Dynamics of the status of threatened birds breeding in Finland 1935–1985

Abstract

Lists were constructed of threatened birds in Finland in 1935, 1960 and 1985, and the changes were analysed in order to discern general patterns in the dynamics of the threatened status . The number of threatened species increased from 29 in 1935 to 38 in 1985 ; 48 of the 205 species breeding regularly in Finland before 1900 were threatened in at least one of the three periods. The status changes in 1935-85 were as follows: no change, 11 spp. (23%); deteriorated, 22 spp. (46%); improved, 15 spp. (31%). There were seven endangered species in 1935 and 1985, but three of the present endangered species were out of danger 50 years ago, and collapsed unexpectedly, whereas three of the species that were endangered in 1935 are no longer endangered. Protection seems to explain many of the improvements in status, whereas many declining species have suffered from alteration of their habitat. The effect of habitat is clearest in the case of special habitats that have been destroyedin recent decades. Ofthe out-of-danger species, as many as 6% per 25 years have become threatened. The rate of change increased from 1935-60 to 1960-85 . Non-passerines were more frequently (20-29%) threatened than passerines (5-7%), partly because non-passerines are over-represented among the less abundant species that are most threatened . At present, migration strategy does not correlate with the probability of being threatened, but the proportion of short-distance migrants that are threatened has increased from 9% in 1935 to 18% in 1985. Forests, bogs and human-made habitats have consistently had fewer threatened species than aquatic habitats, shores, rocky outcrops and fells