Population fluctuations of Siskins Carduelis spinus, Common Crossbills Loxia curvirostra, and Citril Finches Carduelis citrinella in relationship to flowering intensity of spruce Picea abies

Abstract

Annual population abundances from 1992 to 2002 of Siskins Carduelis spinus, Common Crossbills Loxia curvirostra and Citril Finches Carduelis citrinella were studied in relation to flowering intensity of spruce Picea abies.We used point countmethod to study the changes in abundance of the three species in the Northern Black Forest (southwest Germany). Our results indicated that Siskins and Crossbills showed large fluctuations in abundance that correlated with spruce flowering intensity in the preceding year. In contrast, abundance of Citril Finches did not correlate with spruce flowering intensity. We suggest that Citril Finches, due to their high breeding site fidelity, their less expressed exploratory breeding behaviour and their preference for pine seeds, do not react to spruce seed availability by a change in abundance as documented for the other two species.