Reduced abundance of raptors in radioactively contaminated areas near Chernobyl

The negative ecological effects of radioactive contamination around Chernobyl have recently been suggested to be moderate and declining because of an increasing number of anecdotal observations of several species of rare animals including predators. However, these claims were not based on empirical evidence. Radionuclides show bio-accumulation with trophic level, and the abundance of birds is depressed in radioactively contaminated areas around Chernobyl. Therefore, we predicted that birds of prey should be less abundant with increasing levels of radiation. Here, we use our long-term field data from 1991 to 2007 in three different analyses based on observations of raptors using standardized point counts, censuses during capture of barn swallows Hirundo rustica that habitually give alarm calls when a raptor is present, and line transects while driving on roads. Analyses suggest that the abundance of birds of prey is reduced in contaminated areas, and that there is evidence of a recent increase in abundance of raptors in less contaminated areas, but not in the most contaminated ones. Our findings suggest that birds of prey that are top level consumers in ecosystems suffer from reduced abundance in radioactively contaminated areas.