Monday, September 27, 2010

Pigeon? Dove? What's in a name?

Rock PigeonRock Pigeon, Terrebonne, Oregon on 14 June 2008 by Greg Gillson.


Is there a difference between a dove and a pigeon? The short answer is no.

However, Peterson, Mountfort, and Hollom wrote in their 1974 A Field Guide to the Birds of Britain and Europe:
The terms "pigeon" and "dove" are loosely used and interchangeable, but in a general way "pigeon" refers to the larger species with ample, squared or rounded tails, "dove" to the smaller more slender species with longer, graduated tails.

In 1992 the British Ornithologists' Union changed the name of the Rock Dove and Stock Dove to Rock Pigeon and Stock Pigeon, respectively. This unified all the birds in the genus Columba with the name "pigeon." But, then, they also removed New World pigeons formerly in the genus Columba and put them into a new genus called Patagioenas. The American Ornithologists' Union followed suit in 2003.

How does that affect us in the Pacific NW? Well, if you have the "Big Sibley" guide printed in 2000, you will find a listing for "Rock Dove" as Columba livia. You will also find "Band-tailed Pigeon" as Columba fasciata. More recent field guides, such as the National Geographic (5th Edition) will list the new name "Rock Pigeon" still as Columba livia, and "Band-tailed Pigeon" now as Patagioenas fasciata.

Why change the common and scientific names and the order in which they appear on the checklists and field guides? These changes occur as scientists discover new relationships among birds.

That's the party line.

I sometimes joke that this is just a game and the scientists are just making it all up. In a way it's true. People like to pigeon-hole (pardon the pun) things to try to create order out of our complex universe. Nature is rarely so simple.

You may appreciate this blog post from 10,000 Birds:
Requiem for a Rock Dove

Sunday, September 19, 2010

Pirate of the seas: South Polar Skua

South Polar SkuaSouth Polar Skua, off Newport, Oregon on 11 September 2010 by Greg Gillson.


The big brute in the photo above is a South Polar Skua. I obtained this photo recently as the bird circled our boat, 35 miles offshore.

What is a skua? Skuas are dark seabirds with white wing patches. They are related to gulls. They have webbed feet and strong hooked bills. They are the size of the largest gulls, but heavier. South Polar Skuas differ from the other 3 or 4 species of skuas by being evenly dark, except for golden spangles on the hind neck.

Skuas are powerful and aggressive loners, attacking other seabirds. They steal fish from other seabirds--even if already swallowed!

More than once I have seen a skua pounce on a swimming Pink-footed Shearwater, grab it by the shoulders, and repeatedly dunk it underwater, trying to force the poor exhausted bird to regurgitate its last catch. In such a case, the skua may actually drown the shearwater and eat it instead.

Skuas are larger, bulkier, and more deliberate than the similar smaller aerobatic jaegers. While the Parasitic Jaeger reminds some of an ocean-going Peregrine Falcon, the South Polar Skua is more like a Red-tailed Hawk in comparison.

These birds are highly pelagic (found in the open ocean) and very rarely seen from shore in the Pacific NW. Most sightings here are at least 8 miles offshore, and most seem to be 20-40 miles distant from land.

The worldwide population of these birds is very small, only 5,000 - 10,000 breeding pairs. And their name is apt. They nest on the shores of Antarctica, where they victimize penguins.

While most of the population seems to remain in the southern hemisphere, some (perhaps mostly younger birds) undergo a migration around the entire Pacific Ocean. In spring they are found primarily in seas around Japan. They then circle around the Gulf of Alaska and show up off the coasts of the Pacific Northwest from August to early October. Then they are back in Antarctica to lay eggs in December and January.

Pacific NW ocean-going bird watching tours, called pelagic trips, rarely encounter more than half-a-dozen birds on a single day trip. In fact, one bird is probably the most frequent number seen, if any. That is why, though aggressive, it is always exciting to see one winging by.

And, if you're lucky, it may even circle the boat and allow you better views, and maybe a photo....

Monday, September 13, 2010

Chipping Sparrow

Chipping SparrowChipping Sparrow, Lost Lake, Linn Co., Oregon on 23 May 2009 by Greg Gillson.


The Chipping Sparrow breeds throughout the Pacific NW, but requires drier, open, park-like woodlands. Thus, it is usually rare along the wet coast and Coast Range forests, and on the more humid west slope of the Cascades.

It has the odd distinction of being found in the lower western valleys of Oregon and Washington, but not in the mid-elevation Douglas-fir and hemlock forests of the west slope of the Cascades, but then again very common high in the Cascades in the open lodgepole pine forests (as in the photo above). [See the species account in the Washington Breeding Bird Atlas.]

Most Chipping Sparrows winter south of the Pacific NW, though rarely some are found in winter in filbert (hazelnut) groves in the Willamette Valley. In spring, some may arrive in western Oregon as early as March, but the peak of migration is mid to late April through much of the Pacific NW.

In autumn, many birds form large flocks in open grassy clearings in the mountains. Few birds remain beyond early October.

In winter plumage they lose the chestnut crown and can appear similar to the rare winter vagrant Clay-colored Sparrow.

