Jennifer Smart

Non-intertidal habitat use by shorebirds: a reflection of inadequate intertidal resources?

Abstract Many species of shorebird typically forage almost exclusively on intertidal habitats. When such strongly maritime species choose to forage on non-intertidal habitats, it may either be a response to deteriorating intertidal conditions or to the discovery of more profitable resources in non-intertidal areas. Methods which allow distinction between these two will clearly be important for identifying problems in intertidal habitats. Since January 1998, turnstone (Arenaria interpres) on the Wash estuary, eastern England have been foraging on the docksides of Port Sutton Bridge (mainly on spilt wheat and fishmeal), fields and river edges, resulting in concern that intertidal food supplies were no longer sufficient to support the population. We quantified the distribution and behaviour of turnstone within the Wash in relation to season, tidal state and weather and used a depletion model to predict the number of turnstone that could be supported by the port, under a range of resource densities and environmental conditions. Numbers of turnstone on non-intertidal habitats increased over the winter and use of the port was significantly greater around high tide and on colder days. The depletion model showed that under virtually all conditions, the port could support a much greater proportion of the turnstone population than current peak numbers. The use of non-intertidal habitats therefore suggests that the preferred intertidal food supplies are not currently capable of supporting the turnstone population throughout the winter. Habitat switches such as this can potentially be important advance warnings of ecological changes for species, which have not yet led to reductions in population size.

Managing uplands for biodiversity: Do agri‐environment schemes deliver benefits for breeding lapwing Vanellus vanellus?

Summary Within Europe, agri-environment schemes are the key delivery mechanism for biodiversity conservation outside protected areas. Schemes have a range of land management options designed to deliver outcomes for target habitats or species. Breeding waders form an important part of the biodiversity of upland grasslands, and in the UK, there are multiple land management options within agri-environment schemes designed to benefit waders. We assessed whether such options improve the suitability of breeding habitat and population dynamics for a declining wader, the lapwing Vanellus vanellus. The suitability of nesting and chick-rearing habitat was better on land with agri-environment scheme management, and breeding densities and productivity increased with habitat suitability. The lapwing populations declined during this study, and trends did not differ between agri-environment and non-agri-environment scheme land. Productivity was below that required for population stability, although there was evidence of higher productivity on agri-environment scheme land in later years. Agri-environment management consisted of multiple land management options that varied in delivery of suitable habitat, breeding densities and success. The best management options were all in England on land benefiting from specific management advice or with rough grazing and grazed pasture agri-environment scheme options. Synthesis and applications. Despite considerable investment and positive effects of agri-environment schemes on habitat quality, populations of lapwing in the UK uplands have declined because of inadequate productivity. For species with complex requirements, populations are only likely to increase when all of these requirements are provided. Appropriately targeted habitat management, delivered through agri-environment schemes, can play an important role in improving habitat quality and increasing landscape diversity. However, when populations are limited by something other than habitat quality, for example, predation, then habitat management alone is unlikely to recover populations. Increasing evidence suggests that predation impacts are also likely to be important for ground-nesting species such as lapwing. Predator management may therefore need to be integrated with habitat measures where predation is limiting breeding success and population recovery.

Continued declines of Redshank Tringa totanus breeding on saltmarsh in Great Britain: is there a solution to this conservation problem?

Capsule: Over 50% of saltmarsh breeding Common Redshank have been lost since 1985, with current conservation management having only limited success at halting these declines. Aims: To update population size and trend estimates for saltmarsh-breeding Redshank in Britain, and to determine whether conservation management implemented since 1996 has been successful in influencing grazing intensity and Redshank population trends. Methods: A repeat national survey of British saltmarsh was conducted in 2011 at sites previously visited in 1985 and 1996. Redshank breeding density and grazing pressure were recorded at all sites; the presence of conservation management was additionally recorded for English sites. Results from all three national surveys were used to update population size and trend estimates, and to investigate changes in grazing pressure and breeding density on sites with and without conservation management. Results: Of the 21 431 pairs breeding on saltmarsh in 1985, 11 946 pairs remained in 2011, with the highest proportion of this population found in East Anglia. From 1985, British breeding densities declined at a rate of 1 pair km−2 year−1, representing a loss of 52.8% of breeding pairs over 26 years, although regional trends varied across different time periods. Grazing pressures did not change markedly with conservation management. Redshank declines were less severe on conservation-managed sites in East Anglia and the South of England where grazing pressures remained low, though were more severe on conservation-managed sites in the North West where heavy grazing persisted. Conclusion: Saltmarsh-breeding Redshank declines continue and are likely to be driven by a lack of suitable nesting habitat. Conservation management schemes and site protection implemented since 1996 appear not to be delivering the grazing pressures and associated habitat conditions required by this species, particularly in the North West of England, though habitat changes may not be linked to unsuitable grazing management in all regions. An in-depth understanding of grazing practices, how conservation management guidelines could be improved, and the likely success of more long-term management solutions is needed urgently.

National-scale analyses of habitat associations of Marsh Tits Poecile palustris and Blue Tits Cyanistes caeruleus : two species with opposing population trends in Britain

Capsule Marsh Tits were strongly associated with both the amount and species diversity of woodland understorey; Blue Tits were associated with large trees and deadwood. Aims To gather quantitative information on the habitat requirements of Marsh Tits, in comparison with those of Blue Tits, across a large number of sites in England and Wales, and secondly to evaluate the range of habitat conditions likely to encourage the presence, and increase the abundance of, each species. Methods Counts of birds were made at each of 181 woods across England and Wales, and habitat data were collected from the same locations in each woodland. Marsh Tit and Blue Tit presence and abundance were related to habitat characteristics, interspecific competition and deer impact. Results Shrub cover and species diversity were important for the presence and abundance of Marsh Tits, across their geographical range in Britain. Blue Tits were associated with large trees and deadwood. Conclusion Our results support the hypothesis that changes in woodland management, leading to canopy closure and a decline in the understorey available, could have had an impact on Marsh Tits, and may have led to the observed population decline. These same changes were also consistent with population increase in Blue Tits.

