In the backyard... Rock Pigeon

Rock Pigeon, Portland, Oregon, 19 February 2011 by Greg Gillson.

 

You may find the Rock Pigeon in older field guides listed as Rock Dove. Their name was recently changed.

Regardless, this is the common domestic pigeon. They are widely raised as free-flying "pets." However, they are also widely distributed as wild birds, breeding on highway overpasses, large bridges, and tall city buildings. You can find them in city parks in nearly every city in the world. They also breed on cliffs in remote settings.

The typical, "natural," plumage is blue-gray with wide dark wing bars and white rump--as in the photo above. They have been bred to be various colors and patterns, and even with feathered legs or odd neck ruffles or crests.

Though many people view these birds as dirty city birds, I can't help feeling a bit of attachment as they fly by--thanks to my favorite childhood movie, Mary Poppins!

Now where did I put my tuppence?

Mystery Gull

Mystery Gull. 26 June 2011 at Newport, Oregon by Chet Conklin.

 

Every summer a few very white gulls--similar to the one photographed above and sent to me by Chet Conklin--show up and really confuse birders. [Thank you, Chet, for allowing me to use your photos.]

Gulls like this with a bit more pink on the bill are often reported as first-year Glaucous Gulls on the West Coast in summer. But with the dark bill, one may be tempted to match this with an illustration of a juvenile Iceland Gull!

This is not a Glaucous Gull nor is it an Iceland Gull. Here is why.

Ignore the bright white feather color for a minute and look at other field marks, especially shape. This fairly stocky gull has wings that extend barely beyond the tail (it is “short-winged”). The eye is dark, but I do see a paler iris than pupil in one photo. The forehead is rather flat and sloping. Legs and feet are pink. The bill is nearly entirely black, with pink gape (the corners of the mouth on the face) and a bit of paleness at the base of the lower mandible. The bill is heavy and thick, “swollen” at the gonys (where the red spot would be on the lower mandible, if this was an adult of one of the larger species of gulls). The bill is strongly hooked.

The body shape of Iceland Gull is long and thin, with long wings. The bill is small and petite on Iceland Gull, and doesn’t show such a strong hook. The head should be quite round. The Iceland Gull as a whole is “petite.” The bird in the photo is stocky.

The body shape is all right for Glaucous Gull, but the bill is wrong. The bill of Glaucous Gull is stout, but not overly wide at the gonys. The bill shape is not a good fit. More importantly, the bill of young Glaucous Gull is 3/4 to 4/5 pink with the outer 1/4 (or 1/5) of the bill sharply black.



Now go back to the color. Only the Ivory Gull is this all-over-white in normal plumage. Other white gulls will show darker gray or brown bars on the body plumage. So this gull is not in “normal” plumage.

One condition that could explain the white coloration is leucism, a condition where the feathers are unnaturally pale or even white. This is not albinism, as that condition is the lack of all color, which would include pale legs and bill, with an eye with a colorless iris—blood in the vessels making the eye appear pink. I learned recently it was incorrect to call a bird a “partial albino.” But this bird is not leucistic, either, as a close examination of the feathers will reveal.

Take a look at the top photo. Click it to bring up a larger view. Can you make out any nice-looking individual feathers?

Not really. The feathers are shaggy and many look more like hair. This bird is extremely worn. The feather vanes are mostly worn away and only the feather shafts remain. White feathers are weaker than dark feathers; they wear away more quickly. Even though this bird did get new head and breast feathers in April or May, this bird is in desperate need of new feathers again. But it’s not going to get any soon. Gulls go through a complete molt of all their feathers in fall, September through November.

Because this bird has a mostly black bill, we can say it was hatched 1 year ago, probably June 2010. After a few weeks in a downy state, it grew its first set of feathers. But juvenile birds do NOT turn around and molt right away again in the fall. Thus it keeps its first feathers (wing and tail) for over a year. (Body feathers—head, neck, breast, belly, back—are replaced also in spring.) Such one-year old gulls can become very worn and sun-bleached by summer—especially the wings and tail. Thus, this is a very worn and bleached gull.