The song is a long (4-6 seconds), dry trill on one pitch. Dark-eyed Juncos can sometimes give a similar trill, but usually the junco is more musical and of shorter duration.

This species has declined in numbers over the past century, especially in towns. Loss of small farms and orchards, closing canopies in oak woodlands due to fire suppression, and increase of Brown-headed Cowbird nest parasitism are all likely causes.

In the past they lined their nests extensively with horse hair, and were even called "horse-hair birds." Having trouble locating Chipping Sparrows in your local area? Try finding a horse stable or one of the "gentleman ranchettes" that are popular today.

Friday, September 10, 2010

ID: Yellowlegs

YellowlegsGreater (right) and Lesser (left) Yellowlegs, Jackson Bottom Wetlands, Hillsboro, Oregon on 7 September 2010 by Greg Gillson.


Greater Yellowlegs is a common spring and fall migrant throughout the Pacific NW. It sometimes winters west of the Cascades in fresh water marshes. Lesser Yellowlegs is slightly less common.

Telling Greater from Lesser Yellowlegs is much easier when they are together, as in this recent photo above. When they are alone, or in single-species groups, it is harder to make this identification.

The key for lone birds is a comparison of relative bill length and shape.

The bill of Greater Yellowlegs, below, is rather thick (about as thick as the eye) for about half its length, and then appears to be very slightly upturned. Equally important, the bill length is about one-and-a-half times the length of the head in a straight line with the bill back from the gape, as shown in red:

In contrast, the bill of Lesser Yellowlegs, below, is rather thin and tapering throughout. The total length is just barely more than one head length, as shown by the red lines:

So, a bill length of one-and-a-quarter head lengths is a good rule of thumb for dividing between the species. Of course, there is a bit of variation and some birds might be too close to call.

Speaking of calls, this is when you need to use them. Greater Yellowlegs has a call that is a series of three loud piercing notes: tew, tew, tew.

The diminutive Lesser Yellowlegs has a correspondingly softer voice, and only one or two whistled notes: yip or yew, yew.

Monday, September 6, 2010

Violet-green Swallow

Violet-green SwallowViolet-green Swallow, Fernhill Wetlands, Forest Grove, Oregon on 29 July 2010 by Greg Gillson.


The Violet-green Swallow is the only swallow limited to western North America. In the Pacific NW they arrive in February and March and remain through September or early October. They winter from southern California and Arizona south to Middle America.

Similar to Tree Swallows, Violet-green Swallows differ by having a white face, lime-green back, and white rump divided in half by a violet strip of feathers.

These birds are very common throughout most of the Pacific NW. They occur from sea level to the tops of the mountains. They are equally at home flying over forests or towns chasing insects high in the air and uttering pleasant twittering notes.

They nest in crevices in cliffs, tree cavities, nest boxes, and holes in buildings.

In the fall, Violet-green Swallows migrate south in large flocks. Some times these flocks can number in the thousands. You may then notice them shoulder-to-shoulder on telephone wires, often near water.

Thursday, September 2, 2010

Oh, oh... Molt again

Great-tailed GrackleGreat-tailed Grackle, Hines, Oregon on 23 May 2009 by Greg Gillson.


Recently I was working through some photos from last year. Usually, after a photo shoot, I will immediately turn the best RAW shots into jpeg's and post those. Then, as I have time, I will work on the other shots and delete the (numerous) bad ones.

So, for instance, when I photographed this vagrant Great-tailed Grackle in the parking lot of a restaurant in Hines, Oregon, 15 months ago, I uploaded the best shot immediately. That left me with some shots like this one, above, that I am finally getting back to.

Even though I pulled the lens in from 400mm to 340mm it was not enough, as the bird was so close. As a result, the entire tail didn't quite make it into the frame. And there's this distracting yellow "something" pointing right at the bird's head. So, it is not a very artistic photo.

However, it shows something that I didn't realize at the time. This bird is almost exactly one year old. How can I tell? Molt limits.

Now I've been birding 38 years, and am just "getting into" understanding molt. So I sympathize completely if you don't find this as interesting as I do right now.

For most birders,... the brain fogs over at the mention of molt. -- Alderfer and Dunn, National Geographic Birding Essentials, 2007.

Last month I discussed this topic using a photo of a juvenile Brewer's Blackbird in molt. Today's post continues that discussion.

Even though this is a black bird, it is not completely one solid black color. Much of the plumage is rich black with glossy purple and green iridescence. However, many feathers on the wing and tail are dull brown.

Those dull brown feathers are retained juvenile feathers. Those are the first feathers this bird ever grew, probably in June of the previous year. Now, in the month of May, 12 months later, those original wing and tail feathers are quite worn. They contrast quite nicely with the glossy black feathers that were part of the pre-basic molt in the previous September.

In the next fall (2009) this bird will molt in new wing and tail feathers (and all feathers, actually) and be in definitive basic plumage. From then on, all through its life, it will undergo a complete molt each fall. Only during this first year and a half, can the age of this species be determined using molt limits.

Knowing the age of the bird tells us something about this vagrant. Even though this species is expanding its range, this young bird wasn't likely to be breeding this year. If it survives, it will likely migrate back south for the winter and possibly remain south to breed the next year (spring 2010).