A survey of natterjack toad Bufo calamita distribution and breeding success in the north merseyside sand-dune system,England

In spring 1978, adult natterjack toads Bufo calamita assembled at 101 out of 132 sites containing water in the north Merseyside sand-dunes. A total of 2001 spawn strings was counted in 95 sites, 95% of the spawn being deposited before 11 May. Metamorphosis was confirmed at 28 sites and probably occurred at a further 12 sites distributed throughout the dunes. Most spawning took place in shallow water in slacks or excavated scrapes. Deep ponds, ditches and bomb craters were little used. Unsuccessful breeding was mainly due to shallow water bodies drying up before metamorphosis could occur. Of sites where metamorphosis was confirmed, 82% were scrapes which had been excavated for conservation purposes.Water-table trends in the dune system and various methods of censusing the adult toad population are discussed.     

A review of scientific information pertaining to the natterjack toad Bufo calamita throughout its geographical range

The biology of the natterjack toad Bufo calamita is reviewed with special regard to studies of the species which have been carried out over the last 30 years. Aspects considered include distribution, habitat, species status, behaviour, physiology and autecology. The value of the information to conservation management is discussed.     

Climatic effects on calling and spawning of the natterjack toad Bufo calamita: Discriminant analyses and applications for conservation monitoring

Unlike the other anurans native to Britain, the rare natterjack toad Bufo calamita has a protracted breeding season. Surviving populations are regularly monitored for assessment of population trends and conservation requirements. We have examined the factors influencing calling and spawning behaviour at two British sites and used discriminant analysis to identify climatic conditions associated with reproductive activity. These conditions include rainfall over a short period preceding spawning, though not necessarily on the day itself, and preferably following a spell of dry weather; maximum temperatures on the day before spawning of at least 10°C, and a series of preceding minimum temperatures of at least 5°C (on average) over 2–4 nights. We anticipate that this kind of climatic information, which is accessible without actually visiting toad sites, should maximise the efficiency of monitoring operations by allowing judicious use of limited resources.     

The status and conservation of the butterfly Plebejus argus L. (Lepidoptera: Lycaenidae) in North West Britain

A survey was made of the declining butterfly, Plebejus argus L., in North West Britain in 1983. Twenty-six colonies were found on limestone grassland, many of them large. Twenty colonies were found on heathland, but most were relatively small. One large colony that inhabits mossland was rediscovered. P. argus occupies early succesional habitat at low altitude, predominantly on sheltered southerly facing slopes. Through biotope loss and fragmentation and declining traditional management, suitable habitat is created only sporadically in modern Britain. Some of these habitats (especially on heathland) are short lived. Thus, many colonies are transient. As P. argus forms closed colonies and rarely flies far, the decline appears to be a compound effect of reduced amounts of suitable habitat and inability to colonise them: the distances are often too great. Active conservation is required to check the decline of P. argus, especially habitat management and also introduction to suitable habitat now beyond the dispersal range of P. argus. Recommendations are made.     

Declines in forage availability for bumblebees at a national scale

We assessed national scale changes in the forage plants of bumblebees in Britain, as a means of providing quantitative evidence for the likely principal cause of declines in bumblebee species. We quantified the relative value of native and long-established plant species as forage (nectar and pollen) resources for bumblebees by collating visitation data from 14 field sites across Britain. Twentieth Century changes in range and frequency of these forage plants were assessed using data from the New Atlas of the British and Irish Flora (1930-1969 to 1987-1999) and the Countryside Surveys of Britain (1978-1998). Forage plants declined in both large-scale range and local-scale frequency between the two survey periods. These changes were of greater magnitude than changes in other native plant species, reflecting serious reductions in quality of foraging habitats for bees as well as a general decline in insect-pollinated plants. Seventy-six percent of forage plants declined in frequency within 1-km squares, including those (e.g. Trifolium pratense) of particular value for threatened bumblebee species. We consider how our findings relate to other recorded changes in the British flora, how they may help to explain declines in bumblebees and how they could contribute to a conservation strategy.     

