Dutch marsh harrier, all the way to Ghana and back

This video, from Spain, shows a female marsh harrier, a red kite and a raven quarreling about food.

Translated from the Dutch ornithologists of Werkgroep Grauwe Kiekendief:

Thursday, May 21, 2015

A newcomer to the GPS logger research is marsh harrier “Roelof”, an adult male provided last summer with a GPS logger. Roelof returned this spring to East Groningen, with a logger packed with GPS positions. He turned out to have had a highly remarkable journey! …

Roelof returned on April 15, 2015 in East Groningen, where he presented himself at the local antenna network where we can remotely read stored GPS data. …

In the autumn of 2014 Roelof flew via Spain to his first wintering area in Senegal, where he arrived on 27 September. This route falls exactly within the narrow migration flyway which is usual for marsh harriers. Christiane Trierweiler et al. described that harriers do not remain all winter in a single area, but during the winter they move to southern areas as the northern areas get dry. These are mostly trips of several hundred kilometers.

Roelof left his first wintering area on November 10 to land about 500 kilometers to the south in Guinea. To our surprise Roelof did not stay there until the end of the winter, but he left the area on January 26 to fly 1,700 kilometers along the West African south coast, eventually ending up all the way in Ghana! Ghana is really far away for a Dutch marsh harrier, outside the ‘normal’ wintering area.

On the shores of Lake Volta

In Ghana Roelof stayed around the shores of Lake Volta. This huge lake is probably a good wintering place for marsh harriers and the question is how he ever ‘found’ this place. Did he come here in his youth by chance, making the place by now a fixed point in his annual schedule? Or perhaps Roelof has eastern genes telling him that in winter this is the place to be? Monitoring young harriers will be the key to answering this kind of exciting questions.

Roelof left the Volta Lake on February 28, keeping a northwesterly course. Aided by a firm tailwind he was ‘blown’ across the Sahara until he reached the ocean coast in the Western Sahara. From there he continued his journey towards the northeast, where he made two short stops in Morocco (as befits a marsh harrier). From Morocco, he flew straight back to exactly the same reed bed in eastern Groningen …

This photo by Ben Koks shows marsh harrier Roelof, on the left, and his female partner. On Roelof’s back, one can see his GPS logger.

Vardanis, Y., Nilsson, J.-Å., Klaassen, R. H. G., Strandberg, R. & Alerstam, T. (2016). Consistency in long-distance bird migration: contrasting patterns in time and space for two raptors [marsh harrier and osprey]. Animal Behaviour 113: 177–187: here.

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