WASSINK G (2003) First breeding of Eurasian Eagle Owl Bubo bubo in the Achterhoek, eastern Netherlands. LIMOSA 76 (1): 1-10.

In May 2002, a nest of Eurasian Eagle Owl was discovered in a small forest in the Achterhoek, province of Gelderland, in the eastern part of the Netherlands near the German border. The nest contained three young, of which one died soon after discovery. The nest was situated at 13 m height in a Scots Pine, but came down with two of three young. Based on the estimated age of the young, the first egg was laid around 1 April. Observations were made of the behaviour of the two young and the amount of prey they consumed. For this purpose, searches for pellets and prey remains were made weekly between 17 July and 20 October. Besides, once a week observations of the behaviour of the birds were made. By the end of July, the two young started to fly short distances and became active (i.e. called for prey) well before sunset. In late summer and autumn, start of activities shifted more towards sunset and later (Fig. 1). Analysis of prey remains and pellets revealed a clear preference for homing pigeons (57% of all prey in number, 31% in biomass; Tab. 1). Mammalian prey often included Western Hedgehog Erinaceus europeus and Rabbit Oryctolagus cuniculus, especially when considering biomass. During autumn, the amount of avian prey decreased and more mammals were found (Fig. 3). Remains of a Roe Deer Capreolus capreolus occurred once among the prey remains, suggesting that the owls also took carrion. A reconstruction indicates that a young owl consumed 378 g of prey per day between 2 July and 11 October. Prey intake increased during the season (Fig. 2) and the increase in August coincided with changes in activity (i.e. birds becoming more mobile). Together with an assumed 400 g daily prey intake by the adults, one pair of Eagle Owls and two young are estimated to consume about 1500 g of food daily. This successful expansion of Eagle Owls into the eastern part of the Netherlands follows earlier settlement in the extreme south of the country, where Eagle Owl has bred from 1997 onwards (2002: 2 pairs). In both regions, thriving populations are found across the border with Belgium (Limburg) and Germany (Achterhoek). A further expansion of the population in border regions is expected.

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