ABNORMAL CHICKS AND PCB RESIDUE LEVELS IN EGGS OF COLONIAL BIRDS ON THE LOWER GREAT LAKES (1971-73)

Abstract

THIS paper reports the incidence of abnormal chicks found in colonies of Black-crowned Night-Herons (Nycticorax nycticorax), Herring Gulls (Larus argentatus), Ring-billed Gulls (L. delawarensis), Common Terns (Sterna kirundo), and Caspian Terns (Hydroprogne caspia) in the lower Great Lakes. The residue levels of PCB in eggs collected from seven colonies are also reported. Abnormal chicks of fish-feeding birds have, until recent years, been infrequently reported despite a number of studies of large colonies for various purposes. A search of the North American literature has produced the following instances of abnormalities recorded incidentally to other fieldwork. Of 1500 Herring Gull chicks banded in Witless Bay, Newfoundland in 1967, only one was found with an abnormality, this being a crossed bill (Threlfall 1968). In 8 years of banding more than 125,000 Sooty Tern (Sterna fuscata) chicks, Austin (1969) noted only one abnormal chick, (with extra toes at the tarsometatarsal joints) on the Dry Tortugas, Florida. During 12 years of study in Wyoming (195970), Smith and Diem (1971) handled 6147 juvenile California Gulls (Larus californicus). Three chicks with abnormalities were found, two with lateral deflections of the upper mandible, and one with a slightly crossed bill. Ryder and Chamberlain (1972) found a single abnormal chick (with polydactyly) in 359 Ring-billed Gull chicks banded on Granite Island in northern Lake Superior. Hays and Risenbrough (1972) recorded an increase in the incidence of abnormalities in Common Terns and Roseate Terns (Sterna dougallii) on Great Gull Island, Long Island Sound, New York in 1970. In a total of 40 abnormal young of 3122 handled, various bill, eye, and foot deformities were noted in unhatched chicks and in chicks up to 3 days of age, and wing and tail feather losses were recorded in 2- to 3-weekold terns. In other colonies on the eastern seaboard 29 young Common Terns that were unable to fly because of feather loss were also reported for 1970. These abnormalities were similar to those produced in poultry (Gallus domesticus) on an experimental feeding diet contaminated with chick edema factor (Flick et al. 1965). In a PCB feeding study feather loss was seen (Vos and Koeman 1970). Tumasonis et al. (1973) found a high incidence of abnormal chicks hatching from eggs laid by PCB