Landscape effects on nest site selection and nest success of Northern Lapwing Vanellus vanellus in lowland wet grasslands

ABSTRACT Capsule: Northern Lapwing Vanellus vanellus avoid nesting close to small woodland patches but nest predation rates do not vary with distance to woodland patches, either because risky areas are avoided or perceived nest predation risk does not reflect actual risk. Aims: To explore the effects of woodland patches in wet grassland landscapes on nest distribution and success of Lapwings. Methods: We quantified the effect of woodland patches on the distribution and outcome of Lapwing nests across four wet grassland sites by mapping nest distribution and monitoring nest outcomes. Results: Lapwing nested significantly further from woods than expected by chance. Neither nest predation rates nor the probability of predation occurring at night (thus primarily mammalian predators) or day (primarily avian predators) varied in relation to distance from woodland patches. Conclusions: High levels of nest and chick predation in wet grassland landscapes limit the capacity for breeding wader populations to be self-sustaining. Consequently, identifying manageable landscape features that influence predation rates is an important focus of conservation research. Lapwing avoid breeding close to woodland but, as nest predation rates do not vary with distance from woodland patches, their removal may increase the area of suitable nesting habitat but is unlikely to substantially influence productivity.

A review of predation as a limiting factor for bird populations in mesopredator-rich landscapes: a case study of the UK: Predation on UK birds

The impact of increasing vertebrate predator numbers on bird populations is widely debated among the general public, game managers and conservationists across Europe. However, there are few systematic reviews of whether predation limits the population sizes of European bird species. Views on the impacts of predation are particularly polarised in the UK, probably because the UK has a globally exceptional culture of intensive, high‐yield gamebird management where predator removal is the norm. In addition, most apex predators have been exterminated or much depleted in numbers, contributing to a widely held perception that the UK has high numbers of mesopredators. This has resulted in many high‐quality studies of mesopredator impacts over several decades. Here we present results from a systematic review of predator trends and abundance, and assess whether predation limits the population sizes of 90 bird species in the UK. Our results confirm that the generalist predators Red Fox (Vulpes vulpes) and Crows (Corvus corone and C. cornix) occur at high densities in the UK compared with other European countries. In addition, some avian and mammalian predators have increased numerically in the UK during recent decades. Despite these high and increasing densities of predators, we found little evidence that predation limits populations of pigeons, woodpeckers and passerines, whereas evidence suggests that ground‐nesting seabirds, waders and gamebirds can be limited by predation. Using life‐history characteristics of prey species, we found that mainly long‐lived species with high adult survival and late onset of breeding were limited by predation. Single‐brooded species were also more likely to be limited by predation than multi‐brooded species. Predators that depredate prey species during all life stages (i.e. from nest to adult stages) limited prey numbers more than predators that depredated only specific life stages (e.g. solely during the nest phase). The Red Fox and non‐native mammals (e.g. the American Mink Neovison vison) were frequently identified as numerically limiting their prey species. Our review has identified predator–prey interactions that are particularly likely to result in population declines of prey species. In the short term, traditional predator‐management techniques (e.g. lethal control or fencing to reduce predation by a small number of predator species) could be used to protect these vulnerable species. However, as these techniques are costly and time‐consuming, we advocate that future research should identify land‐use practices and landscape configurations that would reduce predator numbers and predation rates.

Nest trampling and ground nesting birds: quantifying temporal and spatial overlap between cattle activity and breeding redshank

Abstract Conservation grazing for breeding birds needs to balance the positive effects on vegetation structure and negative effects of nest trampling. In the UK, populations of Common redshank Tringa totanus breeding on saltmarshes declined by >50% between 1985 and 2011. These declines have been linked to changes in grazing management. The highest breeding densities of redshank on saltmarshes are found in lightly grazed areas. Conservation initiatives have encouraged low‐intensity grazing at <1 cattle/ha, but even these levels of grazing can result in high levels of nest trampling. If livestock distribution is not spatially or temporally homogenous but concentrated where and when redshank breed, rates of nest trampling may be much higher than expected based on livestock density alone. By GPS tracking cattle on saltmarshes and monitoring trampling of dummy nests, this study quantified (i) the spatial and temporal distribution of cattle in relation to the distribution of redshank nesting habitats and (ii) trampling rates of dummy nests. The distribution of livestock was highly variable depending on both time in the season and the saltmarsh under study, with cattle using between 3% and 42% of the saltmarsh extent and spending most their time on higher elevation habitat within 500 m of the sea wall, but moving further onto the saltmarsh as the season progressed. Breeding redshank also nest on these higher elevation zones, and this breeding coincides with the early period of grazing. Probability of nest trampling was correlated to livestock density and was up to six times higher in the areas where redshank breed. This overlap in both space and time of the habitat use of cattle and redshank means that the trampling probability of a nest can be much higher than would be expected based on standard measures of cattle density. Synthesis and applications: Because saltmarsh grazing is required to maintain a favorable vegetation structure for redshank breeding, grazing management should aim to keep livestock away from redshank nesting habitat between mid‐April and mid‐July when nests are active, through delaying the onset of grazing or introducing a rotational grazing system.