Source: BBC Earth News
The finding comes from a study of 550 birds belonging to 48 different species living in the region, published in the journal PLoS One.
Brain size was significantly smaller in yearlings compared with older birds.
Smaller brain sizes are thought to be linked to reduced cognitive ability.
The discovery was made by a team of researchers from Norway, France and the US led by Professor Timothy Mousseau from the University of South Carolina, US, and Dr Anders Moller from the University of Paris-Sud, France.
In April 1986, reactor number four at the Chernobyl nuclear power plant exploded.
After the accident, traces of radioactive deposits were found in nearly every country in the northern hemisphere.
An exclusion zone has since been set up around the site of the accident.
However, scientists have been allowed inside to gauge the impact the radiation has had on the ecology of the region.
Last year Prof Mousseau and Dr Moller published the results of the largest wildlife census of its kind conducted in Chernobyl – which revealed that mammals were declining in the exclusion zone surrounding the nuclear power plant.
Read more: Chernobyl birds are small brained