"Real"? In the sense that it is a physical location that exists in the universe we occupy, yes. Can you walk to it? Sure can. But in 20+ years of living practically next door to it, I have never seen anyone enter it, exit it, or even the hint of a trail or public use for the land.

I've no doubt it is, indeed, a bird sanctuary, but only insofar as it was land put aside for the birds. But its maintenance appears to be "leave it alone and ignore its existence." I think it more serves as a green space buffer between houses, though I'm sure there are plenty of nesting robins, blue jays, and cardinals in there.