Is Chernobyl radiation really causing negative individual and population-level effects on barn swallows?

Møller and co-workers (Møller et al. 2007) observe an ‘elevated frequency of abnormalities in barn swallows (Hirundo rustica) at Chernobyl’ and ‘can think of no alternative explanations other than exposure to radiation that can have caused the observed patterns’. However, an obvious alternative hypothesis (e.g. Pikulik & Plenin 1994) is that apparent impacts on birds may be due to ecosystem changes resulting from the abandonment of contaminated land. In this and previous papers, Møller and co-workers downplay key limitations, namely: (i) probable confounding due to land use changes in the abandoned areas since the accident, and (ii) weak dosimetry and inappropriate grouping of ‘Chernobyl’ study sites. (i) The 1986 Chernobyl accident caused an area of approximately 30 km radius (the ‘30 km zone’) to be evacuated. Towns, villages and farms are abandoned, livestock were evacuated and former farmland is now rough grassland with shrubs and trees. Forestry has ceased and hunting is strictly controlled (though some poaching occurs). Since 1989, large increases in populations of large mammals (e.g. elk, Alces alces, wild boar, Sus scrofa, wolves, Canis lupus) and some rare birds (e.g. black stork, Ciconia nigra, white-tailed eagle, Haliaeetus albicilla) have been reported in the 30 km zone (Pikulik & Plenin 1994; Baker & Chesser 2000). In contrast, Pikulik & Plenin (1994) note population reductions in bird species commonly associated with human habitation. Barn swallows are commonly associated with human habitation and their population is influenced by farming practices (e.g. Møller 2001; Beecher et al. 2002 and see the electronic supplementary material). Møller and co-workers (Møller et al. 2007) discuss a ‘general deterioration of farming in Ukraine since 1990’ which ‘should have negative effects in both control and contaminated areas, predicting increases in the frequency of abnormalities’, but they do not apparently consider the abandonment of contaminated lands to be a potential confounding factor (apparently, two of their sites within, the others very close to the