Now that we know this vital piece of information we can go on to ask: "what species is this?" Well, the angled head and “monster” bill, as well as short wings and stocky body, point to the common West Coast gulls: Glaucous-winged Gull or Western Gull. Since the bird is so pale and worn—and paler feathers wear faster than dark feathers—we can say that this bird was originally quite pale. That makes this a first cycle Glaucous-winged Gull (some plumage descriptions of the past may call this a “first summer” plumage, in the sequence of downy, juvenile, first-winter, first-summer, second-winter, etc. until it becomes an adult in the 4th winter).

As noted earlier, many Glaucous-winged Gulls of this age have a much paler pink base to the bill (though uneven) and are reported as Glaucous Gulls.

There. More, I’m sure, than you ever wanted to know.

But in case you're not satiated yet, here is more:

A previous post on Glaucous-winged Gulls.

My pBase photo album images of Glaucous-winged Gulls.

Brown-headed Cowbird: "North America's most reviled native bird"

Brown-headed Cowbird, Hines, Oregon, 24 May 2009 by Greg Gillson.

 

Brood parasite: "Organisms that use the strategy... involving the... use of host individuals... to raise the young of the brood-parasite." -- Wikipedia.

The Brown-headed Cowbird does not build its own nest. Instead, it lays its eggs in nests of other birds. In fact, at least 221 known bird species have been hosts to Brown-headed Cowbirds. They usually only lay one egg per host nest. The host parent, often a much smaller species of bird, raises the cowbirds' young, usually to the detriment of its own young.

In "Brown-headed Cowbird: Villain or Scapegoat?" Birding 31:448–451, August 2004, author Stephen I. Rothstein argues that widespread population declines of host species by cowbirds is not scientifically supported. He believes that "North America's most reviled native bird" is unfairly blamed for declines in bird populations largely caused by habitat loss. Of course, we know who is responsible for altering and destroying the established natural landscape, now don't we?

So let's take a step back for a moment and view this bird without prejudice.

The Brown-headed Cowbird is a migratory blackbird. It arrives in the Pacific NW in April and remains into October. A few birds may be found in winter mixed in flocks with other blackbirds at cattle feedlots and similar concentration points.

The male has a black body and brown head; the female is slate-colored gray-brown. The young birds are brownish-gray with paler feather edgings. The bill is pointed and rather thick. Thus, as with female Red-winged Blackbirds, this combination causes some confusion with beginners in thinking juvenile cowbirds might be a sparrow or bunting.

 

Juvenile Brown-headed Cowbird, Hillsboro, Oregon, 13 July 2010 by Greg Gillson.

 

Two hundred years ago, this bird was restricted to the Great Plains. They followed great herds of American bison as they traveled, eating the insects kicked up as the huge mammals walked through the grass. Because of the nomadic lifestyle of the bison, cowbirds couldn't stay in one place to raise their young. Thus, the strategy formed of laying its eggs in other bird's nests.

With the subsequent cutting of forests, both in the East and West, the cowbird substantially increased its range. Cowbirds became common west of the Cascades only in the 1960's. In the past 50 years they have increased tremendously in the Pacific Northwest.

Male cowbirds give a rising squeaking call (starling-like) as they chase females in courtship. They also give a bubbly rattle call, similar to Bullock's Oriole.

Besides insects, cowbirds eat seeds. So, you may host cowbirds at your bird feeder--especially, it seems, east of the Cascades.

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Note: I write some of my "natural history" articles weeks in advance and have them published on a schedule. As sometimes happens in blogging about birds, another blogger posted an article on cowbirds while mine was in the queue (in news parlance, I was scooped!). Please read Dave Iron's account on Brown-headed Cowbirds that appeared on the BirdFellow blog on June 18.

