Maeve,
This is all I could find on the second site : "SWAINSON'S THRUSH (Catharus ustulatus) Common to abundant migrant Generally this species is the most common of the migrant thrushes; it is also the one most likely to be heard singing during spring migration. The song is a set of rising, flute-like notes, usually given soto voce during migration. On occasion, these thrushes are present by the hundreds in the coastal woods. There are three startling winter records, both on Venice Christmas Counts, and in each case great care was taken to make sure that the bird was not a Hermit Thrush".
But there is so much on the site that I could easily have missed it.

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