Recent, substantial, and unexplained declines of the common toad Bufo bufo in lowland England

A decline in numbers of a large common toad (Bufo bufo) population in south-east England during the 1990s, together with anecdotal reports of similar trends in other toad populations, prompted a nation-wide survey of this species. The survey also included the common frog (Rana temporaria) as a control for which there was no comparable evidence of recent decline. A questionnaire requesting information on the fate of toad and frog populations in the last 15 years of the 20th century was distributed to professional and amateur herpetologists during autumn 2001. Ninety-five respondents provided data on a total of 277 sites, including 232 frog and 202 toad populations in England, Scotland and Wales. More than 80% of the reported sites were rural for both species. Rural frog populations were generally doing well in most parts of Britain, with almost as many increasing as decreasing populations and a high proportion of stable populations. Rural toads also showed no overall trend across the country as a whole. However, regional analysis indicated that although toads were faring at least as well as frogs in the north and west of Britain, they were declining seriously in central and eastern/south-eastern areas. In these regions 50% or more of toad populations have experienced recent declines, whereas frogs have fared as well as they have elsewhere. Toads breeding alone have fared significantly worse than toads breeding at sites where frogs were also present. Reasons for apparently toad-specific declines in lowland England remain unknown.     

The potential for lowland heath regeneration following plantation removal

Historical records show that large areas of lowland heath have been planted with coniferous woodland. Such sites will increasingly be targeted for heathland restoration in order to achieve the objectives set by current conservation policy. Therefore information on management to achieve effective restoration is a priority for research. In this study we examined the size, composition and distribution of the seed bank beneath conifer plantations of different ages at two important heathland sites in Britain. Changes in the physical and chemical properties of heathland soil under the plantations were also described. There were significant, exponential declines in the mean density of viable heather seeds with plantation age at both sites. However, relatively large seed banks survived for 40 years and under some circumstances for more than 70 years, suggesting that restoration on first rotation sites is unlikely to be seed limited. There were small, but significant differences in the soil nutrient status under the plantations compared to the adjacent heaths. It was concluded that the main constraint on heathland regeneration is likely to be the burial of the seed bank by a thick layer of conifer leaf litter. The mechanical removal of this layer has been shown to be practically feasible.     

Re-creation of heathland on improved pasture using top soil removal and sulphur amendments: Edaphic drivers and impacts on ericoid mycorrhizas

Understanding the factors that drive successful re-creation and restoration of lowland heaths is crucially important for achieving the long-term conservation of this threatened habitat type. In this study we investigated the changes in soil chemistry, plant community and interactions between Calluna vulgaris and symbiotic ericoid mycorrhizas (ERM) that occurred when improved pasture was subjected to one of three treatments (i) acidification with elemental sulphur (ii) acidification with ferrous sulphur (iii) removal of the topsoil. We found that the soil stripping treatment produced the greatest reduction in available phosphate but did not decrease soil pH. Conversely, acidification with elemental sulphur decreased pH but increased availability of phosphate and potentially toxic cations. The elemental sulphur treatment produced plant communities that most closely resembled those on surrounding heaths and acid grasslands. The most important driver was low pH and concomitant increased availability of potentially toxic cations. Plant community development was found to be little related to levels of available soil phosphate, particularly at low pH. The elemental sulphur treatment also produced the best germination and growth of C. vulgaris over 4-5 years. However, this treatment was found to inhibit the development of symbiotic relationships between C. vulgaris and ERM. This may affect the long-term persistence of re-created vegetation and its interactions with other components of heathland communities.     

