Surveys of breeding birds

While there are a number of existing approaches to surveying birds in the breeding season , including territory mapping options such as the Common Bird Census (CBC) (Marchant, 1980) and citizen science approaches such as the Breeding Bird Survey (BBS) run by the British Trust for Ornithology (BTO), these methodologies were/are designed to monitor long-term trends in bird populations at a national level.  As such they are broadly unsuitable for fine-scale applications, such as ecological impact assessments, which are often undertaken in a single season.  As a result, there is an absence of a clear  methodology for undertaking ornithological surveys in the bird breeding season.  It is the purpose of the guidance provided here, to address this gap.

Note – we are trying to avoid the use of the term Breeding Bird Survey (BBS) as this has already been adopted by the BTO.

This guidance is loosely based on the CBC technique, making use of repeated visits in a single season (albeit less visits compared to CBC recommendations) and some simplified elements of territory behaviour mapping. However, where CBC asks exactly how many individuals are nesting (or holding territory) in a given area, this guidance seeks to measure in what way, if at all, a given area is important to avian diversity, what species could potentially be breeding and, therefore, what the impacts of the project or development being considered are likely to be.  When gathering survey information we must be mindful of the Precautionary Principle as defined by CIEEM:

“The evaluation of significant effects should always be based on the best available scientific evidence. If sufficient information is not available further survey or additional research may be required. In cases of reasonable doubt, where it is not possible to robustly justify a conclusion of no significant effect, a significant effect should be assumed. Where uncertainty exists, it must be acknowledged in the EcIA”.

For the purposes of surveys of breeding birds it is necessary to understand not only what bird species are potentially present within the survey area, but also the conservation value of its breeding bird assemblage, in both a local and wider context, as well as how the survey area is used by birds in the breeding season.  In some cases it might be useful to produce a constraints plan showing which areas of a site are of most importance to breeding birds.

It is intended that this guidance provides an approach that can be consistently implemented across the ecological consultancy industry, and it is therefore, applicable to the collection of data in both terrestrial and freshwater habitats. However, the guidance recognises that some deviations may be required for highly specialised applications (e.g. where likely significant effects are anticipated in respect of Special Protection Areas or Ramsar sites) and as such the guidance is designed to encompass some degree of flexibility to site and species-specific survey planning. It is therefore recommended that this guidance is treated as a base-line protocol and variations assessed and appropriate justified if they are required.

There is additionally consideration within this guidance of circumstances where certain unconventional survey methods (e.g. passive audio monitoring or nocturnal using night vision equipment) might be beneficial in the collection of supplementary data.

Guidance for surveys of breeding birds is provided in the following sections: