Birds of a feather

A near-universal symbol of happiness, these birds were so common in the early 20th century that they outnumbered robins.

But by 1970 the population of bluebirds in New York had fallen by 92% due to DDT and the loss of habitat that came with development.

In 1972, DDT was banned in the U.S. Across the Northeast, bird-lovers — including the folks at Mashomack — erected and monitored groups of nest boxes to replace the habitat lost to development, and bring back the Eastern Bluebird. And happiness.