The Cold War didn’t just restrict the movement of people, ideas, and trends in rock n’ roll, according to a new study–it also kept invasive species from moving into Eastern Europe.

Researchers looked at the number of non-native birds present in both Western and Eastern Europe over the past century. Before the Cold War restricted trade on the continent, Western Europe had 36 alien bird species and Eastern Europe had 11. By the time the Berlin Wall fell and the Iron Curtain crumbled, the number of alien birds in Western Europe had increased to 54, but the number in Eastern Europe had declined to five.

A National Geographic blog explains:

“Global trade is a real concern for invasive species, and the lessons we can learn from the Cold War offer a warning flag to developing countries that are now expanding in an international economy,” said Susan Shirley, a research associate in the College of Forestry at Oregon State University.

Although birds can fly over walls and through no-fly zones, the researchers say they usually stick to their native territories; however, when imported pet birds are released into the wild they can carve out a niche in the new land. The new findings, reported in the journal Biological Conservation, suggest that Eastern Europe may now be filling up with avian aliens. Anybody remember if Pink Floyd released any doves during that concert on the wall?

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Image: Wikimedia Commons