Songbird migration offshore

Every year, songbirds migrate between their breeding grounds in northern Europe and their wintering grounds in southern Europe and Africa. During their migration, they also cross marine areas such as the North Sea. As the average flight altitude over the sea is significantly lower than over land, offshore wind turbines pose a potential collision risk - especially when visibility is limited. However, it is still largely unknown how many songbirds, which species and which populations actually fly over the sea. This study therefore centres on researching the small-scale flight paths and movement patterns of songbirds during migration. The focus is on understanding the preferences for flight over the sea and the associated environmental conditions. The aim is to clarify the proportion of birds that cross the North Sea as opposed to those that follow the coastline.

For this purpose, wild songbirds are fitted with small and very light transmitters that are attached like a rucksack and fall off again after a few weeks. These transmitters emit a specific radio signal, which can be received by specially erected antennas on the North Sea coast (Motus Wildlife Tracking System). This allows the flight paths of individual birds to be tracked relatively accurately both in terms of time and space. GPS technology, as we know it from navigation devices or mobile phones, is still far too heavy for small songbirds. The flight paths can be used to estimate what proportion of the population flies over the sea and could therefore be in conflict with offshore wind power. The environmental conditions (e.g. wind strength and direction, precipitation, changes in air pressure) that motivate birds to fly over the sea can also be analysed.

A second part of this cooperation project - in which large birds ranging from geese to seabirds and limicoles are being studied - is based at Kiel University's West Coast Research and Technology Centre (FTZ) and is being carried out by Prof. Stefan Garthe's working group.

Ultimately, these findings can contribute to the development of effective avoidance and species mitigation measures to minimise the impact of the expansion of renewable energies on birds.

This project builds on the BIRDMOVE (2016-2019) and TRACKBIRD (2019-2023) projects, which were completed by Dr Ommo Hüppop's Institute for Bird Research ‘Vogelwarte Helgoland’ and also by the West Coast Research and Technology Centre.