Corncrake national surveys - territory centres
At the beginning on the 20th century, corncrakes still bred all over the UK, but by the early 1990 they were restricted to a few Scottish islands. Through conservation effort from the Royal Society for the Protection of Birds (RSPB) and Scottish Natural Heritage (SNH), the decline was reversed. This dataset contains corncrake records from all annual surveys of corncrake since 1993, monitoring the increase in corncrake numbers since then. These surveys have been funded mainly by SNH and RSPB, but also by other partners in SCARABBS (Statutory Conservation Agencies and RSPB Breeding Birds Scheme). For each year, a record in the dataset specifies the centre of the territory of one male corncrake. Territory centres are calculated from locations of singing males, recorded on multiple visits to each area covered (calls heard on separate occasions less than 200m apart are assumed to be the same bird). Since territory centres are calculated mean locations of male corncrakes, they are provided at 100m resolution, irrespective of the precision of the observations they are based upon.
All observations of singing males are provided in the dataset Annual corncrake surveys in Britain (raw data, multiple observations of each singing male). This dataset also contains the 1988 national survey, for which territory centres were not calculated.
Two types of survey are undertaken. In National surveys the whole corncrake population of Britain and the Isle of Man is surveyed. In Core Area surveys, counts are undertaken on the Hebridean islands and Orkney. These islands represent the core range of the corncrake in Britain and hold more than 90% of the breeding population. Please see the survey metadata for more details.
To estimate the population size of the corncrake in the UK, and to monitor change in numbers and results of conservation effort since the low point of the early 1990s.
RSPB fieldworkers follow the standard methodology and collect the majority of the dataset. Some records do not have a date; in this case the whole survey period (between 1st April and 31st August) is quoted. For records without a clear location at 100m precision, the 1km square is given. These data have been mapped and checked for sensitivities and typographical/geographical errors
Surveys are conducted at night. Two visits are made between 20th May and 10th July between 00.00 and 03.00 hours BST. Estimated locations of singing males are recorded in all areas known to have suitable habitat. All verified records of nests and chicks are included. Information about daytime singing locations and records outside the census period are included only if no night-time survey work can be undertaken, for example if the area is too remote. In order to verify records and validate the dataset, the data have been mapped and thoroughly checked. Geographical checks have included comparing the distribution with that shown in the published paper and ensuring that records with the same area name are located close to each other.
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