Kirtland’s Warbler. Photo: Jon Dunn.

Spring, and a birder’s fancy turns to thoughts of warblers–in Central Park, Mount Auburn, the Institute Woods. But it is at such famous midwestern sites as Crane Creek, Tawas Point, and Point Pelee that the major eastern migration routes converge, and a good day can produce spectacular numbers and an impressive diversity of these “butterflies of the bird world.”

Among the most sought-after is Kirtland’s Warbler, a major target of Jon Dunn and Stuart Elsom‘s tour to Ontario, Michigan, and Ohio, which is underway even as I write. Famous for its rarity and its specialized habitat requirements, Kirtland’s Warbler has fascinated generations of American ornithologists and birders, among them Nathan Leopold–of Leopold and Loeb fame.

In 1922 and 1923, Leopold made two trips to the Michigan breeding areas of Kirtland’s Warbler. He published his observations in the Auk in 1924, the same year in which he and Richard Loeb confessed to the murder of 14-year-old Bobby Franks.

Leopold moved to Puerto Rico following his release from prison, and devoted the rest of his life to watching that island’s forest endemics. In 1963 he published his “Checklist of Birds of Puerto Rico and the Virgin Islands.”