West Nile virus and wild birds

Photo courtesy of Hamilton Greenwood (cropped)

The recent reports of eagles dying of West Nile virus (WNV) in Utah highlights the ongoing mortality in birds and other species associated with this introduced disease. The situation in Utah, where 40 eagles have died since December, is unusual because it is occurring late in the year after the mosquito season. Reports indicate eagles are contracting the disease after feeding on eared-grebes that died of West Nile virus earlier in the year, when mosquitoes were active. This route of transmission is also relatively uncommon. For further information on the situation in Utah see; http://www.heraldextra.com/news/local/bald-eagles-now-dead-from-west-nile-in-utah/article_b789a0f6-772f-11e3-ac2d-0019bb2963f4.html

This was also a somewhat higher year for West Nile virus infection in birds in Saskatchewan. This past summer the CCWHC Western Northern region diagnosed WNV deaths in a Cooper’s hawk, two northern goshawks and two nestling loggerhead shrikes, as well as nine crows. Some diagnostic testing is still pending so those numbers may increase. The death of the loggerhead shrike nestlings is particularly noteworthy as the number of shrikes has declined dramatically throughout their range and in some parts of Canada they face local extinction. In Canada, eastern loggerhead shrikes are considered endangered and prairie loggerhead shrikes are threatened. The population of shrikes has been declining for the last century and the causes for the declines are multiple and varied. As their numbers dwindle, WNV is just one more threat faced by this vulnerable species.

For further information on shrikes see: http://naturecanada.ca/bird_cons_BIRD_loggerhead_shrike.asp and http://www.gov.mb.ca/conservation/wildlife/sar/fs/lhshrike.html

Loggerhead Shrike: Flikr-Seabamirum