Brightly coloured birds are among the species most adversely
affected by the high levels of radiation around the Chernobyl
nuclear plant, ecologists have discovered.
Abnormalities have been found in Chernobyl populations of Barn
The findings – published online in the British Ecological
Society's Journal of Applied Ecology – help explain why some
species are harder hit by ionising radiation than others.
Dr Anders Møller of the Université Pierre et Marie Curie
and Professor Timothy Mousseau of the University of South Carolina examined
1,570 birds from 57 different species in the forests around Chernobyl
at varying distances from the reactor. They found that populations of
four groups of birds – those whose red, yellow and orange plumage
is based on carotenoids, those that laid the biggest eggs, and those
that migrated or dispersed the furthest – declined more than other
The intriguing results centre on the role of antioxidants – chemicals
that help protect living organisms from the damaging effects of free
radicals. Certain activities use up large amounts of antioxidants. These
include producing carotenoid-based pigments for feathers, migrating long
distances and laying large eggs (birds lay down antioxidants in their
eggs, and will deposit larger amounts of antioxidants in larger eggs).
Møller and Mousseau hypothesized that because they had fewer antioxidants
left to mop up dangerous free radicals, these birds would most adversely
affected by exposure to radiation around Chernobyl.
According to Møller and Mousseau: “We found that bird species
differed in their response to radiation from Chernobyl. The strongest
declines in population density with radiation level were found for species
with carotenoid-based plumage, long-distance migration and dispersal,
and large eggs for their body size. All four of these factors are associated
with antioxidant levels, suggesting that reduced antioxidant levels may
cause population declines when species are exposed to radiation.”
Among the brightly coloured species most affected were orioles, blackbirds
and blue tits, while drab species like tree pipits, coal tits and chaffinches
were much less affected. Long distance migrants or dispersers that were
most affected included quails, orioles, hoopoes, blackbirds and robins,
while non-migrant or short-dispersing species like great tits, coal tits
and song thrushes were much less affected.
“This is the first study linking the effects of radiation on population
size of different species to antioxidant defence. Although all species
must cope with the potentially detrimental effects of free radicals,
because of their use of antioxidants, certain species are predisposed
to suffer most from these negative effects,” they say.
The results could have important implications for other animals elsewhere.
According to Møller and Mousseau: “There is large variation
in natural levels of radioactivity due to differences in the abundance
of radioactive isotopes, mainly in mountain regions where the underlying
rock reaches the surface. There are no studies of the biological consequences
of such variation in natural levels of radioactivity, but we suggest
that some of the consequences can be predicted from the present study.”
A P Møller and T A Mousseau (2007). Determinants of interspecific
variation in population declines of birds from exposure to radiation
at Chernobyl. Journal of Applied Ecology, doi: 10.1111/j.1365-2664.2007.01353.x
is published online on 11 July 2007.
Impact of Climate Change on UK Livestock
Natural England supports Year of Food and Farming
Young People Wanted for A Life On The Land
Traditional landscapes are changing says Natural England