Individual consistency in the foraging behaviour of Northern Gannets: Implications for interactions with offshore renewable energy developments

With recent EU directives requiring that Europe must achieve 20% of its energy from renewable sources by 2020 the development of offshore wind, tidal and wave technologies is gaining momentum, increasing pressure on our already vulnerable marine systems and organisms. All EU countries are required to have Environmental Impact Assessment (EIA) guidelines in place for such developments and whilst tracking studies of marine predators have been recommended to aid EIAs, they are as yet not a requirement. This study tracked Northern Gannets breeding on Les Etacs, a stack immediately offshore Alderney, Channel Islands, to determine their use of both local and international waters and examine the consistency between an individual's foraging trips. The 15 Northern Gannets that made at least two foraging trips foraged in three different territorial waters and their combined home-range area overlapped with nine potential offshore marine renewable energy developments. Repeatability between the first and second foraging trips made by an individual was apparent when considering the direction travelled and the maximum distance travelled from the colony, but not when considering the percentage overlap in core foraging areas, trip duration, or the total trip distance suggesting individuals did not appear to be dependent on specific foraging areas. Our findings highlight the need to consider all important seabird colonies which forage in the range of potential offshore developments and to use tracking technology to determine which colonies may be affected by such developments and the colony's dependence on these areas. Tracking studies of birds from important seabird colonies should form an integral part of the EIA process for marine renewable developments.