In flight shows the white edges to the outermost tail feathers and dark tail contrasts with paler back.
There's a Western Kingbird causing excitement in NH, being seen at Rochester Wastewater Treatment Plant, (which is closed on weekends and if you visit, check in first), map (furnished by Steve Mirick) to kingbird is here. There are very few records for this species in NH, that's why birders are excited. A nice photo of the NH bird (by Jason Lambert) can be seen here.
To follow the sightings, see NHBirds listserve here.
The Western Kingbird is a type of flycatcher whose range is in the West, but it's a common vagrant (bird who wandered out of range) to the East. They have a yellow belly, gray head and breast, and a dark tail that contrasts with the gray back. The tail has white edges.
We were lucky to have seen a Western Kingbird on our southern NH property on August 31, 2003 when our friends from FL, Lois and Leon White, were visiting. It was seen well by all of us. Always nice to produce a rare species for your area when birding friends are visiting. Above photographs are of a Western Kingbird I photographed in Sanibel, Florida in Jan. 05.