Plover conundrum

Tuesday I found myself at Nanisivik Airport and with a half hour to spare I headed down to the former townsite. Earlier in the summer we had tried to get to the reliable spot for Common Ringed Plover (Charadrius hiaticula), but were foiled. One of the things that are done when they work on reclamation of the site is the culverts are taken out of the old roads, leaving large ditches in the middle of the road.  When we had tried to get to the plovers, which can be found at a series of lakes that served as Nanisivik's water source, our way was blocked by one of these ditches.

On Tuesday though I thought I'd try and find another route, and successfully found away there. I couldn't get as far as I'd like, but the way took me to the lake, until I was once again barred from going any farther by a ditch. I got out but nothing was moving. There were thunderheads in the distance, and for the second time this year I heard the rumble of thunder.  I stood a little longer, but my time was limited, and it had frittered away.

As I took  step towards the truck I heard a shorebird. I paused and listened, but heard nothing. Again as soon as I took a step it called, but when I paused it was silent. Suddenly there were two Common Ringed Plovers flying about me. Or were there?

Ever since I've been up here I've assumed that the plovers I was seeing were Common Ringed Plovers. All the literature I read, all the guide books, indicated that Common Ringed Plovers populated the north half of Baffin Island. Semipalmated Plovers occupied the south half, with some hybridization where the two ranges butted up against each other.

I snapped off some photos, but they were very active and always landed across some water away from me. This is the best of the bunch. I had no time to spare and headed back to the airport. When I got back I started looking closer at the photos, and doubt began to creep in.

The trouble with distinquishing between Common Ringed and Semipalmated Plovers is that they are essentially identical birds, reliably told apart in the hand. It was comforting to rely on distribution, that up here the birds would be Common Ringed Plovers, and I'd not have to do the hard work of trying to tell them apart.  But the birds in my photos looked more and more Semipalmated than not. The white patch behind the eye was almost absent. And when I enlarged the photos it seemed to me that there was a thin line of white above between the gape and the black loral stripe. Both are Semipalmated characteristics. Voice is apparently a reliable tool for telling them apart but, truth be told, I suck at identifying bird song.

The reliable defining characteristic is almost impossible to see in the field. Semipalmated Plovers have a small bit of webbing between both their inner and middle, and outer and middle toes. Common Ringed Plovers only have webbing between their outer and middle toes. With the absence of this evidence I fell back to the distribution. Breeding up here, the birds would have to be Common Ringed Plovers.

To be continued... (now with impossibly cute baby bird photos)