Bepaling van het aantal nestjongen bij Boomvalken Falco subbuteo vanaf de grond: redelijk betrouwbaar maar wel tijdrovend
De Takkeling , Volume 5 - Issue 2 p. 25- 26
It is argued that the number of nestlings on Hobby nests can be reliably counted from the ground if the nests are observed several times during the late nestling stage for 1-2 hours per visit. Nestlings in that age are relatively mobile and are being fed regularly. The nestlings should be counted from a vantage point near the nest, preferably during early morning (nestlings hungry) and well-hidden (to prevent alarm from adults, which causes nestlings to crouch). In the western part of the province of Noord-Brabant, this procedure was followed in 1995 and 1996 and resulted in 19 nests containing respectively 1x 4, 10x 3, 7x 2 and 1x 1 nestlings/nest.
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