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Ground-nesting birds, such as the diminutive grasshopper sparrow, are more elusive.

In particular, birds with relatively large territories that sing at medium to high mean frequencies—such as the grasshopper sparrow found in North America—were less likely to be heard.

They spent three years exploring captive breeding and rearing techniques on the eastern grasshopper sparrow, which is not classified as endangered.

But on May 9, 2016, the first four captive-bred Florida grasshopper sparrow chicks hatched in the Rare Species Conservancy’s laboratory, an event hailed as a major breakthrough.

The tiny Florida grasshopper sparrow, on the other hand, merely hopped out of an open screen and skittered along the ground, says Blackford, a U.S.