De Sperwer Accipiter nisus als broedvogel in de provincie Groningen in 2018

The number of Sparrowhawk nests found in the province of Groningen have been low in 2017 and again in 2018. A total of 43 territories were located in 2018, but – remarkably – 26 territories that were still occupied in 2016 and 2017, were found empty in 2018. The decline is also visible in two well covered municipalities (12-17 territories in 2012-16, 10 in 2017-18). The decline is partly due to urbanization with its concomitant habitat destruction, but also because of increased predation by martens Martes foina and M. martes and Goshawks Accipiter gentilis. Twenty-three out of 43 nests were situated in deciduous trees, a nest site choice of common occurrence in the province of Groningen (but conifer trees are chosen when present). Habitat choice is equally diverse, including tiny woodlots, tree rows, parks, gardens and cemeteries. At least 25 out of 43 pairs succeeded in raising one or more fledglings. Twelve out of 18 failures occurred during the egg stage, the remaining during the chick stage (and three nests that were checked twice during the chick stage showed fewer chicks the second visit, indicating partial predation). Moreover, in 81% of 16 nests chicks were infested with louseflies. The age composition of breeding pairs was checked on the basis of moulted feathers (in 2012-18): 20 out of 129 females were in their first year (16%), compared to 11 out of 37 males (30%). In 53 instances females could be individually identified (based on moulted feathers) from one year to the next: in 34 cases the female was the same, in 19 cases another female had taken over.