Wel of geen vervolglegsel van Boomvalken Falco subbuteo

Hobbies breeding in the woods near Baarn have been tracked since 2001. Between 2001 and 2014, 8 nests have been found, with distances between successive nests of 195-793 m (Fig. 1). Onset of laying varied between 1 and 10 June (average 7 June, sd=2.8, n=7). In 2013, the first Hobbies – presumably a pair - were recorded on 21 April (observations started 17 April). On 24 May, a Hobby was registered as ‘breeding’ on an old crow’s nest, and again on the same nest on 2 June. During the next visit on 16 June this nest was not occupied anymore, and only from early July onwards were Hobbies again frequently recorded in the vicinity. Not until 29 July was the nest found, when it already contained two chicks of 23 and 24 days old (onset of laying back-calculated from wing-length = age at 6 June). In hindsight, it is not likely that the observations of a ‘breeding’ Hobby on 24 May and 2 June really constituted breeding; in fact, the data seem to suggest that the bird may have tested the nest as a breeding place before switching, between 2 and 16 June, to another nest where laying commenced. Finding nests has become extremely difficult, not least because the adults behave secretively (watching them through binoculars or telescope immediately results in flight behaviour) and nest in high douglas firs (where nests are difficult to locate). This particular nest, for example, took 46 hours to find.