The most serious losses in the species -- the slender-billed curlew, the spoon-billed sandpiper and the golden bunting -- occur while the migrating birds are in transit, especially in winter, Vitaly Zubakin told RIA Novosti Thursday.
The number of sparrows in Russia has also been declining, Zubakin added, but noted that "this is an all-European trend."
While some species are at risk of extinction, at least 10 new bird species have appeared in Russia in the past 20 years, he said.
That was likely due to a change in migration paths and "climatic imbalances," he said.
The Russian Bird Protection Union, established in 1993, unites some 2,000 ornithologists and thousands of bird lovers in Russia, RIA Novosti said.