While it's tragic and alarming to see a massive die-off, it's not uncommon for birds that travel in such large populations.

In March 2022, the zoo closed the aviary for a few months due to an avian flu outbreak, at that time on the recommendation of the USDA state veterinarian after an outbreak of HPAI on an egg farm in Jefferson County.

Hundreds of red-breasted mergansers have been found either dead or sick over the past few days along Lake Michigan in Chicago and into the northern suburbs.