Wild Birds Deformed by Radiation

Barn swallows living near the contaminated Chernobyl nuclear reactor have a much higher frequency of physical abnormalities than do barn swallows breeding elsewhere in Europe. The deformities, which range from unusual color patterns to misshapen toes, beaks, eyes or feathers, have caused birds to die early.

Most of the 11 types of deformities documented were only found in swallows at Chernobyl, and not in birds from 220 km away or in Spain, Italy or Denmark. Birds with beaks that could not close or eyes that would not fully open were only picked up on open farmland located inside or less than a kilometre from the Chernobyl exclusion zone. Also encountered at Chernobyl, the distinctive, long outermost tail feathers of a few barn swallows were either bent or lacked functioning barbs, making the feathers look brushy.

Even when an abnormality appeared in birds from regions outside of Chernobyl, it occurred at a much lower rate. For instance, researchers found partial albinism, where some feathers that would normally be brown or blue are instead colored white, in nearly 14 percent of the Chernobyl swallows and at most in 5 percent of swallows elsewhere.

The defects are hindering the survival of barn swallows. Evidence for this comes from the decline in the frequency of deformities as birds get older. Malformations appear in 34 percent of Chernobyl chicks still in the nest, compared with 18 percent of adult birds. As well, survival rates of healthy adult swallows at Chernobyl is more than four times that of birds with abnormal features.

The researchers attribute the exceptionally high prevalence of abnormalities among the Chernobyl swallows to the radiation there that is 10 to 100 times the normal background levels. As the radiations levels have dropped from 1991 to 2006, so too has the frequency of deformed barn swallows.

This is the first time the effects of radiation contamination have been studied for a wild animal. The results refute the suggestion of some other recently published research that the high number of birth defects and other abnormalities found in people from the Chernobyl area is attributed to their high degree of poverty and stress, rather than excessive exposure to radiation.


A.P. Møller, T.A. Mousseau, F. de Lope and N. Saino. 2007. Elevated frequency of abnormalities in barn swallows from Chernobyl. Biology Letters. 3(4): 414-417.

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