Het wedervaren van de Raaf Corvus corax als broedvogel in Drenthe
Drentse vogels , Volume 23 - Issue 1 p. 82- 86
After the (re)settlement of the Raven as a breeding in Drenthe in 2003, a single pair continued to breed up to and including 2009. It inhabited (medium-)old stands of Scots pine Pinus sylvestris, with distances between successive nests varying between 0 and 800 m (Table 1). During these seven years, it failed to raise chicks in 2005-06, but succeeded in raising lx 2,2x 3 and 2x 4 young in the remaining five years (Table 1). The nest with 2 chicks also contained an unhatched, completely white egg of small size (Fig. 1). None of the fledglings were reported in later years (although ringed), nor was there an increase in the breeding population of Drenthe. Onset of laying was back-calculated from wing length of the oldest chick, and ranged between 25 February and 5 March (the la)ing starting on 30 March was a repeat). Measurements and weights indicate that chicks were generally in good condition. Of 62 nest visits (6 times climbing the nest tree, the remaining from the ground), only a single visit showed an absence of parents at the nest. The remaining visits showed one or both parents to be present at the nest, although the proportion of single-parent presence increased in the course of the nestling and post-fledging periods (Fig. 2).This is another indication that this pair apparently is not bottlenecked by food shortage.
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