As I was doing some reading through the 1908 issues of The Fowlerville Review, the following blurb caught my attention:
A new fire mocking bird whistle has been placed on the boiler at the electric light plant which will wake up almost anyone in case of fire.
I got curious what a mocking bird whistle could look like so I went online and did some poking around. I found a website that was selling, or had sold, antique whistles and found one labeled just what I was looking for. Here's the picture I found: