finding a baby bird

I remember being told as a kid
“don’t ever pick up baby birds, because the mother will then smell human on her child, and reject it”
Well, I believed that of course, but then in my teens (or so) I heard that it was a big fat white lie!
Something about birds don’t even really have a sense of smell, and parents say that, just so kids don’t muck about with baby birds!
Anyone else been told the myth about mother birds smelling humans?
Anyone have proof that it is just a fib?

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