Slaapplaatsen van Smellekens Falco columbarius in Drenthe

A complete census and questionnaire in the province of Drenthe (2680 km2) revealed the existence of only three regular roosts. Roosts were exclusively located on the largest heaths and moors in Drenthe, i.e. Fochteloerveen (1800 ha), Dwingeloosche Heide (1200 ha) and Bargerveen (1950 ha) with maxima of respectively 4, 3 and 4 individuals in any one year in the 1990s. Closer inspection at Fochteloerveen proved that the sites were used exclusively as roost; hunting was observed only once. Birds normally started to arrive 1 hour before sunset, waited for sunset in solitary tree tops and occasionally harassed other Merlins and raptors as Goshawk Accipiter gentilis, Sparrowhawk A. nisus and Hen Harrier Circus cyaneus. The actual roosting site was very difficult to detect, because Merlins left their perches only in near-complete darkness. The observations suggest that Merlins roosted solitary on the ground. Sex-specific identification was equally difficult, but 42 observations at Fochtelooerveen positively identified 7 adult males and a possible juvenile male; most other birds had similar proportions as males, presumably also representing males. At Dwingeloosche Heide, an adult male was identified and at Bargerveen two adult males (with 2 similar-sized birds). A preponderance of males was also evident from the average size of 7 pellets (length 15.9-30.3 mm, width 8.9-12.3 mm, i.e. in the smaller range of known pellet size for Merlins; cf. Marz 1987).