Surveys in detail
Bioacoustic recording methods have been developed and successfully trialled to measure occurrance of particular rare species in Scotland an on Thames Basin Heaths. These surveys entail placing remote recorders at specific habitat sites identified as having potential to support the species and then using the data collected to calculate number, sex and behaviour of the birds. This method reduces surveyor bias and removes the possibility of disturbance affecting the result. See articles on our news page for more detail on these studies.
Breeding bird surveys
These surveys involve an experienced ecologist visiting the site at least three times between April and June. These habitats could be features such as woodland, hedgerows, barns/buildings, ponds or grassland. A transect is walked around the site which includes all the habitats previously identified and the area which is to be developed. Bird species and their behaviour are mapped and an assessment is made of the significance of the species present and an estimate of the number of breeding territories. This information can be used to design works to avoid or reduce adverse impacts on breeding birds and to mitigate for any loss of habitat.
Winter bird surveys
Winter bird surveys are important to establish the location of food sources and determine whether they are at risk from a proposed development. As with breeding birds, the protection of these food sources and favoured habitats can be of importance on an international scale. This type of survey requires up to four surveys, one per month. Surveys are ideally carried out during the months of November, December, January and February. A transect is walked by an experienced ecologist around the potential development site and bird species and their behaviour are mapped. An assessment can then be made of the significance of the species present and an estimate of the number of wintering birds. This information can be used to design works to avoid impact on wintering birds and to mitigate for any loss of foraging habitat.
Vantage point surveys
These types of surveys record the movements of birds flying over and landing within the proposed development area. Many bird species will fly fairly regular routes or land in specific fields, for example between roosting and feeding sites or during seasonal migration. It is important to understand if a development will interrupt or displace these flight routes or cause significant injury to bird populations. Vantage point surveys will take at least 6 – 18 months to complete and require a suitably qualified and experienced ecologist. Surveys can be started at any time of the year and, prior to the start of fieldwork, a site assessment must take place to understand the number of vantage points required and to decide on the likely survey effort. As a minimum, 36 hours per season of vantage point survey will be required. Data gathered can be used to develop collision risk models for key species and inform avoidance and mitigation measures to be included in an Ecological Impact Assessment.
The Common Bird Census (CBC)
CBC is used to estimate the number and positions of territories of each bird species present in an area during the breeding season (although annotations used within the CBC can be used for winter bird surveys also). Surveyors plot all birds seen or heard on site using unique codes to note each bird species, with sex and age where possible, and also to record activity such as song or nest-building. The registrations can then be analysed to successfully establish the potential breeding status and number of territories on a surveyed site.