Friday Foto: Black-throated Gray Warbler

Black-throated Gray Warbler, Beaverton, Oregon, 18 May 2011 by Greg Gillson.

 

Black-throated Gray Warblers are abundant migrants through the lowlands west of the Cascades and nest there and quite locally in juniper woodlands east of the Cascades.

We have discussed Black-throated Gray Warbler previously.

The bird that shouldn't be

If there really is such a thing, you should be able to call these crows in Victoria, British Columbia, Northwestern Crows. 16 September 2007 by Greg Gillson.

 

Regular readers of this blog know that on occasion I like to discuss field identifiable forms, or subspecies, of our Pacific Northwest birds. Such forms look and sound different than the "same" species elsewhere, and might be raised to full species status in the future.

However, this time, I'd like to discuss a species that is in your field guide that probably should not be there.

No, I'm not talking about the Pacific-slope/Cordilleran Flycatcher mess, or the 10 types of Red Crossbills proposed by call. I'm going to discuss the elephant in the room--the bird problem no one wants to acknowledge--the supposed "Northwestern Crow."

The range of Northwestern Crow (Corvus caurinus) is usually defined as along the immediate coastline from SE Alaska through British Columbia. Then its range is less well-defined, but into the Puget Sound region and northwestern Olympic Peninsula of Washington. You may find reference of birds to Long Beach and Vancouver, Washington, and even along the Columbia River from Astoria to Portland in Oregon.

As far as identification, it is supposed to be smaller than American Crow (Corvus brachyrhynchos) with faster wing beats and a deeper, raspier voice.

But guess what? There are pockets of crows along the Oregon coast, and even along the northern California coast, that are smaller than their counterparts 20 miles inland, and some are within the measurement range of Northwestern Crows (Measurements of Possible Northwestern Crows from Oregon. 1989. Range D. Bayer. Oregon Birds 15(4):281). They have more rapid wing beats and deeper calls. Are these, then, Northwestern Crows? This question has been asked for decades, with the usually accepted answer being "no."

The question of the status of Northwestern Crow in Oregon is somewhat of a template for discussing whether Northwestern Crow exists at all.

Northwestern Crows have been reported in Oregon since the time of Lewis and Clark. But Gabrielson and Jewett in their 1940 book Birds of Oregon had this to say: "Lewis and Clark... found crows abundant on November 30, 1805, at the mouth of the Columbia and listed them as Northwestern Crows, but unless the distribution of the two species has radically changed since that time, the Western Crow... was the more abundant species." Gabrielson and Jewett considered only 4 of the numerous crow skins taken in Oregon prior to 1936, and labeled Northwestern Crow, to actually be that species.

Subsequent evaluation of crow specimens from Oregon found none that could be clearly assigned to Northwestern Crow, and many were definitely female and juvenile American Crows. The book, Birds of Oregon: a general reference (2003, page 620-621, Marshall, Hunter, Contreras, editors) summed it up: "Given the lack of reliable specimen evidence, it cannot be shown that the Northwestern Crow has ever occurred in Oregon."

A study by D. W. Johnston in 1961 (The biosystematics of American Crows) found that Northwestern and American Crows were very closely related and may be conspecific (the same species).

The National Geographic book, Complete Birds of North America (2006, Jonathan Alderfer, editor) has this to say about the ID of Northwestern Crow: "Unfortunately, [C. b.] hesperis [Western American Crow] found in the Pacific Northwest is identical." That's pretty damning. As is: "Field identification within the suspected range of overlap in WA is probably impossible."

Thus, it is apparently only range that separates American Crows and Northwestern Crows. If you are in SE Alaska or the coastal slope of British Columbia and Queen Charlotte and Vancouver Islands, the crows are Northwestern. Inland in British Columbia and the rest of the West, including Oregon and California, they are American Crows. If you are in Puget Sound or on the Olympic Peninsula of Washington, well, then, I guess you can call them whatever you want.

That doesn't sound like a "good" species to me. Does it to you?