Climatic effects of atmospheric carbon dioxide.

in reticulocytes (Fig. 2). The correlation coefficients for GSH/PCV and reticulocyte count for each group on each sample day were not significant when compared with published critical values (13). Elevated GSH/PCV may indicate a unique biochemical response by avian red cells experiencing oxidant stress or a toxic mechanism involving reduced activity of a GSH-dependent enzyme such as glutathione peroxidase. More detailed biochemical studies are needed before these GSH data can be interpreted. Anemia was reported in earlier experimental studies of oil ingestion by birds, but it was not characterized and generally was not considered significant (5, 14). The amount of oil ingested by wild birds that become oiled is not known, and thus we cannot precisely evaluate the environmental implications of our experimental results. Subtle but significant changes in red cell life-span or function may occur at doses that do not produce overt anemia. Disturbances of red blood cell function potentially can affect many other body tissues. Pathological changes described in studies of oil ingestion by birds (4-6) may be, in some cases, secondary or tertiary responses to a primary dysfunction of the erythron. FREDERICK A. LEIGHTON Department of Pathology, New York State College of Veterinary Medicine, Cornell University, Ithaca 14853 DAVID B. PEAKALL Wildlife Toxicology Division, Canadian Wildlife Service, Ottawa, Ontario KIA OE7 Canada RONALD G. BUTLER Department of Biological Sciences, Duquesne University, Pittsburgh, Pennsylvania 15282