Can't remember if it was screened. You'd think I'd remember, since I had to remove a bird's nest from the bathroom exhaust vent. A neighbor had had the same problem, and gave me enough screen mesh to enclose the exhaust vent cover.
Then again, I discovered stack vent while doing electrical work, and it wasn't a pleasant place to be...
FWIW, the house was built ~1906.
Must have been the practice in that era. My house was built 97 years ago and the stack vent cover is down at ground level by the front porch. Fortunately someone welded the cover on REEEEEEAL GOOD.
The AA baseball team in Richmond, VA is called the Flying Squirrels.
Perhaps the Winnipeg team should change its name to the Stinky Squirrels?