A female poker groupie. Could also apply to other gambling games where spectators stand around the table.
I think that railbird wants to peck at your stack.
A person that watches or gambles on a game of pool without actually playing
You should see the side money games at pool expo - I saw a race to 21 racks of 10-ball for $5,000. Must've been 50 railbirds around that table getting in on the action.