A seal at a Massachusetts zoo died this month after contracting bird flu. Blue, the Buttonwood Park Zoo’s beloved 21-year-old harbor seal, died due to complications from Highly Pathogenic Avian Influenza, or bird flu , officials at the New Bedford zoo said Wednesday.

Bird flu has killed at least four snowy owls in Massachusetts in recent weeks, adding the graceful white and black-patterned predators to its victims as it sweeps through the wild bird population.

Owl tests positive for bird flu in Wake County

A bald eagle in Massachusetts had to be euthanized after it showed signs of neurological deficits and tested positive for bird flu. In a video shared by Raptor Tales Rescue of Shrewsbury, the bird could be seen having “sudden and frequent head movements.” This was cause for concern for it having avian influenza, also known as bird flu.

Rising numbers of great-horned owls, bald eagles and red-tailed hawks have been getting sick and dying of bird flu this winter as the virus continues to mutate and circulate in North American wildlife.