Definition of "birder"

Many of the crofters on Fair Isle and Shetland know as much about the birds as the birders.

1980, Bill Oddie, Bill Oddie's Little Black Bird Book, page 47

It's good to be the king. Even if the kingdom is rather small. It is amazing how often really good birders are borderline megalomaniacs.

2005, Sean Dooley, The Big Twitch, Sydney: Allen and Unwin, page 37