A large, partly pedunculated mass on the scapular area of a wild-caught captive Brown-headed Cowbird (Molothrus ater) consisted of a multiloculated keratin cyst inhabited by a new species of harpirhynchid mite (Harpirhynchus quasimodo). The mass did not interfere with flight or behavior. This is the first record of such an infestation of cowbirds in Florida.