- The coastal and offshore waters of the UK are of global importance for several species of seabirds. The United Nations Law of the Seas and the establishment of Exclusive Economic Zones gives coastal states extensive rights but also obligations over marine areas, including the assessment of potential effects of activities on the marine environment. The Crown Estate, as landowner of the seabed out to the 12 nautical mile territorial limit plays an important role in the development of the offshore wind industry by leasing areas of seabed for the placing of turbines. The planned erection of large numbers of offshore wind turbines has underlined our lack of knowledge relating to the distribution, abundance and habitat requirements (foraging ecology) of marine birds.
- As part of the Environmental Impact Assessments for offshore wind farms, the need for detailed knowledge on spatial and temporal patterns in seabird distribution has been identified. Dedicated censuses to sample the numbers and distribution of seabirds are a basic requirement for developers, to describe bird densities within, and in the immediate vicinity of, the construction area. Studies performed need to be related to some greater area studies, in order to assess the relative and the actual importance of the construction area for the species involved.
- This document evaluates existing census techniques and determine the best currently available methods for defining bird distribution and abundance at sea. The underlying question is twofold: (1) what are the research objectives and what data are required for EIAs for offshore wind farms, and (2) how good are existing census techniques at fulfilling the objectives?
- In order to assess the potential impact of the construction of an offshore wind farm and to understand how such a construction is likely to affect the birds associated with a site, dedicated research is required. The coupling of bird census data with geographical, hydrographical, and biological measurements is essential to begin to understand how an offshore construction such as a wind farm is likely to affect an area and how the seabirds associated with a site are most likely to respond. Natural variability issues are addressed and existing census techniques have been evaluated for their potential to provide data that can be used to describe habitat characteristics and area usage by seabirds.
- The two observation tools discussed in this study, aerial and ship-based surveys, potentially provide similar data for as far as basic seabird counts are concerned (accurate numbers, accurate maps). Census techniques are similar (distance techniques using parallel bands of known width), but the level of detail for individual species is considerably less during aerial surveys. Aerial surveys are quick, so enabling coverage of larger areas per unit time, and relatively cheap, whereas ship-surveys are more time-consuming.
- Data obtained during aerial surveys may be combined with environmental parameters in a correlative approach, whereas the advantage of a ship is that such parameters can often be collected simultaneously. The slower approach with vessels allows detailed observations on seabird behaviour (habitat utilisation, feeding conditions) and diurnal/tidal fluctuations in seabird abundance and distribution.
- The acquisition of information about migration routes, direction or height of flight, detailed spatial and temporal distribution require intensive radar and direct observation in the vicinity of a proposed wind farm development to determine bird use of the area and to predict collision impact probabilities under a range of differing temporal (day/night) and weather conditions. Similarly, assessment of actual collision risk and collisions after construction necessitates static measuring devices (such as infra-red movement triggered video surveillance and vibration detection equipment currently under development). However, these tools are not addressed further in this report.