Regarding last week's BRANT in Norwalk, CT: I have received opinions from two northwestern U.S. Brant experts. Both believe that the bird is likely a GRAY-BELLIED BRANT (the as-of-yet scientifically unnamed population that winters in the Pacific Northwest). The color and extent of the underparts, the shade of the upperpart color, the amount of contrast with the neck sock, and the broken necklace all seem to fit nicely within Gray-bellied Brant.
Very interesting stuff, but there is no way to eliminate an Atlantic x Black Brant hybrid. So it must be left as a probable Gray-bellied. This bird is likely too dark for Eastern High-Arctic Brant.
Several years ago Mark Szantyr photographed a likely GB Brant in Stamford, CT. Take a look at his photo (towards the bottom).