Breeding Waders of Wet Meadows surveys in England and Wales, 1982 and 2002
Wet lowland grassland as a habitat has been disappearing quite fast over the last few decades as more and more has been drained or rendered less suitable for breeding birds. In the 1970s, an estimated 8000ha of the habitat was drained each year. The loss of wet lowland grassland and reduction in quality has particularly affected some wader species, which in the past have been more or less dependent on it. The BTO and RSPB have run two main surveys (1982 and 2002) to identify all areas of damp lowland grassland in England and Wales and to count the numbers of breeding waders using them. Five main species were counted: Lapwing <i>Vanellus vanellus</i>, Snipe <i>Gallinago gallinago</i>, Curlew <i>Numenius arquata</i>, Redshank <i>Tringa totanus</i> and Oystercatcher <i>Haematopus ostralegus</i>. Other rare breeding waders, which they came across were recorded, including Avocet <i>Recurvirostra avosetta</i>, Little Ringed Plover <i>Charadrius dubius</i> Ringed Plover <i>C. hiaticula</i>, Black-tailed Godwit <i>Limosa limosa</i>, Ruff <i>Philomachus pugnax</i> and Common Sandpiper <i>Actitis hypoleucos</i> as well as any Yellow Wagtails <i>Motacilla flava</i> However, this dataset only includes records of the five main species.
The surveys were intended to give an assessment of the remaining grasslands and their bird populations, and provide an inventory of the most important sites to aid the conservation of the species. The data included in this dataset are a summary of the number of birds in a site, which is represented as the central 1km grid square.
The problems of agricultural improvement are no less acute in Scotland, where the breeding wader populations of the straths and glens are under severe pressure. In 1982, a parallel survey of Breeding Waders of Scottish Agricultural Land was launched by Hector Galbraith and continued in 1983, looking at the same five wader species on all agricultural land (see Galbraith & Furness 1983 <i>Scottish Birds</i> 12: 148-153).
In both surveys, many of the birds found were on nature reserves, or other sites which had some form of protection from detrimental agricultural practices. Despite the protected nature of these sites, it is thought that the declines have continued and so careful management of all sites is essential to try to halt the declines. On a wider-scale and in the longer term, more carefully targeted agri-environment schemes may hold the key to reversing declines.
1982 survey: 1178 grassland sites in England and Wales were surveyed in 1982. In addition, a pilot survey in 1980 and 1981 covered 104 sites, which were not repeated during the main survey of 1982. Although the pilot survey data are not included in this dataset, a total of 1282 sites were surveyed covering approximately 240000ha. The area could be measured for 944 sites, and ranged from 2 ha to 1097ha with a median of 71ha (upper and lower quartiles 146ha and 30ha). Of the five key wader species, 11995 pairs were reported (6721 Lapwing, 1979 drumming Snipe, 540 Curlew, 2218 Redshank and 537 Oystercatcher). The total number of pairs exceeded 1000 in three counties: Norfolk (1983 pairs on 149 sites), Cambridgeshire (1422 pairs on 60 sites) and Kent (1262 pairs on 50 sites). It was particularly noted that 48% of the Snipe and 36% of the Redshank were found on just five sites - the Ouse Washes, Nene Washes, North Kent marshes, Derwent Ings and Somerset Levels. Even in 1982, both species were unusual breeding birds over most of the lowlands.
There was more than 30% artificial habitat on 97 sites (7.6% of the grassland sites surveyed). Artificial sites included 53 gravel pits, six sewage works, eight reservoirs and 30 other unclassified industrial sites. In total, these sites held 840 pairs of waders, and although a small fraction of the overall total (7.0%) the sites were very important in some counties, especially some inland ones.
Both surveys aimed to cover all sites, which met the specified criteria of being "wet lowland grassland" in England and Wales. All records in this dataset are collated as sites and displayed as summary central site points at 1-km resolution.
The aim of the surveys was to provide information on the species current status. The survey was also used to compare the population with previous equivalent surveys and determine population trends for waders breeding on wet lowland grassland in England and Wales.
These data have been gathered by trained field-workers and the data are of a high quality. They have also been mapped and checked for sensitivities and typographical/geographical errors.
The surveys were designed to cover all wet lowland grassland sites. This site type was defined broadly as any area of grassland subject to freshwater flooding or waterlogging. Floodplain grasslands, coastal grazing marshes and washlands are included, as well as isolated pockets of poorly drained grassland. The survey was aimed primarily at lowland grasslands and coverage was arbitrarily restricted to land below 183m (600ft) in altitude, and therefore, the uplands and their fringes were specifically excluded. Similarly, no attempt was made to survey any areas subject to regular tidal flooding. Guidelines were used to define the areas to be surveyed. Sites were selected initially by reference to the BTO Register of Ornithological Sites, water authority reports of land drainage needs, and county bird reports. BTO regional representatives, RSPB regional officers, National Agency and County Wildlife Trust officers, and county bird recorders were then consulted to produce a final list of areas that were thought to be worthy of survey in each county. All areas selected were divided into sites, and each site consisted of a geographically-defined area, which could be covered easily in one visit. A final comprehensive list of approximately 1,200 sites was produced for England and Wales. This list was thought to include all the major lowland breeding wader sites within the survey definition. In some counties, it was possible to include habitats such as gravel pits and sewage works, which were known to hold breeding waders, even though they could not strictly be defined as damp (or wet) grasslands.
Most of the particular sites surveyed in 2002 were those surveyed in 1982. However, more rigorous application of the criteria for the 2002 survey meant some original sites were excluded as they failed to meet the habitat criteria of being grassland below the altitude limit. Also excluded were locations such as the gravel pits, salt marshes or arable land. A number of additional sites were identified for the 2002 survey following extensive consultation with regional staff from the Royal Society for the Protection of Birds and English Nature (now Natural England), and the regional representatives of the British Trust for Ornithology. Some of these additional sites were areas of wet grassland created since 1982 while others were simply not covered in the previous survey.
The fieldwork was mainly carried out by volunteer fieldworkers and was organised through the national network of BTO regional representatives. However, in some areas there were large numbers of sites (eg Norfolk in 1982 and the Norfolk Broads, Somerset Levels and North Kent Marshes in 2002), in which volunteer surveys were supplemented by the work of some employed surveyors. For example, in Norfolk in 1982, two full-time fieldworkers were employed under the Manpower Services Commission Community Enterprises Project.
The methods used in the field were identical in the two surveys. Observers were asked to make three visits between April and early June. They walked through each field systematically, aiming to get to within 100m of the entire survey area. They counted total number of each wader species seen or heard, and marked their locations on a 1:25000 scale map. In addition, the observers were asked to estimate the numbers of pairs they thought were present on each visit. Observers completed visits before midday and avoided adverse weather conditions of rain or moderate to high wind. To minimise disturbance, they were not encouraged specifically to look for nests or broods, but were asked to record any that were seen in the course of the survey. It was possible that some pairs would be missed on some visits. Therefore, final overall assessments of the number of pairs present on each site were made by the observers.
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