Sunday, May 9, 2010

Swainson's Thrush

The spring migration continues to unfold slowly, with few birds at the banding stations.  Yesterday at dusk, a time when thrushes often visit the water feature, I ringed this second-year Swainson's Thrush.  You can identify the species by its tan spectacles.  Many birders are unaware that western races of Swainson's Thrushes have russet-colored backs.  The bird in the photograph has an olive-colored back, as would be expected in Minnesota.

The bird's age is known by the tan spots on its secondary coverts, just visible in the far right, lower corner of the photograph.  These coverts are left over from the bird's speckled juvenile plumage.  Older birds will either have molted into unspotted feathers or the tan spots will have worn away. 

This species winters from central Mexico to northern South America.  Erika and I saw them in the winter in the jungles of eastern Peru and Ecuador.  They breed in the northern Rocky Mountains and across Canada (and northern New England and northern Minnesota).  A Swainson's Thrush that I banded in Aberdeen, South Dakota, on 19 May 1985, was recovered on 11 April 1988 in Guatemala.

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