October 2nd, 2016: Poring over plovers at Boundary Bay
I try never to miss a chance to head south to Boundary Bay, especially with a friend and a great (loaner) scope during shorebird migration!
This is always the best time to find Asian vagrants and other late migrants in and around massive flocks of Black-bellied Plover and any peeps that are hanging around. Mostly we were here to look for Golden-Plovers—American and/or Pacific—that are often mixed in with the hundreds of Black-bellied Plover around this time of year.
Planning for accurately the tides is an art that I have not yet mastered, but we at least knew roughly when and where to be. We arrived ahead of the late afternoon high tide, which we knew would be low enough not to put the water right up to the dyke (and the shorebirds into some inland field or other). We also knew we’d only have about an hour on the rising tide before the sun was close enough to setting that IDing Golden-Plovers among the Black-bellied would be nearly impossible: the best way to quickly find a non-breeding (which these would be) Golden-Plover is to find the more golden or yellow-y birds among the mostly gray, non-breeding Black-bellied and to look for variations in posture and what I think of as “sweep” (just the extent to which especially shorebirds taper toward their tail). Arriving at the base of 104th Street in Delta, the plan was to locate a (or the) large flock of Black-bellieds and start combing through them with our borrowed Swarovski scope. Fortunately, we found a good flock around 96th Street: sometimes they’re out toward 112th or well east of 96th, so this saved us some walking time.
We started scanning through the flock and quickly located a group of Golden-Plover! 7 to be exact! This was good, but now we had to figure which Golden-Plover they were. This is where the real birding fun (for me anyway) begins. These IDs are still very challenging for me, but I’ve picked up a few tricks over the past few years that make initial potential IDs a lot easier.
Without launching into a “how-to” diatribe on distinguishing these birds (there are better places to find that info), my first go to for separating this difficult pair is GIS (General Impression of Species): I look at its posture, facial expression, sweep, and the number of primary tips that extend past the tertials. I find that this first look gives me a good “in” for some effective differentiation between non-breeding or juvenile American and Pacific GPs. The posture is a big one for me initially: Pacifics often appear more alert, “taller,” and with a seemingly sharper slope down the forehead, perhaps largely because of this posture. Americans, however, often appear slightly hunched to me. This posture also seems to contribute to an overall impression of curiosity and meekness for the Pacifics, while the Americans look a little more confident and perhaps less vacant to me.
Of course, these aren’t really field marks, but the last one is: apparent length. Perhaps the quickest way to almost certainly distinguish between the two is to observe the projection of primaries past the tertials when standing (4–5 for American; 2–3 for Pacific). This ID works because the Pacifics have shorter wings and longer tertials, which result in only three primaries extending beyond the tertials and wings that extend only to the tail or slightly beyond. Americans, by contrast, usually show four primaries past their shorter tertials and wings extending well beyond the tip of tail in most cases. I find that the apparent length of the bird—or the degree to which the bird is streamlined or “swept back”—will often give me a solid initial ID that I can corroborate by counting primaries. Sometimes, however, birds don’t quite fit this mould conclusively, or they simply won’t give you a side view. This time we were lucky though: of the 7 GPs we found, we both agreed that, with reasonable certainly, 3 were American and 2 were Pacific; the other 2 could potentially have been either. Gotta keep practicing!
As the sun set, we tried to get a good count of other birds hanging around and were lucky to find many other shorebirds: Black-bellied Plover (of course), Killdeer, Sanderling, Dunlin, Pectoral Sandpiper, Western Sandpiper, Short-billed and Long-billed Dowitchers, and Greater Yellowlegs. We also saw a Merlin and Peregrine Falcon zip past, but, fortunately, we’d been able to count birds before the falcons scattered them (eBird list).
Once the sun set, the soundscape was dominated oddly by the sound of the thousands of American Wigeon and Northern Pintail dabbling away: thousands of bills closing around their late meals. But it was a clear night! (That never happens in Vancouver.) That meant we could point our birding scope upward and look at the stars. The detail on the moon was particularly stunning, but at this time of year, we were also able to get a fantastic view of Saturn with its rings showing clearly. Don’t forget: scopes aren’t just for birding!
The Golden-Plovers are both fascinating birds with some interesting distinctions. The Pacifics are my favourite because of their appearance in all plumages, because of their curious expression, and because they don’t often find their way anywhere other than the west coast in North American. Once upon a time, American and Pacific GPs were considered subspecies, but it turns out that they prefer slightly different nesting habitats—rocky, vegetated tundra and not-so-rocky, vegetated tundra, respectively—and do not interbreed (their only breeding range overlap occurs in Alaska). They also fly markedly different migration routes: Americans fly down either North American coast (or down the central-east) well into South America, while Pacifics make it only as far as coastal California, but spread all the way across the Pacific Ocean, from California, to Hawaii and Asia, and even northeastern Africa!