Kieskeurig foerageren door een Houtduif Columba palumbus

Contents of crop and stomach of a female adult Woodpigeon (441 g), freshly killed by an adult male Goshawk while foraging on beech-nuts in northern Drenthe, were examined. The stomach contained mashed maize and beech-nuts, six kernels of sweet cherry and 85 pieces of grit. Combined weight of the grit was 1.6 g, mean grit length 3.0 mm (SD=0.81), median length 2.9 mm (Figure 1). The crop contained 22 beech-nuts, 19 grains of maize, 1 snail Succinea oblonga (height 7.7 mm) and 1 piece of grit (3.3x2.0 mm). All 22 beech-nuts from the crop were full, contrasting with a sample of 122 beech-nuts from an area of 0.25 m2 at the feeding site of the same pigeon, in which 11% was empty. Furthermore, the mean weight of a single nut from the crop was 0.17 g, as compared to a mean of 0.08 g/nut from the sample at the feeding site. Apparently, while foraging the Woodpigeon had made a choice between empty and full beech-nuts, meanwhile selecting for the heavier nuts. Probably, visual clues (rather than tactile) were used in this selection procedure, as was experimentally made plausible by collecting 22 apparently heavy beech-nuts by myself (mean weight 0.2 g/nut).