Migration of the Great Black-backed Gull

Since 2024 we have been tracking the movements of Great Black-backed Gulls to better understand their spatial ecology. This is important because, despite this being the largest gull species in the world, relatively little is known about their movements and behaviour throughout the year. For this project, commissioned by Ecowende CV, we are collaborating with BirdLife Norway, as many ringed birds observed in the Netherlands (where only a few pairs breed) originate from breeding colonies in Southern Norway.

To date, our team of experts has equipped 50 Great Black-backed Gulls with GPS transmitters. This allows us to track their movements throughout the year and obtain detailed information about their main foraging areas during the breeding season and to where they migrate. This is the first project of its kind and provides data with high spatial and temporal resolution, which can be used to determine how Great Black-backed Gulls interact with offshore wind farms.

This knowledge is crucial for Ecowende, which is building a new wind farm in the North Sea (Hollandse Kust West) and aims to design this and future wind farms to be as bird-friendly as possible. In 2027 and 2028, we will return to Norway to tag another 50 birds and study their movements after the construction of Hollandse Kust West.

After the breeding season in Norway, most tagged birds migrated south to warmer waters. Some individuals found a nice spot along the coast of France or Belgium, where they stayed during the winter. Other birds spent the entire winter at sea, possibly resting on offshore structures such as platforms and even wind turbines.

This latter group, in particular, is central to our follow-up research, in which we investigate the extent to which offshore wind farms influence the behaviour of Great Black-Backed Gulls. Do they avoid wind farms, or do they actually become accustomed to them and perhaps even attracted to them? And how can we help reduce the risk of collisions with the turbines' blades?

This project will help answer these important questions, thereby providing insights into the effects of offshore wind farms on seabirds. The results offer both wind farm owners and the Dutch government a scientifically substantiated basis for making informed choices regarding the development of future sustainable renewable energy projects.

The field team consisted of: (from left to right) Marin van Regteren (Ecowende), Morten Helberg (Birdlife Norway), Cas Eikenaar and Ruben Fijn (Waardenburg Ecology).