(Catharus ustulatus)
Summer
Winter
HABITAT: Primarily spruce-fir forests of North and West; also deciduous riparian woodlands in California
DESCRIPTION: Uniform olive-brown above, varying geographically from olive to ashy brown; buff-colored eye ring and buff color on face, throat, and breast, with brownish-black spots on breast; whitish belly
In Costa Rica you could hear him warming up during April, preparing for the trip north. He sings in migration, the unmistakable song a sure sign that he and his kin are passing. Once he arrives on his breeding territory, though, he’s almost songless, instead mainly calling for a week or even two. There’s the sharp whit, just a single sharp note, and the whitburr, the whit combined with a lower, drawn-out buzzy note. Listen also for a peeep, similar to the sound made by a spring peeper.
But after some time the singing resumes, and sing he does, nine to ten songs per minute. The prelude for each song is low, the softest of throaty notes, but then he rises to the first spiraling phrase. Hear it rise and fall, and then he rolls on to the next and the next, each phrase spiraling, each higher and louder and often longer than the one before. Each phrase is a microcosm of the larger song that itself is a smooth, windy, fluty, spiraling progression upward toward the heavens. Wait a few seconds and he delivers again and again, each song in the same overall form.
If you were to have thrush ears, you’d hear that he has from three to seven of these magical songs. Concentrate, comparing each song to the next, and eventually you realize that successive songs usually differ ever so slightly. Sometimes he sings in a highly predictable order, such as A B C D E F A B C D E F, but other times he mixes up his songs, as in A B C C D E B C F D A B . . . .
This ethereal spirit of spruce and fir woodlands sings well before dawn and well after sunset, his voice lingering in the fading summer twilight when most other birds have stopped singing for the year.
Male’s songs, spiraling upward Variety of calls 
