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Institut de recherche pour la conservation des zones humides méditerranéennes

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Titre :	Roosting birds on sand islands in the Schleswig-Holstein Wadden Sea in May and September 2012
Auteurs :	Norbert Kempf, Auteur ; Klaus Guenther, Auteur ; Volkmar Fritz, Auteur
Type de document :	Article
Dans :	Vogelwelt (Die) (135(4) 2015)
Article en page(s) :	167-183
Résumé :	In the context of an approval process the company RWE Dea AG (now DEA Deutsche Erdoel AG) commissioned studies on numbers of roosting birds on remote sand islands in the Schleswig-Holstein Wadden Sea. Eight aerial surveys during high tide were conducted in May and September 2012. Using a small twin-engine aircraft (operating altitude 500 ft) and normal SLR cameras, aerial photos of all bird flocks were shot. The birds were counted on a computer screen, in part by using an image recognition software (Image J). The study showed that aerial surveys are an efficient method to cover an extensive area in one high tide period and count birds at inaccessible roosts. Significant bird numbers, which were not registered to date, were discovered. Methodological problems included the detection of bird flocks with little contrast to the surrounding ground and the identification of the small bird species. Against expectation, the birds did not react to the aircraft as long as we avoided to fly over the roosts directly. Bright weather conditions for perfect photos and operating experience in aerial surveys (cooperation of pilot and photographer) emerged to be crucial for valuable results.In May we found up to 110,000 Arctic waders on bare sand islands in the Schleswig-Holstein Wadden Sea. In the southern part of the area, 60,000 birds spent high tide in places not surveyed by ornithologists so far. Half of them were Sanderlings, a figure roughly twice the number of the entire population in Schleswig-Holstein during spring migration according to current publications. In September we recorded a maximum of 487,000 birds, almost 250,000 of them on sand islands in the southern part of the Schleswig-Holstein Wadden Sea, which had never been investigated before.It is recommended to enhance the monitoring programme for migratory birds in the Schleswig-Holstein Wadden Sea by at least two aerial surveys of the remote sand islands per year. Most important period for spring migration would be 15th to 20th May, in autumn the second half of September. A camera system with higher picture resolution would facilitate the determination of the small bird species.

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