Finnish Museum of Natural History

Pallid Harriers

Potku the Pallied Harrier The female pallid harriers Potku and Letto

The first ever satellite transmitter on a pallid harrier (Circus macrourus) in Finland was fitted in June 2015 on a female breeding Utajärvi, Northern Ostrobothnia. The tagged bird was named Potku (a kick) after the remote village nearby its nest. Potku spent the first two winters in southern Mauretania in West Africa. She flew there and back through an  almost identical route across Poland, Germany, France, Spain and Morocco. In the summer of 2016 she tried to breed in northern Finnish Lapland and for the next summer she vanished somewhere southeast of Arkhangelsk in northwestern Russia.

The second Finnish pallid harrier fitted with a GPS-GSM transmitter was a female breeding in Lumijoki, Norther Ostrobothnia. She was captured and tagged in July 2017. This bird got her name, Letto, from the territory she has held for at least four consecutive seasons. She was first ringed there as a breeding female in summer 2014. In 2017 Letto was able to raise four fledglings – and once they could manage on their own she flew to Lapland! The tracking of the autumn migration ended too soon as Letto died in Poland already in September. She was probably predated.

By satellite monitoring we hope to shed light on the females’ use of their breeding territories as well as, especially, their migration behaviour and overwintering areas. In recent years a growing number of pallid harriers have been observed in France and Spain between September and April. This seems to points towards a new western migration route instead of the well-known route through the Middle East. Potku has already proven this speculation to be correct for her part.

Potkus’s transmitter was fitted by Ari-Pekka Auvinen and Julien Terraube, the latter of whom has studied pallid harriers in Kazakhstan. Letto’s was tagged by Auvinen and Olli-Pekka Karlin. The transmitter is powered by a solar panel and weighs 17 grams. Potku’s transmitter was supplied by Beatriz Arroyo’s research group from the The Institute of Research in Game Resources, Madrid. The fitting of Letto’s transmitter was made possible by the donation from Finnish birdwatchers.

Unlike in Kazakhstan, at least some of the pallid harriers breeding in Finland return to the same site to breed. This seems to Letto’s strategy. Potku, on the other hand, appears to just as nomadic as the pallid harriers in Kazakhstan.

Join us to follow Potku’s and Letto’s journeys and gain an insight into the behaviour of this fascinating species!

Letto's nestlings  Letto the Pallid Harrier

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Text: Ari-Pekka Auvinen, photos: Ari-Pekka Auvinen, Web management: Markus Piha