Well maybe it's local bias, but Little Gull is fairly readily seen in small numbers at most times of year wherever Bonaparte's Gulls gather in the eastern great lakes, with triple digit numbers passing through in spring (the high count last year was 158 at one site), all of which almost certainly breed around Hudson's Bay somewhere. From eBird it looks like it is reasonably regular on the eastern seaboard too.
Just looking at the list quickly, it seems like the population is comparable with code 2 Whooping Crane, and some of the other code 2 species seem like they also have similar status (e.g. Himalayan Snowcock, Yellow-footed Gull, some of the seabirds? My knowledge of ABA birds isn't good enough to really say though)
Looking at the code definitions and list though makes me realise that the classification is even more arbitrary than I thought, so I guess it doesn't really matter! In particular, there seems to be somewhat of a bias against northern birds - e.g code 2 King Eider, Sharp-tailed Grouse and particularly White-winged Crossbill seem to have much broader ranges and larger populations than many code 1 birds. I know their range might be less accessible, but it seems like this isn't supposed to be factored into the codes (e.g. Common Ringed Plover and Gray-headed Chickadee)
