biomedicalephemera:

American Crow – Corvus brachyrhynchos

Both the American crow and the common raven (Corvus corax) are widespread, highly adaptable, and have loud and distinctive calls. Their conspicuous and ubiquitous nature made them two of the most commonly identified species in cemeteries, graveyards, and other areas associated with death and despair.

Unfortunately, the specter of death seems to have caught up to the crows – since 1999, the population of crows has dropped by over 45%, thanks to West Nile Virus. Despite the adaptability of the birds, they’re very susceptible to many avian diseases. As such, they’re considered a bioindicator (or sentinel) species – when they start dying in larger numbers, it indicates the presence of WNV or another avian disease in the area, and other birds will probably start dying soon.

The living animals of the world. C. J. Cornish, 1902.