Impacts of grazing on montane heath vegetation in Wales and implications for the restoration of montane areas

The impact of long-term heavy grazing pressure on montane vegetation and soils was investigated on the Carneddau plateau in North Wales. At this site, historical information suggests that formerly extensive Racomitrium- and Vaccinium-dominated heaths have become degraded and reduced in extent over the last 40-50 years. This coincides with a period when both sheep numbers and atmospheric deposition of nitrogen have greatly increased. Vegetation composition, plant tissue chemistry, soil chemistry and sheep presence were compared between areas of ‘good’ condition Racomitrium and Vaccinium heath and degraded areas. Comparison of species composition data with sheep presence and environmental data showed no significant link between current grazing distribution and species composition in the areas investigated, with all habitats having sheep presence above the recommended maximum for this habitat. Soil chemistry showed several differences between degraded and ‘good’ condition habitats, suggesting that degraded areas had experienced loss of soil organic matter and upper organic horizons. Comparison of soil and vegetation nitrogen content with data from other UK sites suggests a build up of nitrogen has occurred in Carneddau vegetation and soils, possibly related to high levels of nitrogen deposition. It is concluded that restoration of severely degraded areas of montane vegetation may be retarded by deleterious changes in soil properties which could slow recolonisation by montane species. Reductions in stocking density aiming to restore montane communities might have more immediate impact on less degraded areas.     

Population declines of the magpie Pica pica in Huntingdonshire and other parts of eastern England

Since the second world war, the magpie Pica pica is known to have suffered population declines in parts of eastern England. To understand more fully the reasons for these declines, the status and fate of the magpie population in the County of Huntingdonshire (now part of Cambridgeshire) have been examined in detail.Some decline occurred prior to the mid 1950s, associated with changes in habitat. During the late 1950s and early 1960s, the breeding population decreased markedley to perhaps about 5% of its pre-war level. Mortality caused by dieldrin and other cyclodiene insecticides was the most likely single cause of this sudden decline. The population remained at a low level until about 1974. Since then there has been some recovery although the magpie is still relatively rare. Failure to recover more rapidly may be linked with the sedentary nature of this species precluding any significant recovery via immigration.     

The importance of former land use in determining successful re-creation of lowland heath in southern England

In order to reverse losses of lowland heathland substantial areas of former agricultural and forestry land are currently being targeted for restoration. In this study we assessed the success of heathland re-creation on 37 former arable, improved grassland and conifer plantation sites in southern England, UK. The similarity between the vegetation and seed banks of the re-creation sites and undisturbed heathland controls were examined in relation to former land use, soil properties and re-creation management. Former land use was found to be the most important determinant of re-creation success. On former arable, and to a lesser extent improved grassland, antecedent management had caused significant changes to seed bank and soil properties. As a result, regeneration of Calluna heath had been minimal, even on sites where appropriate management (e.g. cropping, addition of pH amendments) had been undertaken and heathland species introduced. In contrast, former plantation seed banks and soils were similar to heathland controls, and, as a result, rapid regeneration of Calluna heath had taken place. It was concluded that conifer removal provides the most practical and cost-effective means of re-creating Calluna heath on former heathland, although further research is required to assess the effect of litter removal and the rate at which heather seed banks decline following conversion to forestry. In contrast, re-creation on former agricultural sites will require effective management to reduce soil pH, fertility and the abundance of competitive species as well as the introduction of heathland propagules. Given limited resources a more realistic objective for these sites is likely to be reversion to an acid grassland or grass-heath.     

Rehabilitation of degraded dry heather [Calluna vulgaris (L.) Hull] moorland by controlled sheep grazing

