The Blue-winged Teal is rare in Massachusetts in January as evidenced by the eBird frequency and Bird Observer records (only 1 since 2005). Experienced birders have told me that while there are other records not posted in these sources, they are indeed few and far between. Oddly, however, this year I'm told that there are currently 7 on Nantucket and 3 at Marstons Mills on the Cape. So while it's not super rare, it is definitely unusual and none of the January records mentioned have been for locations in Plymouth County.

My guess is that this individual was injured (or shot) during migration as indicated by the damaged right wing in the first photo. It can definitely fly (perhaps healing) as it flew in to where I photographed it (in Plymouth Harbor close to the little grassy park just south of the Mayflower and Plymouth Rock) and joined a group of 4 female Buffleheads which it proceeded to chase around. The last photo shows an irritated Bufflehead just before it dove and swam away from its surface-bound harasser!

The field marks are best seen in the first photo. The swimming shots show just the tiniest glimpse of light blue in the center of the coverts.