Regional Decrease in the Number of White Storks (Ciconia c. ciconia) in Relation to Food Resources

Abstract

-White Stork (Ciconia c. ciconia) numbers have been decreasing in the western part of Europe for at least 100 years. We investigated the main causes of this decrease by analysis of national and international stork census data and 19th century reports. Rainfall in the wintering areas (eastern and western Africa), taken as a relative measure for the winter food supplies, was positively correlated with the annual relative changes in number of pairs with nests in Oldenburg/Lower Saxony (Federal Republic of Germany) (1928-1984) and in Alsace (France) (1948-1970). During years with a high winter rainfall, storks arrived earlier in the breeding area and more pairs produced fledged young. The food link suggested by these data is supported by statistics on plagues of locusts and armyworms in Africa. Dates of arrival at the breeding area suggest that climatic changes have been an important cause of the initial decrease of the storks wintering in western Africa. Important causes of the decrease in the past decades were a decreased supply of locusts and drought in the wintering areas and, regionally, a deterioration of the habitat in the breeding area. We consider habitat change to be the main cause of the regional decrease of the storks wintering in eastern Africa.