Thursday, September 15, 2011

Identifying Cassin's Auklets

You will likely have to see hundreds of Cassin's Auklets before you see one this well. Photo 8 August 2009 by Greg Gillson.

On the water, Cassin’s Auklet is a pudgy, round, gray ball. It is similar in size, shape, and coloration to a tailless juvenile European Starling, or a dark gray rubber bathtub duck. The head rests on the front of the body with no visible neck. The bill is rather short and thick at the base. The breast is dark to the waterline, fading gradually along the sides to the pale under tail. The white eyes and eye crescents are surprisingly visible.

This is the view as shown in the field guides. Go ahead and look, but you'll never see one like this. Why? The bird above was photographed at 1/1000th of a second. Your eyes don't work that fast and these twitchy little birds don't hold still very long! Combine that with rough seas and a bouncing boat, add some wave splash and spray, magnify all that movement by 7 or 8 times (the magnification of your binoculars), and it's no wonder that even after several pelagic trips where Cassin's Auklets are recorded, many seabirders still haven't gotten a good look.

When The Crossley ID Guide was published earlier this year, I discovered that Richard Crossley created an entire book of photos I had been deleting! His book showed only a very few birds at close range and tack-sharp focus. Instead, he showed birds as they actually appeared in the field--at odd angles, flying away, half-hidden, far away, and blurry!

Pfft. I can do that!

So here is the identification description of Cassin's Auklet, edited from my never-to-be-published book, the working title of which is: Seabirds of Oregon: A Field Guide to the Tails of Fleeing Alcids. It is accompanied by several realistic photos of Cassin's Auklets--yes, at odd angles, flying away, half-hidden, far away, and blurry!

Cassin's Auklets are widely distributed from near shore to far offshore. Usually, though, the distribution is uneven. During a typical pelagic trip the boat may travel through “bands” of birds, when a dozen or more may be seen in a 10-minute period, separated by hours with none.

Cassin's Auklets spend much of their time diving underwater for krill. Like other alcids, these birds are skittish and flee the oncoming boat. Thus, look for birds taking off several hundred feet in front of the boat. If the birds were under water as you approached, they may pop up for a breath and dive back down, with only their head coming out of the water. All you may see is a splash and a brief instant of feet sticking out of the water.

Cassin's Auklets run on the water into the wind to take flight. Fleeing in front of the oncoming boat they flap their wings frantically, like oars rowing in the water, and run strenuously on stubby legs, creating an impressive long trail of splashes.

All this flailing effort does not necessarily lead to flight. They may just have gorged on food. They may be molting flight feathers. The water may be too rough. The boat may be gaining on them too quickly. Cassin’s Auklets often have trouble getting airborne. They may bounce off the water several times before gaining enough speed and elevation to rise up above the small wavelets that reach up to slap them down again. As the boat gains on them they often give up their doomed efforts at flight and dive under the water to safety.

If, by some miracle or accident, the bird does become airborne, the Cassin’s Auklet in flight is a flying potato. It is a tailless, headless blob. The whirring, small, rounded, Popsicle-stick wings are just a propeller-like blur. Flight is relatively slow and fairly low along the water, no higher than necessary to clear the wave crests.

A flying potato with whirring Popsicle-stick wings.

In low-angle morning or late afternoon sunlight the underparts can appear surprisingly white. In addition, a silvery sheen may show in the middle of the underwing panel if the observer is looking directly at the side of a well-lighted bird in flight. Under these conditions the bird may be mistaken with Ancient Murrelet. Pale feather-wear crescents behind the wings (where the folded wings lay) give the appearance of pale flank or rump patches on birds flying away.

Cassin’s Auklets, and alcids in general, are more visible on West Coast pelagic trips in late afternoon returning to port. Often the seas appear smoother traveling east with the wind and waves, and with the sun or bright skies to your back. At other times, it is easier to observe birds on the water between 20 and 45 degrees on either side of the reflected sun. The seas at that angle appear very pale and bright, and the dark alcids show up better there than at 180 degrees from the sun where the seas appear dark. So the place to look is in the smooth, bright water, but not directly into the sun.

The tails of fleeing alcids

If you want to try your luck onshore, alcids, and seabirds in general, approach nearer to shore at night and move offshore first thing in the morning. The best time to watch seabirds from shore is just after sunrise, with the sun to your back. Cassin's Auklets are especially numerous in September and October off the shores of the Pacific Northwest. Search for a slight headland near the water, such as at Boiler Bay, Oregon.

1 comment:

  1. The "flying potato" ! I'll bear this post in mind in the unlikely event of one turning up here on the opposite side of the pacific !