Abstract
This report summarises existing data on seabird tracking devices: classic steel rings, which mostly only get read at deployment and once the bird is found dead; colour rings, which can be read and reported more often, but which are rarely read at sea; and telemetric tracking devices such as GPS loggers, which enable following birds in great detail, also at sea. Seabirds, being long-lived, numerous and easily accessible (in breeding colonies) have long been popular for ringing studies. For most species relevant to offshore wind farm development, ringing data exist that can be used to learn more about yearly and age-related survival. However, it will be difficult, with only two data points per ring (date and place of deployment and of the bird’s death) to relate these to offshore wind farms, which do not cause many birds to die in sharply defined incidents (such as major oil spills do). Colour ringing schemes, such as already used in large gulls for many years, and in Sandwich Tern for a shorter, but growing number of years, yield more possibilities to learn more about the survival (or mortality) of within-species groups of birds. GPS loggers provide the best data of seabirds’ usage of the open sea, including offshore wind farm areas. Many birds have already been equipped with such loggers, but mostly at relatively large distances from offshore wind farms. Specific tagging programmes related to offshore wind farms are rare, the best data probably are now collected on Helgoland.
Several possible next steps forward are identified. Detailed analyses of existing colour ringing data would be a first logical step. Colour ringing and GPS-tracking of birds in colonies closest to existing and planned offshore wind farms is advisable, as this will increase the probability that the most relevant birds (those that actually make use of offshore wind farm areas) are being tagged, rather than random birds, of which many will go elsewhere. A final and, for the Netherlands new, approach would be to catch birds directly at sea for tagging, in or near wind farm areas. This would greatly increase the usefulness of tagging data and our understanding of seabird movement around and through our offshore wind farms.