Many areas of heathland in Europe have seen a decline in the area and condition of Calluna vulgaris (heather)-dominated vegetation, with subsequent declines in the associated faunal interest. Grazing, alongside burning, is still the predominant means of managing heathland vegetation, and, therefore, it is by manipulating this management that cost-effective improvements in vegetation condition can be made. This paper investigates the suitability of different grazing treatments for rehabilitating degraded ‘dry heath’. Treatments varied in the intensity (0-1.9 sheep ha⁻¹ year⁻¹) and timing (summer vs. winter) of sheep grazing. These treatments were compared with the behaviour of vegetation outside the fenced area kept under the previous management (open access all year round). As rabbits were common on the site, fences were erected to prevent access to the sheep grazed plots. Vegetation composition remained stable outside the fenced area, whilst all the fenced treatments showed a decrease in heather utilisation and an increase in the relative frequency of heather over the 5 years of the experiment. The increase was in proportion to the reduction in stocking rate, with only slow increases in relative frequency observed in the high grazing treatments (winter and summer). Other species that benefited from reducing grazing included Empetrum nigrum and Vaccinium myrtillus, whilst declines were observed for Agrostis capillaris and total monocotyledonous species. Only small overall differences were observed between the winter low, summer low and no sheep grazing treatments. However, a difference in response was present between the sheep exclosures and the sheep+rabbit exclosures, indicating that rabbits were having a noticeable effect on heather recovery at this site. On this degraded ‘dry heath’ system, imposing a reduction in stocking density improved the condition of the dwarf shrubs present and reduced the grass component of the vegetation. There was little effect of the timing of grazing, such that a reduction in sheep numbers to 0.8/0.9 sheep ha⁻¹ year⁻¹, to give utilisation levels of below 20%, can achieve the desired result of improving vegetation condition whilst still achieving some economic return from grazing. However, the wide range of ‘sustainable’ stocking densities for different heathland systems highlights the need to base effective management on measured utilisation rather than on stock numbers.     

The buffer effect of non-breeding birds and the timing of farmland bird declines

Breeding territoriality in birds means that a certain proportion of the adult population may breed in suboptimal habitats or not breed at all. Non-breeding birds, or floaters, can have a `buffer effect' on breeding population size. Farmland bird declines in Britain are measured and analysed in terms of numbers of territory-holding birds. We use a population dynamics model to illustrate how, because of the buffer effect of floaters, there can be a time lag between the start of total population decline and detectable breeding population decline. Differences in the timing of declines of closely related farmland birds could therefore be due to slight differences in their population dynamics, rather than differences in their response to agricultural change.     

Land use changes and raptor conservation in steppe habitats of Eastern Kazakhstan

Steppe habitats in central Asia have suffered important land use changes during this century which are similar to those that have been pointed out as the causes of the decline of steppe birds in western Europe. During June 1999 we conducted road surveys of raptors in Eastern Kazakhstan to detect specific and community responses to land use changes. We detected 11 species of raptors. Kestrels (Falco naumanni and tinnunculus) were the most common species in grasslands and agricultural landscapes, harriers (Circus pygargus and macrourus) were dominant in saline steppes and steppe eagles (Aquila nipalensis) were dominant in dry steppes. There were fewer species in agricultural habitats than in grassland and steppe habitats. Ground-nesting raptors were negatively affected by land use changes and four species were never detected in agricultural zones. Raptor abundance patterns differed between natural steppe habitats and human-transformed habitats, where a patchy distribution was detected. The future of raptor communities in Kazakhstan seems uncertain although the progressive abandonment of intensive agriculture may benefit species sensitive to human presence. The long-term conservation of vertebrate communities may depend upon the maintenance of ecologically and socially sustainable grazing systems.     

Rehabilitation of degraded Calluna vulgaris (L.) Hull-dominated wet heath by controlled sheep grazing

