(September 11, 2009) Two different species of Amazonian bird sing the same song, say scientists.

Over time, males of the two antbird species have evolved the same call to keep other males off their patch.

The researchers from Oxford University believe this is the first evidence of separate species having evolved the same territorial song.

They report in the journal Evolution that this is an efficient way to compete for resources without risking injury through fighting.

Both birds, the Peruvian warbling antbird and the yellow-breasted warbling antbird, are part of the same large family.

"But the fact that two species have the same song is actually a pretty weird finding," said Joe Tobias from Oxford's Edward Grey Institute, who led the research.

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