Aves, p�le ornithologique de Natagora

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Aves, 39/3-4 | 2002 | 145-158

  Development of the wintering of Great Cormorant (Phalacrocorax carbo) in Walloon Region and Brussels (Southern Belgium) between 1990 and 2003.
Paquet, J.-Y. et la Centrale Ornithologique Aves

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Article summary

Great Cormorant night roost counts are conducted in Walloon Region and Brussels area (Central and Southern Belgium) since 1990, on a monthly basis during the winter period. This Greeat Cormaorant wintering population survey offers the opportunity to describe the colonisation pattern of a new wintering area, where destrcution and disturbance of cormorants are still relatively rare. While almost no wintering cormorants were present in Walloon Region during the eighties, their current density is among highest recorder for any country in Europe (25 for 100 km2 - 5,363 individuals present in January 2003). The cormorant wintering population first settled in 1991 in the lower river Meuse valley, a slow-flowing eutrophicated and canalised river. Until the 1996-1997 winter, cormorant numbers increased steadly (+60% annually on average) but only the Meuse valley was occupied. The 1996-1997 severe winter coincided with a temporary doubling of cormorant numbers and the occupation of new sites like the Sambre, the canalised Meuse river main tributary. after a rapid reduction in number for the mild 1997-1998 winter, the wintering cormorant increased continuously (+17% annually), mostly thanks to the creation of new roost sites in the upper part of the Meuse tributaries, along ponds, lakes and canals. The establishment of new small rossts in other habitats was not associated with a decrease in number in the Meuse valley. Recently new roost creation was not anymore related to a further enlargement of potential fishing areas but, probably a reduction of roost to fishing place distances. The inter-roost distances are very low (less than 12 km in average), and cormorans coming from neighbour roosts are possibly sharing the same fishing grounds. Contrary to other wintering areas, cormorant numbers are lower in November than in mid-winter. This suggests a current possible underuse of Walloon Region as staging area during post-nuptial migration.

Articles on the same species

Grand Cormoran
Phalacrocorax carbo

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