Zeearend Haliaeetus albicilla contra Visarend Pandion haliaetus?

In 2012, a White-tailed Eagle bred for the first time in the Biesbosch, a large wetland in the southwestern Netherlands; a single chick was raised. On 19 August 2012, this fledgling was seen begging for food near an adult White-tailed Eagle. Based on size differences, the fledgling was considered to be a female (this bird was neither ringed nor measured whilst on the nest), the adult a male. Two Ospreys entered the scene, one of which made a long stoop towards the eagles sitting on a bank, which behaviour apparently prompted the adult male to start chasing the Osprey at full speed. Photographs of the ensuing interaction showed that the adult Osprey (in tail moult) had been carrying a small fish, which was kleptoparasitized by the White-tailed Eagle. Another case of successful kleptoparasitic behaviour between an adult male Whitetailed Eagle and and adult Osprey was observed not much later in the same wetland. This behaviour is well known from the ornithological literature. Questions are raised whether the presence of breeding White-tailed Eagles may prevent Ospreys from settling as a breeding bird, as surmised for regions elsewhere within the breeding range of the Osprey. Since decades, summering Ospreys have been frequently recorded in suitable habitats in The Netherlands, but – apart from nest-building in the Oostvaardersplassen in 2002 – no breeding attempts have been observed. Contrarily, White-tailed Eagles started breeding in The Netherlands in 2006, and in 2012 already were present with five breeding pairs, mostly in wetlands suitable for Ospreys as well (as testified by summering individuals). How the future will develop regarding colonisation and distribution of both raptors, remains to be seen.