Further Information on Swedish Breeding Populations
Pernis apivorus
bivråk
ArtDatabanken 2006-05-30. Faktablad: Pernis apivorus - bivråk. Förf. Martin Tjernberg 1992. Rev. Martin Tjernberg 2005.
See ArtDatabanken for the article (pdf format) in Swedish.
Main points:
In the 1980s the population was around 8,000 pairs but in 1999 it was thought to have declined to 5,000-6,000 pairs.
There are up to 10-15 pairs per 100 km2 in optimal habitat.
Incubation takes 35 days, fledging 40 days and post-fledging to independence (in September) 14 days.
The reproduction rate was 0.6 young/monitored pair in eastern Svealand from 1986-91.
The low production is attributed to a general decline in the quality of the Swedish landscape. Hunting in the Mediterranean, particularly Malta, is also mentioned as a factor.
The low reproduction rate is compensated to some extent by the long life of the adults.
In Finland there are around 4,000-5,000 pairs with breeding up to 67 degrees N.
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