From left to right we have Veery (VEER), Gray-cheeked (GCTH), Hermit (HETH), and Swainson's (SWTH). Veery and Gray-cheeked Thrushes have no visible eye-ring. The Veery has a reddish-brown back and tail while the Gray-cheeked has an olive-brown back and tail. The Hermit and Swainson's have a visible eye-ring and a olive-brown back, but the Hermit has a contrasting reddish brown tail or "brown back and red tail configuration."
Pictured here are rear views (left to right) of Gray-cheeked, Veery, Hermit, and Swainson's.