Desk study

Desk study data typically consists of species records, statutory and non-statutory designated site information and contextual information (e.g. aerial photographs and previous reporting) relevant to the site and surrounding landscape.

The gathering of desk study data can help determine if protected or notable bird species may occur within or near the site, and will in turn inform the decision whether it is valid to scope out the need for surveys as well as helping with survey design.

Designated sites

The desk study should include consideration of statutory and non-statutory designated sites.

Are there any designated sites within, adjacent to or connected to the development site (the zone of influence) that are designated for their bird assemblage or include birds in their citation?

​The distance at which designated sites would be considered will vary depending on the project and zone of influence, habitats, location and various forms of connectivity including ecological and hydrological. For example, for a project affecting coastal arable fields, it may be appropriate to consider Special Protection Areas (SPA) further afield e.g. a qualifying SPA population of brent geese may forage within farmland and amenity grassland outside an SPA.


A list of potential sources of desk study data is provided in Additional Resources. This is not an exhaustive list, but is intended to provide an overview of the most appropriate sources to consider.

​It is not considered that all data sources will need to be consulted in every case. The extent and nature of data sources requiring consideration will be dependent upon the nature, scale and location of the proposed development.

It is often the case that other ecological surveys will be being undertaken on a site e.g. bat surveys. Information on suitability of habitat and birds encountered during these surveys can be a useful source of information during the scoping stage.

One data source to highlight here is the BTO Data Reports. These reports provide scientific information to inform desk studies and aid in fieldwork decisions. Unlike some alternative data sources a BTO data report presents you with a list of all bird species present near your site in both the breeding season and winter using a GIS file of the site.

Extent of desk study

A decision on the extent of any desk study search area should be made at an early stage in the scoping process.

The desk study search should consider the likely zone of influence of a development/project. This will include the area within the proposed development site as well as an appropriate buffer. The extent of this buffer should be proportional to the sensitivity of the scheme and surrounding landscape, and the scale and nature of the proposed development. The extent of the desk study will also be dependent on the spatial scale at which the data are available.

Further guidance on appropriate zones of influence can be found within the following resources:

  • Guidelines for Preliminary Ecological Appraisal (CIEEM, 2017)
  • Guidelines for Ecological Impact Assessment in the UK and Ireland: Terrestrial, Freshwater, Coastal and Marine v1.1 (CIEEM, 2018)
  • Bat Surveys for Professional Ecologists: Good Practice Guidelines (Collins, 2016)


Desk study data should be reviewed and interpreted by ecologists who are competent ornithologists to ensure that the implications of bird species records and/or statutory or non-statutory designated sites are accurately determined. This is required owing to the varying conclusions that can be drawn from bird species records recorded at different times of the year. 

Examples of key questions that should be considered when interpreting desk data could be:

  • have any breeding Schedule 1, or otherwise notable, bird records been recorded within the zone of influence? (see Scoping for Schedule 1 surveys for further information on how to proceed where Schedule 1 species have been identified);
  • are any designated sites with qualifying bird features and/or other locations of note to birds (i.e. local wildlife sites and/or nature reserves) present within the zone of influence?;
  • are there habitats present within the proposed development site and/or the zone of influence which are known to be of value to notable bird species and/or assemblages (e.g. woodland or heathland habitats which support bird species of conservation concern)?;
  • where does the proposed development site lie geographically? Is this location known to be of importance to birds? Does this importance vary on a seasonal basis?

A further important consideration following the interpretation of the desk study data is to consider whether there are sufficient and suitable desk study data to avoid the need for survey work. For example, regular long-term WeBS data may negate the requirement for surveys for wetland sites. When making this determination it is important to consider whether the data available are of sufficient quality, sufficiently recent (see CIEEM guidance) and at the correct spatial scale. Furthermore, are the data available to the public and/or permitted to be used for commercial purposes?

Desk study data should also inform the surveys required. For example in addition to breeding and non-breeding bird surveys, species-specific survey methods may also be required.

Desk study data may also enable the determination of reporting and assessment requirements. For example, it might be determined that a housing development on previously developed land might not require any bird survey; however, this development might increase recreational pressure on a SPA site, in which case there will be a requirement for a statement to inform a HRA assessment to determine the impact of recreational pressure on bird species associated with the SPA.