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

Møller and co-workers (2007) observe an "elevated frequency of abnormalities in barn swallows 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 and Plenin, 1994) is that apparent impacts on birds may be due to ecosystem changes resulting from the abandonment of contaminated land.