A "yellow-bellied" kingbird with a gray head with blackish mask through eye. Bright olive-green back - slightly darker wings with broad buff-ivory edges to wing coverts and tertials, brown notched tail with no sign of white outer edges to outer retrices or dull lighter tip( as in Western or Cassin's Kingbirds, respectively). Throat light whitish. Breast and belly much brighter yellow than normally seen on either Cassin's or Western Kingbird. Larger bill, especially deeper, than expected for either Cassin's or Western. DID NOT CALL.
An exact count. Foraging mostly low over the water. They were pretty far out when first seen so I stayed with them for about 10 minutes as they came closer, to ensure ID. Dark bluish above and white below with no white coming up above eye or from the vent towards the rump (as in Violet-green). Some birds had more of a bluish tint above and some more of a brownish tint, but all had clean white underparts. At one point a few were close enough to hear them call a fast "chidilip" is my best phoneticization. As any swallow in December in NM is unexpected I spent some time with these birds.
All heard calling, six with typical doubled "chimp" note (rather than Wilson's Warbler like calls, eliminating Pacific Wren). Two calling a chatter trill that I've only discovered was a Winter Wren call within the last few years. At one point there were three calling from different locations while I was standing in one spot! Astounding number - all in wet impoundments with salt cedar as the dominant cover type. One seen - a stub-tailed brown wren with a lightish tan supercilium and the most rufous portion was the tail.