BC Rare Bird Alert: RBA: MCKAY'S BUNTING in Delta

At 2:15 pm on Dec 7, 2019 Mike Klotz found a pale bunting which he thought was a Snow Bunting at the Tsawwassen Ferry Jetty. At 4:15 pm on Dec 8, 2019 Liron Gerstman found the Bunting during a Coastal Waterbird Survey and noticed it was unusually pale. He sent me photos for a second opinion but I was away from a computer and phone access on vacation. Unfortunately this did prevent me from studying this properly and for getting the word out as widely as possible. Liron did let locals know about a pale Snow Bunting and eight people went to see it. He also reported it as a Snow Bunting to the RBA and it was placed on the Vancouver page as a Snow Bunting. The bird remained in the same location until Dec 12, 2019. It has unfortunately not been relocated since.

Map to location of where bird was seen on the south side of the ferry jetty HERE

With photographer permission I was able to send a series of photos to several experts including Jack Withrow - Collections Manager at the University of Alaska and to Jason Rogers (who wrote the ABA article on how to identify them). Both of them came back with several reasons as to why it was a female McKay's Bunting. Although we did not have a spread tail shot, we had a spread wing shot which proved diagnostic. Both Jack and Jason saw no reason to consider a hybrid and felt it was a pure female Mckay's Bunting.

Some points they made (shared with permission):

From: Jack Withrow (UA Museum, Collections Manager, Birds)

"This bird matches my conception of a female McKay's best, I have no reservations calling it that. In fresh plumage like this it's sometimes hard to assess what the mantle/back would look like once the fringes wear off, but this bird is just too pale to be a male Snow Bunting (even of townsendi) in that regard and almost certainly too well marked to be a "pure" hyperboreus if it's a male (which I don't think it is). The black on the flight feathers is just about gone by the 6th (from outermost) primary (this does not happen on female Snow Buntings), and the outer webs (and tips) of the primaries are extensively white (I think beyond what you would find on a male Snow Bunting), and it's just sorta on the pale end of the Plectrophenax spectrum (e.g., almost no rust on head/neck)."

When I asked Jack if photos were needed of the third retrix to be sure of the ID he said:

"I don't think it's necessary in this case, everything else points towards a female hyperboreus, possibly an adult based on the mostly white pp coverts, seemingly dark primary color saturation, and tail feathers that appear somewhat rounded and not very pointed."

Jack also provided more info on why the bird's wing pattern is diagnostic.

"My sense is that almost no one appreciates how much variation there is in Plectrophenax buntings (there is nearly a complete cline of phenotypes).

...your bird appears to have a wing that matches female hyperboreus best: it has a very jagged/stripped thing going on in the primaries where the black transitions to white (caused by the black extending further towards the bases on the outer vane with a concomitant extensive white edge to the outer vane) unlike all the male nivalis which are far more abrupt in this transition. The primary coverts are duskier at their bases than their tips, a pattern not seen in any male hyperboreus (at least in this series which includes many SY birds), but that matches many of the female hyperboreus quite well... I still think this is more hyperboreus than anything else."

From Jason Rogers:

"The spread-wing photo proved especially helpful here. The sharply-pointed scapular centres, brownish "black" areas, dirty white primary bases, mottled primary coverts, and fairly pristine flight feathers in combination safely identify this as a female Plectrophenax. With that established, no female Snow Bunting should appear this white. The outer primaries are extensively light, the secondaries appear immaculate, the outer greater coverts seem to have (at most) a touch of dark at the bases, and there's a strong contrast between the mantle and "back"- this is all consistent with female McKay's. Age is trickier, but I'm leaning toward adult based on feather wear and how white the primary and greater coverts appear to be. I see no reason to consider a hybrid at this point."

This is the 4th record for BC.