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.

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.

Blue, a 21-year-old harbor seal, is believed to have contracted the virus through contact with a wild bird, zoo officials said.