Scientific publications

The productivity of the Sea Eagle in Finland began to deteriorate in the 1950s, reaching its lowest level during the 1970s. The breeding population diminished, from approximately 55 pairs in 1960 to ca. 40 pairs in 1970, many of them incapable to reproduce. Associated with active protective measures, breeding success improved, and the population increased to about 50 pairs in 1980, 80 pairs in 1990, 200 pairs in 2000 and 300 pairs in 2005. The number of occupied territories increased from 37 in 1980, to 75 in 1990, 167 in 2000, and 255 in 2005, including 4, 14, 21 and 34 fresh water or inland territories in northern Finland, respectively. The total annual number of nestlings in the early 1970s varied between 4 and 10. It was 17 in 1980, 62 in 1990, 172 in 2000, and 256 in 2005. Nestlings per occupied territory was <0.3 in the 1970s, slightly higher in the early 1980s, and increased during the 1980s and 1990s to about 0.94 in 2000–2004. The improvement of the breeding success started some years earlier on the Aland Islands than in other sub-regions. During the period 2000–2004 about 60% of the nesting attempts were successful compared to only about 20% (16–23%) in 1970–1974. The average brood size increased as well, e.g. on the Aland Islands from 1.21 nestlings 1976–1979 to 1.65 in 2000–2004. Considering the high productivity and low mortality among juveniles and sub-adults since the
1990s, the population should continue to increase.