A Song for July 19

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Juncos are New World Sparrows (Family Passerellidae), but they live in and around forests, where other sparrows are few and wood-warblers (Family Parulidae) are many. Still, they are so common that one can train oneself to remember that a slow trill of metallic but musical notes is not a warbler, but "just a junco." Nevertheless, today's song, a series of buzzy notes, will give one pause, and has led me on many a wild goose chase, in Oregon, North Carolina, and in between. Even when experience reminds you that juncos across the continent have song-types like this, the imperative to check it out can be irresistible.

Juncos across the continent sound exactly alike, as far as I can tell, but they do not look alike. The Oregon Junco has a black hood, brown back, and tan flanks. The Carolina Junco replaces all those color patches with gray. The genus Junco breeds from Alaska to Costa Rica, and has 12 field-identifiable forms, but no two of them overlap in the nesting season, suggesting similar ecological requirements. They are one and many at the same time. In New Mexico three forms winter together in mixed flocks, as though one species, yet little gene flow occurs between the forms. And all six kinds of Junco that nest (and winter) in the U.S. and Canada are less than 18,000 years old, a blink of the eye in evolutionary time. This has all been discovered by Borja Mila and his colleagues, using molecular techniques.

Anyone interested in Southern Appalachian biogeography has heard of Mt. Rogers. It is the highest point in Virginia, and is crowned with spruce-fir forest. But that forest is reached only by a hike, so I drove to the top of nearby Whitetop Mountain to get my first taste of the Grayson Highlands, the massif that includes Mt. Rogers. The common spruce-fir birds were there -- juncos in numbers, Red-breasted Nuthatches, and Golden-crowned Kinglets. The surrounding grasslands had Vesper Sparrows, also a high elevation species in the Southern Appalachians. And I heard a Yellow-rumped (presumably Myrtle type) Warbler. Not bad for the second half of July.

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Nathan D. Pieplow. 2017. Peterson Field Guide to Bird Sounds of Eastern North America. Houghton Mifflin Harcourt.
Nathan D. Pieplow. 2019. Peterson Field Guide to Bird Sounds of Western North America. Houghton Mifflin Harcourt.
Donald Kroodsma. 2005. The Singing Life of Birds. Houghton Mifflin.