Many upland areas of the British Isles have seen declines in the area and condition of heather (Calluna vulgaris)-dominated heathland vegetation. To reverse this decline, management regimes must be designed to rehabilitate areas that have seen this decline. As most of this heathland vegetation is primarily managed by grazing, such management has to determine what stocking levels can maintain the vegetation in a desired state. This paper describes how to reverse this decline through suitable grazing management.A degraded ‘wet-heath’ system, previously grazed at 2.1 sheep ha⁻¹, was subject to a range of grazing treatments over a 5-year period. Treatments varied in intensity (0-1.4 sheep ha⁻¹) and timing (summer only, winter only, or year round) of grazing. Grazing levels were maintained at 2.1 sheep ha⁻¹ outside the fenced areas. Vegetation composition remained stable outside the fenced treatments. All the fenced treatments showed an increase in the relative frequency of the evergreen Calluna vulgaris, with the greatest increase being in the ungrazed treatment, and the least in the year round 1.4 sheep ha⁻¹ treatment. This increase was in line with a reduction in heather utilisation to relatively low and sustainable levels. Other species that benefited from reduced grazing included Carex nigra, Deschampsia flexuosa and to a lesser extent Galium saxatile and Erica tetralix, whereas a range of moss species including Hypnum jutlandicum and Rhytidiadelphus loreus were more frequent at higher grazing levels. Though the recovery of heather was similar in the two seasonally grazed treatments, the vegetation showed different overall trajectories. Winter only grazed allowed a substantial increase in the cover of the deciduous Molinia caerulea, whereas this species was kept in check by summer only grazing. A stocking level of between 0.7 and 1.4 sheep ha⁻¹ appears to be appropriate to maintain and even enhance the cover of heather on degraded wet heath. Complete removal is not necessary. Grazing restricted to the winter period is inappropriate in areas where M. caerulea occurs. Setting appropriate stocking levels to maintain the condition of the vegetation must take into account site conditions, especially the presence of species that can affect the utilisation of heather.     

Long-term heathland restoration on former grassland: The results of a 17-year experiment

European lowland heaths have declined by up to 80% due to land use change and lack of management. There has been considerable research into the restoration of this threatened habitat. However, long-term outcomes of restoration are poorly understood, especially in situations where past agricultural land use imposes severe constraints on community re-assembly. In 1989 a large-scale experiment was established to examine the effectiveness of five treatments to restore heathland on formerly productive grassland: (i) natural regeneration; (ii) herbicide application to facilitate regeneration; (iii) cultivation and application of seed-rich heathland vegetation; (iv) soil removal and incorporation of heathland topsoil; and (v) heathland translocation. After 17 years the pH of the unamended agricultural soil remained significantly higher than that of the adjacent heathland. All treatments showed different trajectories of vegetation change in the long-term. Natural colonisation by heathland species was slow due to seed limitation, resulting in formation of an acid grassland community. Heathland community assembly was not facilitated by destruction of the initial grassland with herbicide. Incorporation of topsoil had an intermediate effect on pH reduction. This may explain the subsequent failure of the plant community to assemble in the anticipated proportions, and the dominance of leguminous scrub species (Ulex spp.). Turf translocation was effective in reducing pH to the required range and restoring the heathland community in the long-term. However, this technique should only be considered as a means of ‘rescue’ when habitat destruction is otherwise unavoidable. The only practical and sustainable means of increasing heathland extent on former farmland is the application of seed-bearing vegetation cut as part of routine management. However, this technique needs refining in order to establish the full range of characteristic heathland species.     

Rarity and decline in bumblebees - A test of causes and correlates in the Irish fauna

Bees are believed to be in decline across many of the world’s ecosystems. Recent studies on British bumblebees proposed alternative theories to explain declines. One study suggested that greater dietary specialization among the rarer bumblebee species makes them more susceptible to decline. A second study disputed this theory and found that declines in British bumblebees were correlated with the size of species’ European ranges, leading to the suggestion that climate and habitat specialization may be better indicators of the risk of decline. Here we use a new and independent dataset based on Irish bumblebees to test the generality of these theories. We found that most of the same bumblebee species are declining across the British Isles, but that, within Ireland, a simple food-plant specialization model is inadequate to explain these declines. Furthermore, we found no evidence of a relationship between declines in Irish bumblebees and the size of species’ European ranges. However, we demonstrate that the late emerging species have declined in Ireland (and in Britain), and that these species show a statistically significant westward shift to the extremity of their range, probably as a result of changing land use. Irish data support the finding that rare and declining bumblebees are later nesting species, associated with open grassy habitats. We suggest that the widespread replacement of hay with silage in the agricultural landscape, which results in earlier and more frequent mowing and a reduction in late summer wildflowers, has played a major role in bumblebee declines.     

