In a population of the checkerspot butterfly, Euphydryas chalcedona , the detached wings of 309 individuals that had been attacked and eaten by birds were collected during a single flight season. During this time period a representative sample of 296 live butterflies in this population was photographed. Comparison of sex ratio and coloration of those butterflies that had been attacked with those that had not showed, first, that birds attacked slightly more females than males; and second, that among males, which are extremely variable in the amount of red on the forewing, birds attacked the less red individuals.