Is West-Drenthe een brongebied van Raven Corvus corax voor de wijde omgeving?

Bijlsma R.G. 2013. Breeding output of a Raven Corvus corax pair in western Drenthe in 2003-2013: source of the regional colonization? Drentse Vogels 27: . After a long prelude Ravens started breeding in the northern Netherlands in 2003. Since then, a single pair in western Drenthe was closely monitored up to and including 2013. It bred successfully in 9 out of 11 years (including a repeat laying), raising a total of 31 fledglings. All chicks were ringed, but only a single recovery was obtained (ringed on 27 April 2010 and recovered recently dead on 17 October 2010 at a distance of 35 km). Since a few years, some more pairs started breeding in the northern Netherlands (at least five newcomers), but it is not known whether the productive pair in western Drenthe may have triggered this slight increase. A colour-ringing programme was started in 2013, to improve the chances of sighting an individually recognisable bird.