Pollutant and Shell Thickness Determinations of Peregrine Eggs from West Greenland

A preliminary survey of breeding peregrine falcons ( Falco peregrinus ) in West Greenland in 1972 indicated both a high nesting density (one pair per 100 square miles) and a high production rate (2.25 young per pair or 2.57 per pair with young). Peregrines in the eastern United States and southern Canada experienced an increasing incidence of reproductive failures throughout the 1950s and early 1960s, culminating in the disappearance of the breeding populations by 1964. Studies were therefore carried out in the Northwest Territories and Alaska in 1966 to determine the status of the northern birds. No apparent abnormalities were found, and the reproduction was considered to be normal. Thin eggshells have been a characteristic of all the declining populations. The degree of thinning is closely associated with levels of the DDT compound p,p'-DDE in the eggs . We have therefore examined the eggshells and shell fragments obtained in Greenland in 1972 for evidence of shell thinning and have measured the chlorinated hydrocarbons in two unhatched eggs. During the 1972 Greenland peregrine survey, 1 unhatched egg was collected from each of 2 eyries. In addition, shell fragments of 7 hatched eggs from 4 different females were collected. The mean thickness of these 9 eggs from 6 females was 0.298 mm ±0.018 (95 per cent C.L.: range 0.26-0.33), 14 per cent lower than the mean thickness of 42 peregrine eggs from Greenland that were collected before 1940 (thickness = 0.347 mm ±0.018 .). Shell thinning of unhatched and broken eggs obtained from Ungava in 1967 and 1970 was somewhat more severe; the mean thickness was 21 per cent less than that of 59 peregrine egg-shells collected in the eastern Arctic between 1900 and 1940. DDE concentrations, expressed on either a wet weight or a lipid weight basis are within the range of those measured in peregrine eggs from Alaska and northern Canada. Polychlorinated biphenyls (PCB) have not previously been determined in peregrine eggs from the Arctic. Levels in the Greenland eggs were comparable to those of DDE . The composition of the PCB mixture was similar to that of commercial mixtures containing 60 per cent chlorine by weight, Profiles of PCB residues in these eggs are strikingly like those of fat biopsies from peregrines in Chile, a further example of the global nature of the contamination to which this species is exposed. Body burdens of organochlorine compounds in the West Greenland peregrines are not therefore sufficiently high to affect reproductive success; the pollution ecology of this population might be considered comparable to that of other arctic-breeding peregrines in the mid-sixties. These also had comparatively high organochlorine levels with no apparent effect on reproduction, but many eggs approached a critical level of shell thinning. Because of the close relationships found in other populations between DDE concentrations and the degree of shell thinning and associated reproductive failures, we conclude that a comparatively small increase in the DDE levels to which these birds are exposed would endanger the population.