The birds feed on the crabs' eggs, but the bird population has been dwindling as the eggs have become more scarce.
Environmental groups and state officials say the red knots could go extinct by 2010 if they don't get protection.
The ban is opposed by fisherman who harvest horseshoe crabs for use as bait. They say other factors may be responsible for the birds' diminishing numbers.
The Senate is set to vote on the bill on Monday.