Conservation of isolated Atlantic heathlands in the Mediterranean region: effects of land-use changes in the Montseny biosphere reserve (Spain)

In the Mediterranean region, cycles of controlled burning combined with continuous grazing appear to have been an effective tool for maintaining isolated Calluna vulgaris heathlands in the form in which they occur in many places in the Atlantic region. Changes in land use and management of the mosaic of extensively exploited heathland and associated grassland over recent decades, such as bringing land into cultivation followed by its abandonment and the prohibition of fires has resulted in a process of transformation into new shrub communities with lower biodiversity. In the Mediterranean region, these changes are similar to those described in the Atlantic area, but encroachment occurs faster and could lead ultimately to afforestation by Mediterranean woodland.In a study area of 300 ha of heathland in the Spanish Mediterranean basin (specifically, in the Montseny Natural Park and Biosphere Reserve), comparison of present and former vegetation showed that shrub cover increased from 15% in 1967 to 32% in 2000. Broom (Cytisus scoparius) was the main invasive species in abandoned crop fields, whereas Mediterranean holm oak forest (Quercus ilex) increased by 18%. The surface area of fernlands doubled and C. vulgaris heathlands decreased from 35% to just 9% during the same period. Intermixed grasslands also decreased moderately and progressively from 4% to 3%.It seems probable that cycles of fires are more important in terms of shrub control and biodiversity conservation than continuous grazing alone, even at a high rate of stocking (four small ruminants per hectare per year). This encroachment process throws into relief the role that isolated habitats can play as a monitor of land use changes.     

Could soil degradation contribute to farmland bird declines? Links between soil penetrability and the abundance of yellow wagtails Motacilla flava in arable fields

Major changes to the extent and quality of farmland habitats, brought by the intensification of agricultural practice, are thought to be the main factors driving declines in a suite of farmland bird species in Europe. Recent changes in agricultural techniques have also contributed to widespread soil degradation, arising from increased soil exposure to erosion forces, declining soil organic content and increasing soil compaction. Although soils have a fundamental influence on ecosystem properties, the implications of soil degradation for farmland biodiversity have received little attention. In this study, we measure the influence of soil conditions on the distribution of a declining insectivorous farmland bird, the yellow wagtail Motacilla flava, relative to other habitat features in arable fields. Soil penetrability was found to have a significant influence on the abundance of territorial yellow wagtails at the field scale, together with crop type. Other measured habitat features had little effect on territory abundance, including soil organic content, crop height (within preferred crop types), field boundary habitats and availability of bare ground. Monitoring of invertebrate abundance across 20 cereal fields revealed a significant influence of both soil penetrability and soil organic content on aerial invertebrate capture rates. This relationship was strongest during the latter part of the breeding season, implying that settling yellow wagtails could use soil penetrability as a predictive indicator of prey abundance during the chick-rearing period. The strong relationship between yellow wagtails and soil penetrability suggests a potential causative link between soil degradation and population decline. The role of soils in determining abundance patterns and population declines of other farmland species may have been overlooked in previous studies.     

Changes in status of the frog (Rana temporaria) and the toad (Bufo bufo) on part of the East Anglian Fenland in Britain

An attempt has been made to determine fluctuations in status of the frog (Rana temporaria) and the toad (Bufo bufo) on parts of the Fens (10 km squares TL38, 39, 48 and 49). Information from Fenland workers indicated that both species were common from at least as far back as 1900 up until the 1930s. Severe declines occured in the 1940s, 1950s and 1960s, and by the 1970s both species were very rare. Improved drainage and the marked change from pasture to arable, with associated loss of suitable wet and damp habitat, are believed to have been responsible for the early decreases. Again, loss of habitat was likely to be the main factor causing the later declines, but pesticides probably also contributed. At present, about half of the dykes containing water at a depth which frogs in other areas normally select for spawning dry out before tadpole metamorphosis would be completed.