agricultural systems.