Beached birds on the Flemish beaches

The history of collecting beached birds along the Flemish coast goes back to 1962. The study aims to determine the oil-rate (the proportion of oiled birds) of the beach washed birds, which is a good tool to determine trends in the chronic pollution of our coastal waters with oil. Since 1992, the Research Institute for Nature and Forest (INBO) is responsible for the Beached Bird Surveys (BBS) and organises systematic counts once a month during October - March.The numbers of beached birds fluctuated a lot over the previous decades, depending on the number of birds wintering along our coast, oil spills and weather conditions. During the winter 2006/2007, 447 beached birds were counted along the Flemish coast, being 0.99 birds km-1, close to the average number of 1.06 birds km-1 since the winter 1991/1992 (numbers of beached birds due to the Tricolor oil spill during the winter 2002/2003 are ignored in this analysis). The highest densities were encountered during February, a general tendency. Auks and gulls were the most numerous last winter, and that was always the case since the winter 1991/1992. A of Uria aalge and Razorbills) last winter will be remembered as the winter with the highest proportion of auks since the winter 1992.Guillemots and Razorbills are especially vulnerable for oil pollution because they spend most of their life swimming at beach were auks. During the first half of the winter, the oil-rate was relatively low, but the second half was characterised by a relatively high score. Recently, OSPAR (the commission for the Protection of Marine Environment of the North-East Atlantic) has recognised the oil-rate among Guillemots as EcoQ, an indicator to evaluate trends in chronic oil pollution of the marine environment. The EcoQ-objective is to force back the oil rate of Guillemots to 10% or less. When examining the changes in the oil-rate of Guillemots that washed ashore our beaches since 1962, three periods are noticeable. Between 1962 and 1990, the oil rate of beached Guillemots was very high (> 95% of all beached Guillemots were fouled). Since 1990, there was a remarkable decline with an average oil-rate of about 60%. Since 2004 the decline continued with an all time lowest score of an oil-rate of ‘only’ 17% last winter. On the other hand, there is no decline in the density of Guillemots found death along the Flemish coast, so possibly a problem in food viability is responsible for the death of many auks since 1990. Diet studies on collected auks will hopefully tell us something why auks wash ashore without any visible reason

Sex-biased mortality of common terns in wind farm collisions

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 28mortalities 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