I live In the northwest so all we get are 2-3ft harmless garter snakes. Usually I'm more concerned for the snakes than the birds :/ I'd imagine a rattler wouldn't be able you do much harm to a adult bird unless it gets bare skin(leg, face or maybe a wing.)we have huge 1ft long wild rats who are always causing issues though whith disease risk and egg snatching and eating feed right in whith our chickens! We're hoping the rainy season drowns them all in their burrows....