Marc Van De Walle

Sex-Biased Mortality of Common Terns in Wind Farm Collisions

Abstract We studied sex differences in collision mortality in adult Common Terns (Sterna hirundo) at a wind farm in the direct vicinity of a breeding site in Zeebrugge, Belgium in 2005–2007. In total, 64 fatalities were collected and sexed, of which 64% were males. Uneven sex ratio among these birds was most pronounced during the period of incubation and early chick feeding (15 May–15 June), when 78% of the 28 mortalities were male. During prelaying and feeding of young, the sex ratio of mortalities did not differ from equality. We argue that sex-biased collision mortality in Common Terns does not result from morphological differences between the sexes, but rather reflects differences in foraging frequency between males and females during egg-laying and incubation.

Seabird avoidance and attraction at an offshore wind farm in the Belgian part of the North Sea

Through before–after control-impact designed ship-based seabird surveys, seabird displacement occurring after the installation of an offshore wind farm at the Belgian Bligh Bank in 2010 was studied. Results demonstrate that northern gannet (Morus bassanus), common guillemot (Uria aalge) and razorbill (Alca torda) avoided the wind farm area, and decreased in abundance with 85, 71 and 64%, respectively. Lesser black-backed gull (Larus fuscus) and herring gull (Larus argentatus) were attracted to the wind farm, and their numbers increased by a factor 5.3 and 9.5. Other gull species too were found to frequent the turbine-built area, most notably common gull (Larus canus), black-legged kittiwake (Rissa tridactyla) and great black-backed gull (Larus marinus). The ecological incentives behind the observed attraction effects are still poorly understood, but on top of the increase in roosting possibilities it is plausible that offshore wind farms offer enhanced feeding opportunities. Importantly, attraction of seabirds to offshore wind farms implies an increased collision risk.

GPS tracking data of Lesser Black-backed Gulls and Herring Gulls breeding at the southern North Sea coast.

Abstract In this data paper, Bird tracking - GPS tracking of Lesser Black-backed Gulls and Herring Gulls breeding at the southern North Sea coast is described, a species occurrence dataset published by the Research Institute for Nature and Forest (INBO). The dataset (version 5.5) contains close to 2.5 million occurrences, recorded by 101 GPS trackers mounted on 75 Lesser Black-backed Gulls and 26 Herring Gulls breeding at the Belgian and Dutch coast. The trackers were developed by the University of Amsterdam Bird Tracking System (UvA-BiTS, http://www.uva-bits.nl). These automatically record and transmit bird movements, which allows us and others to study their habitat use and migration behaviour in great detail. Our bird tracking network is operational since 2013. It is funded for LifeWatch by the Hercules Foundation and maintained in collaboration with UvA-BiTS and the Flanders Marine Institute (VLIZ). The recorded data are periodically released in bulk as open data (http://dataset.inbo.be/bird-tracking-gull-occurrences), and are also accessible through CartoDB and the Global Biodiversity Information Facility (GBIF).

Long-term monitoring study of beached seabirds shows that chronic oil pollution in the southern North Sea has almost halted

Trends in oil rates of beached seabirds reflect temporal and spatial patterns in chronic oil pollution at sea. We analysed a long-term dataset of systematic beached bird surveys along the Belgian North Sea coast during 1962-2015, where extreme high oil contamination rates and consequently high mortality rates of seabirds during the 1960s used to coincide with intensive ship traffic. In the 1960s, >90% of all swimming seabirds that washed ashore were contaminated with oil and estimated oil-induced mortality of seabirds was probably several times higher than natural mortality. More than 50years later oil rates of seabirds have dropped to historically low levels while shipping is still very intense, indicating that chronic oil pollution has significantly declined. The declining trend is discussed in the light of a series of legislative measures that were enacted in the North Sea region to reduce oil pollution.