Human activity the most common cause of death for white-tailed eagles
According to a new Finnish study, lead poisoning is white-tailed eagles' most common cause of mortality. White-tailed eagles are poisoned when they ingest lead shot or fragments of lead ammunition remaining in their prey or when scavenging. Significant mortality was also caused by collision with electric power lines, cars, trains and wind turbines. During the 2000 - 2014 project, the Finnish Food Safety Authority Evira, the Finnish Museum of Natural History and WWF Finland's White-tailed Eagle Working Group collaborated in examining the causes of death of a total of 123 white-tailed eagles. Avian influenza findings and the related mortality date to a period after the material for this study was collected.
"Human-related factors accounted for up to 60 % of the causes of death. The most common of these was lead poisoning, in slightly 30 % of the cases, followed by various human-related accidents, the culprit in almost one fourth of the dead white-tailed eagles we examined", says Marja Isomursu, Senior Researcher, Ph.D. of Evira.
Lead poisoning was more common in Åland than in mainland Finland. In Åland, lead ammunition can still be used in all hunting, but on the mainland, lead shot has been prohibited in waterfowl hunting since 1996. Lead poisoning was clearly more common during the cold season, when white-tailed eagles often resort to scavenging.
Lead causes paralysis, anaemia, and typically slow emaciation. Lead is harmful to humans, too, particularly children and fetal development, as it for instance affects the central nervous system.
Natural causes of death (40 % of cases) included injuries in sexually mature birds due to territorial fights, various illnesses or starvation. Illegal shooting accounted for about 5 % of the cases studied.
White-tailed eagles' organs were also analysed for mercury. Mercury concentrations were highest in the oldest age group of mature eagles. However, no actual mercury poisoning was detected, and the levels found were no longer as high as they were in the 1960s.
The research results are published in a scientific article:
Isomursu, M., Koivusaari, J., Stjernberg, T., Hirvelä-Koski, V, Venäläinen, E.-R.
Lead poisoning and other human-related factors cause signiﬁcant mortality in white-tailed eagles. Ambio 2018.
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For further information, please contact:
Marja Isomursu, Ph.D., Senior Researcher, white-tailed eagles' causes of death, Evira, tel. +358 40 512 1248
Eija-Riitta Venäläinen, Ph.D., Head of Section, chemical analyses, Evira, tel. +358 50 434 8378
Torsten Stjernberg, Honorary Chairman of WWF Finland's White-tailed Eagle Working Group, Docent, ecology of white-tailed eagles, tel. +358 40 770 5979