Bettina Mendel

Effects of ship traffic on seabirds in offshore waters: implications for marine conservation and spatial planning

Most anthropogenic influences on marine ecosystems, except for river- or terrestrial-borne pollution, involve some sort of vessel activity. Increasing anthropogenic activities mean that many countries are being forced to develop spatial planning schemes, while at the same time implementing conservation sites for sensitive species at sea. The effects of ship traffic on seabirds sensitive to human disturbance are currently too poorly understood to allow for the development of proper planning and conservation guidelines. We therefore used aerial surveys and experimental disturbance to elucidate the effects of passing ships on the distribution patterns, habitat loss, and species-specific flight reactions of birds, as well as the potential for habituation. Loons (Gavia spp.) showed clear avoidance of areas with high shipping intensity. Flush distances of four sea duck species differed significantly, with the longest distances recorded for Common Scoters (Melanitta nigra) and the shortest for Common Eiders (Somateria mollissima). Flush distance was positively related to flock size. Among all the sea duck species studied, the duration of temporary habitat loss was longest for Common Scoters. We found indications of habituation in sea ducks within areas of channeled traffic. However, it is questionable if habituation to free-ranging ships is likely to occur, because of their unpredictable nature. We therefore recommend that spatial planning should aim to channel ship traffic wherever possible to avoid further habitat fragmentation and to allow for habituation, at least in some species. Information on the effects of shipping on other seabird species and during different periods of the year is urgently needed, together with information on the effects of different types of boats, including recreational and fishing vessels.

Varying foraging patterns in response to competition? A multicolony approach in a generalist seabird

Abstract Reducing resource competition is a crucial requirement for colonial seabirds to ensure adequate self‐ and chick‐provisioning during breeding season. Spatial segregation is a common avoidance strategy among and within species from neighboring breeding colonies. We determined whether the foraging behaviors of incubating lesser black‐backed gulls (Larus fuscus) differed between six colonies varying in size and distance to mainland, and whether any differences could be related to the foraging habitats visited. Seventy‐nine incubating individuals from six study colonies along the German North Sea coast were equipped with GPS data loggers in multiple years. Dietary information was gained by sampling food pellets, and blood samples were taken for stable isotope analyses. Foraging patterns clearly differed among and within colonies. Foraging range increased with increasing colony size and decreased with increasing colony distance from the mainland, although the latter might be due to the inclusion of the only offshore colony. Gulls from larger colonies with consequently greater density‐dependent competition were more likely to forage at land instead of at sea. The diets of the gulls from the colonies furthest from each other differed, while the diets from the other colonies overlapped with each other. The spatial segregation and dietary similarities suggest that lesser black‐backed gulls foraged at different sites and utilized two main habitat types, although these were similar across foraging areas for all colonies except the single offshore island. The avoidance of intraspecific competition results in colony‐specific foraging patterns, potentially causing more intensive utilization of terrestrial foraging sites, which may offer more predictable and easily available foraging compared with the marine environment.

Effects of the alpha ventus offshore test site on distribution patterns, behaviour and flight heights of seabirds

The North Sea and its adjacent waters are an area of world-wide importance for seabirds. With regard to the establishment of offshore windfarms, it becomes necessary to investigate the possible effects of these installations. In this project, distribution patterns of seabirds were determined and detailed observations were made on the behaviour and flight heights of individual birds in and around the alpha ventus windfarm area. Data was used from the combined database on seabird abundance and distribution in order to make predictions and draw conclusions about selected seabird species in relation to alpha ventus. A recently developed digital method for aerial surveys was also tested in the course of this project.

Possible Conflicts between Offshore Wind Farms and Seabirds in the German Sectors of North Sea and Baltic Sea

In conclusion, it is obvious that depending on avoidance behaviour and collision risk as well as on the proportions of populations affected, the impact of offshore wind farms in the German sector of the North Sea on seabird populations differs considerably. The example of Red-throated Divers and Common Guillemots shows that large parts of the German Bight would be excluded from use by these species. This has to be taken into account in the process of commissioning by authorities and should lead to the application of threshold levels in order to select wind farm sites which have least impact on seabird populations. The above examples demonstrate that in the assessment of the effects of a single wind farm, the habitat loss in addition to the habitat already lost before due to other wind farms must be considered. Therefore, this underscores the need for a cumulative approach when assessing impacts on seabird populations.

Adult Gannet migrations frequently loop clockwise around Britain and Ireland

ABSTRACT The Gannet Morus bassanus is one of the seabirds considered most at risk from collision mortality at offshore wind farms in UK waters, so a better understanding of migration routes informs assessments of risk for different populations. Deployment of geolocators on breeding adults at the Bass Rock, Scotland, and Skrúður, Iceland, showed that the timing of migrations differed between populations, birds from Bass Rock passing south through UK waters mostly in October and back in February while birds from Skrúður passed south through UK waters mostly later, in November, but returned north earlier, in January. Many birds from both colonies made a clockwise loop migration around Britain and Ireland. Only a minority of birds from the Bass Rock returned northwards to the colony through the southern North Sea. A counter-intuitive consequence is that many Gannets moving northwards through waters to the west of Britain and Ireland in spring may be birds from North Sea colonies. Although Gannets normally remain over the sea, one tracked bird appears to have made a short overland passage in spring from the west of Scotland through central Scotland to the Bass Rock, whereas most returned around the north of Scotland.