Eerste broedsel in een boom van Slechtvalken Falco peregrinus in Nederland in het post-DDT tijdperk

After an absence of at least a decade. Peregrines started breeding again in The Netherlands in 1990. The population slowly increased from I to 10 pairs between 1990 and 2001; the present population (in 2011) is estimated at 100-125 pairs. At first, the birds nested exclusively on tall industrial buildings, then increasingly started to use crow’s nests in electricity pylons. The first natural breeding site, on the ground in a nature reserve in the western Netherlands, was recorded in 2006. In 2011, a Peregrine was found nesting on an old crow’s nest (19.5 m) in a tall willow Salix alba in the Biesbosch in the western Netherlands. This is the first tree-nesting Peregrine since 1980. The nest site was situated in a woodlot of some 0.4 ha, bordered by a poplar plantation (6 ha), a marshland and a river. The undergrowth consisted of a dense vegetation of Urtica dioica and Impatiens glandulifera. In mid-May, the nest was located by following alarm-calling adults; it contained two chicks. One of the chicks, a male of 23-24 days old, was found injured underneath the nest on 23 May. The next day, 25 May, the nest was climbed and the sole surviving chick, a female, was ringed and measured. This bird had fledged by 11 June, when some 41 days old. However, on 15 June this bird was found underneath the nest, and its emaciated condition suggested that it had not been fed in the past days. It was taken into custody, rehabilitated and released again near the nesting site on 24 June (when the parents were apparently absent). The next visit, on 27 June, showed that the chick was in good health and in company of the parents; the last observation, on 6 July, was of the juvenile flying around with a prey. Interestingly, both parents had been ringed as a chick in The Netherlands, showing that Peregrines raised on buildings or electricity pylons may nevertheless choose a tree as nesting site in later life.