Hermit Thrush taxonomy is complicated and unresolved, with roughly 10 races. Whatever the finer divisions, they do resolve into three basic groups: the bright Eastern forms, with their tawny flanks; the grayer, paler subspecies of the interior mountain West; and the more variable races of the Pacific Coast.
When we're used to seeing one of the races, a different form can easily fool us into thinking we're seeing a different species of thrush. Look for the warm reddish tones on the tail!
Auduboni is the race that breeds in the high mountains of southeast Arizona, where their ethereal songs lend a special magic to dawn and dusk in the forest. Other than that, I haven't fit our birds into their appropriate groups yet, but have noticed this: the thrushes that overwinter are very pale, with light spotting on their breasts. Here is a photo from today's walk of our familiar race.
A paler, local race of Hermit Thrush (Photos by Narca)
And for the past three weeks or so, this darker, brighter, more heavily spotted migrant has been coming through. These photos, also taken today along the trail from Sunny Flat Campground in Cave Creek Canyon, show the migrant Hermit Thrush.
If any Hermit Thrush expert would like to shed light on exactly what we're seeing, please do!
Whatever the name of the race, the Hermit Thrush's song is arrestingly beautiful. Listen for it during nesting season!