Dispersie na het broedseizoen, trek en overwintering van Grote Sterns Thalasseus sandvicensis uit de Voordelta = Post-breeding dispersal, migration and wintering of Sandwich Terns Thalasseus sandvicensis from the southwestern part of the Netherlands
Fijn, R.C.; Wolf, P.; Courtens, W.; Poot, M.J.M.; Stienen, E.W.M. (2011). Dispersie na het broedseizoen, trek en overwintering van Grote Sterns Thalasseus sandvicensis uit de Voordelta = Post-breeding dispersal, migration and wintering of Sandwich Terns Thalasseus sandvicensis from the southwestern part of the Netherlands. Sula 24(3): 121-135
In: Sula: tijdschrift van de Nederlandse Zeevogelgroep. Nederlandse Zeevogelgroep: Scheveningen; Oudeschild, Texel; Zeist. ISSN 0926-132X
The Sandwich Tern Sterna sandvicensis is a Dutch Red List species with a population of 19,000 pairs in the Dutch coastal zone. It winters off the coasts of Africa and a small populations migrates into the Mediterranean or stays even more north.. In the Netherlands, breeding takes places in a small number of colonies in the Delta area and the Waddensea. In this study, Sandwich Terns from the Delta colony on the Scheelhoek (Natura 2000 SPA ‘Haringvliet’) were investigated which forage during the breeding season in Natura 2000 SPA ‘Voordelta’. In total 30 adult Sandwich Terns were equipped with radio transmitters, a colourring and a plumage colour (picrinic acid or silver nitrate solution). Thanks to these markings birds could be followed in the colonies, from airplanes and from the coast. Several birds used the sand banks off the coast of their breeding colonies to rest after the breeding season. After a short while they dispersed in western and northern direction with sightings in the northern part of the Netherlands (outside and within other colonies). These were always failed breeders, possibly scouting other colonies for future breeding places. Some of these birds even left the Dutch coasts and appeared in Scotland and Denmark. Adults with young probably dispersed into the North Sea after a short stay around the sand banks off the coast near the colonies. They probably head to more nutrient rich areas in the North Sea and adjacent areas where the young birds can practice their fishing techniques before they move south. The adults can build-up here good fat reserves before the start of migration. In September, most of the marked Sandwich Terns were south of their breeding places and during their southward migration birds were seen along the coast of France and on Lanzarote (Canary Islands). Our results showed that using markers on birds could yield good data with a resighting percentage of 20% within only one year. Furthermore, the use of plumage colouring proved to be a good method for obtaining information of individual birds as these colourings attract the attention of observers and are ‘readable’ over large distances.
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