Insects in the White Stork Ciconia ciconia diet as indicators of its feeding conditions: the first diet study in Slovenia

Prey remains found in the pellets of the White Stork Ciconia ciconia are known not to reveal the actual prey intake by the White Storks. The exceptions are the chitinous remains of insects that are quite well preserved in the pellets, and thus potentially good indicators of the actual intake of White Storks. Since insects are selected by White Storks in proportion to their abundance in the environment, they can be used as indicators of the quality of the bird foraging habitat. A preliminary test of this was carried out at three nests in NE Slovenia differing in their breeding success in 1997. In contrast to habitat analysis around the nest the proportions of Orthoptera and Coleoptera in the pellets corresponded well to the breeding success. Orthoptera species were dominant in high success, and Coleoptera (especially Carrion beetles Silphidae) in low success nests. In this paper the value of insects in White Stork pellets as indicators of the quality of the bird foraging microhabitat patches is set out. However, the indicative power of these insects needs to be tested further.