Prooikeuze van twee Bevelandse boomvalkpaartjes Falco subbuteo in 2003

In Beveland, a farmland region in the southwestern Netherlands, Hobbies declined to 7 pairs in 2003, after having reached peak numbers in 2000 (15 pairs). This study concentrated on prey choice, as overall declining populations of main prey species like swallows and sparrows (Hustings & Vergeer 2002) may be involved in the Hobby decline. Plucking sites of two Hobby pairs were visited regularly, and carefully searched for prey remains and pellets, the latter however not taken into account in this study. Both pairs fledged two young, the Rilland pair on 10 August (family gone three weeks later) and the Oudelande pair on 20 August (still present by 21 September). Prey remains were collected from July through September, at intervals of 3-4 days or weekly. Both pairs mostly preyed upon swifts Apus apus, hirundines Hirundo rustica and Delichon urbica, and sparrows Passer domesticus and P. montanus (Table 1). However, prey choice was highly variable and covered a mass range of 9 g (wren Troglodytes troglodytes) through 140 g (turtle dove Streptopelia turtur). This prey choice is in agreement with findings elsewhere in Europe. Although prey availability was not studied, it seemed that Hobbies were not limited by food supply. On the other hand, the availability of old crow’s Corvus corone nests seemed to have seriously declined on breeding grounds formerly occupied by Hobbies. This aspect of Hobby ecology will receive further attention in the forthcoming years.