The limitations of Structure

(Written with some irony as I'm a Structural Biologist so quite a firm believer of the importance of structure at the atomic level).

The publishing of the O'Brien-Crossley-Karlson Shorebird Guide brought with it some fanfare of improved methods of ID by "birding by impression". I'm perhaps not as impressed as I could be by that idea, because I don't think it's novel - anyone that's spent any time birding is using structure (shape and posture, but also intangibles of behavior) anyway.

Since I belong to the often thought-provoking BIRDWG01 "Frontiers of Bird Identification" email list it's often very interesting to think about the discussions on there. In particular it's apparent that the structural appearance of a bird is often very heavily influenced by the posture that the photograph captures. It may be "typical" or "atypical" viewed through birders' eyes. I've developed an internal idea about how birders select ID point, which in terms of structure involves discarding a whole range of ambiguous views (or perhaps integrating them mentally) until a distinctive view is found from which one can make the ID. A photograph presents only one or a small number of views, and mayhem seems to sometimes break out by experienced birders trying to hammer the square peg into the round hole: an anomalous view of a typical species.

Although color perception may be skewed by lighting in photographs (or to a lesser extent by post-processing), I find that structure is especially vulnerable to this. I've seen shorebird structure vary all over the place in a series of photographs. To whit: two recent BIRDWG01 discussions on a bright alternate White-rumped Sandpiper from Canada and a first fall immature Sanderling from Bolivia in prebasic molt. In both cases one of the strongest proponents of structure as a primary ID point identified the former as Western Sandpiper and the latter as White-rumped. Whoops. Particularly in the latter case where I was induced to go dig out my own photos of the White-rumped & Sanderling group to check my overall impression (color and bill structure) against the photographs. And it looked even more like a Sanderling after that exercise than it did on my first impression. Plumage coloration and pattern were definitively Sanderling from my perspective.

Which leads me to suggest: structure is overrated, particularly when identifying from photographs. Often very important, sometimes definitive, but also perhaps overrated and certainly not revolutionary. Birding has been going on for too long, practiced by too many people, for anyone to come along with revolutionary ID points across entire classes of birds. While genetics may radically revise how we view species distribution and what it means to be a species, I somehow doubt that morphological considerations are going to overwhelm those of plumage color and pattern any time soon.

Princeton, August 27th and 29th

I did a little walk without optics along the gravel road at the Institute Woods on Friday after work. Migrants were pretty much absent - the Eastern Wood-Pewee that was calling may have been a resident bird. However on my way back to the car there was a good find - two Pileated Woodpeckers feeding fairly close to the road. Once you track down the wood chopping sound there's not much you can mistake a Pileated for.

On the morning of the 29th I returned with optics to check out migration but it was still deathly quiet. I found a Scarlet Tanager along the road, Pewees were calling and that was it again. At the pond Red-winged Blackbirds were numerous, probably roosting there, and two slimmer tan icterids took off heading away from me - probably Bobolinks. Best bird was a Ruby-throated Hummingbird that shot past me as I was standing on the observation platform (literally a few feet to my left) and kept heading south-west. The loud drumming from deeper in the forest sounded big enough that it was the Pileateds again, but I didn't see them this time.

Brigantine NWR, August 28th

Making a little of a lethargic start I opted to go check out shorebirds at Brigantine NWR, with high tide expected around the middle of the day. There was a large flock of Tree Swallows at the Gull Pond tower turn-around but the tower was under construction.

Recent rain seem to be reflected in the pools being relatively high on water, although the north-western pool looked like it had been drained down to provide more shorebird habitat. I came away with not too much diversity, at least in part because I went around prior to high tide and because the driest pool put the shorebirds deep into the heat haze. Best shorebirds were a couple of Pectoral Sandpipers, missing the Buff-breasted and Avocets seen later in the morning. Spotted Sandpiper, both Yellowlegs, Willet, Semipalmated Sandpiper (abundant), Least Sandpiper, Black-bellied Plover and Ruddy Turnstone rounded out the total. Ospreys and two Peregrines were the raptors seen. At the "tern sluice" there were no Common Terns but a nice extra were two juvenile Least Terns and a molting adult - a species I see infrequently there. Other terns included abundant Forster's, a few Caspians, and Black Skimmer. Two Blue Grosbeaks at the dogleg and a fast moving Ruby-throated Hummingbird were two other notables.

Jamaica Bay, August 20th

This was a high tide mud-crawling exercise late in the day on a Friday, and as I walked out onto the north end of the East Pond a young Peregrine had scared all the shorebirds into the air - a large chunk of them settled down in front of me so I didn't move more than 50 yards in the next three hours. The diversity was modest because of that.

Best birds were good numbers of White-rumped Sandpipers - all adults, followed by a flock of 9 Stilt Sandpipers - also all adults. Juvenile Semipalmated Sandpipers were relatively uncommon although the adults were by far the most numerous species present.

Double-crested Cormorant
Great Egret
Snowy Egret
American Black Duck
Green-winged Teal
Peregrine Falcon
Black-bellied Plover
Semipalmated Plover
Greater Yellowlegs
Lesser Yellowlegs
Semipalmated Sandpiper
Least Sandpiper
White-rumped Sandpiper
Stilt Sandpiper
Short-billed Dowitcher
Forster's Tern
Barn Swallow
Northern Waterthrush

Jamaica Bay, August 7th

My first foray into NYC for fall migration corresponded to a morning high tide at Jamaica Bay WR where I was interested mainly in shorebird photography and not pushing my luck with elevated temperatures.

The East Pond had moderate levels of exposed mud which were still quite wet and not all that green yet at the south end. Apparently at the north end it's still quite muddy, but the forecast looks generally dry so the odds are that it will draw down yet further.

Shorebird diversity was modest, but then again I didn't go even as far as the Raunt. Semipalmated Sandpiper (adults only) was the most numerous, Semipalmated Plover (adults), Least Sandpiper (adults+juveniles), Lesser Yellowlegs (juveniles) and Short-billed Dowitcher (adults+juveniles) were around. There was a good tern showing: Forster's, Common, Least and juvenile Black. There was also a good selection of herons: Great Blue Heron; Great Egret; Snowy Egret; Tricolored Heron; Green Heron; Yellow-crowned and Black-crowned Night Herons (Yellow-crowned being particularly numerous). Boat-tailed Grackles were in predictably heavy molt. The best bird was a distant look at the American White Pelican which has lingered here and remarkably not my first one at Jamaica Bay. Over on the West Pond nothing much was happening although I did add Spotted Sandpiper, American Oystercatcher and Greater Yellowlegs. Diversity should increase as the month draws on, although more widely-ranging birders had more luck than me with the less common shorebird species.

Swallows and Swifts

A nice find on returning home last night was a group of Chimney Swifts and swallows feeding over a (presumed) insect swarm across the road and doing passes over my property. A couple of large dragonflies were also hunting. At first I assumed it was just two or more Barn Swallows, but after fetching binoculars I saw two Northern Rough-winged Swallows perched on one of my Silver Maples. Northern Rough-winged is a new yard bird.