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"The existence of 'locally adapted' populations implies that natural selection has shaped the genetic makeup of song sparrow populations across their range, enabling individuals to survive and reproduce in drastically different climatic conditions," said Carbeck.

In New York, researchers found chickadees and song sparrows that ate insects contaminated with PCBs along the Hudson River sounded a bit different than ones in uncontaminated areas in the Adirondacks.

Adaptable and variable, song sparrows can be found in abundance in overgrown fields, wooded edges and backyards, where they are common visitors at bird feeders.

A heron cruised overhead, and a song sparrow belted it out like a diva.

How song sparrows use their song to warn off intruding song sparrows has been studied by researchers at the University of Washington.