Troglodytes troglodytes

The Changes Are In

26 July 2010 Nathan Pieplow

It’s July, and that means it’s time for the annual update to the American Ornithologists’ Union Checklist. That means the splits I blogged about recently are now official.

Besides the high-profile splits of Winter Wren, Whip-poor-will, and Black Scoter, the checklist committee also did some major rearranging of scientific names, splitting a number of genera and reassigning several species to a new genus. They do this whenever scientific studies (usually DNA studies these days) make it clear that birds currently classified in the same genus are not, in fact, each other’s closest relatives. Although most such splits this time around were based on DNA evidence, vocalizations also support most splits. Below we’ll take a quick survey of what’s changed and how audio was involved.

Species split

Winter Wren is split into three species: Pacific Wren (Troglodytes pacificus) in northwestern North America; Winter Wren (Troglodytes hiemalis) in eastern North America; and Eurasian Wren (Troglodytes troglodytes) in the Old World. Vocal differences were important in this split; see my older posts on how to separate Pacific from Winter Wrens by song and call.
Whip-poor-will is split into Mexican Whip-poor-will (Caprimulgus arizonae) and Eastern Whip-poor-will (Caprimulgus vociferus). Vocal differences were important here as well; see my earlier post on this topic.
Black Scoter is split into Black Scoter (Melanitta americana) in the New World and Common Scoter (Melanitta nigra) in the Old World. Once again vocal differences were key, and once again you can hear them in an earlier post.

A couple of Latin American trogon species, the Greater Antillean Oriole, and the Elepaio of the Hawaiian islands were also split.

Changes in Genus

“Brown” Towhees Move to Melozone

Abert’s, Canyon, California, and White-throated Towhees will move from the genus Pipilo to Melozone, where they will join the Rusty-crowned, White-eared, and Prevost’s Ground-Sparrows. This genus split makes sense when you listen to the songs: the “brown” towhees sing with unmusical high-pitched trills and squeals that are very different from the rich, musical series of the “true” towhees.

“True” Towhees Remain in Pipilo

These species usually sing songs composed of 2-4 series of fairly musical notes — sometimes highly musical notes. Some of them can be confused with each other, but rarely would they be confused with any of the “brown” towhee songs.

“Nashville” Warbler complex moves to Oreothlypis

Nashville, Virginia’s, Lucy’s, and Colima Warblers will move to the new genus Oreothlypis, along with the Orange-crowned and Tennessee Warblers. This group is characterized by songs that are composed of 1-3 rapid (but not buzzy) trills. The similarities are obvious on the spectrograms and to the ear:

Blue-winged and Golden-winged Warblers remain in Vermivora

These two species, plus their extinct relative the Bachman’s Warbler, remain in Vermivora. All three are linked vocally by their very buzzy songs, quite similar to one another but quite different from those of the species leaving the genus.

Bachman’s Warbler songs can be heard at the Macaulay Library: [1 2]

Crescent-chested and Flame-throated Warblers move to Oreothlypis

This is one change that doesn’t seem to be supported by vocalizations. These two Central American species were formerly in the genus Parula with (surprise) the parulas. And their songs sound very like those species — high and buzzy — not at all like the songs of the other bird moved to Oreothlypis.

These embedded iframes are great, but they take up a lot of space, so we’ll continue on this theme tomorrow.

<iframe src=”http://www.xeno-canto.org/embed.php?XC=21740&simple=0″ scrolling=no frameborder=0 width=340 height=230></iframe>

AOU Checklist News!

26 March 2010 Nathan Pieplow

The North American Checklist Committee of the American Ornithologists’ Union has published the results of its deliberations on the first round of proposed changes from 2009, and it has updated the slate of proposals currently under consideration. Here’s a quick summary of the changes that affect species splits north of Mexico. (I won’t get into all the changes to scientific names, even though those topics are just as interesting in my opinion — you can click through to read about those yourself.)

Proposal accepted

This split will become official once the next checklist supplement is published in the July 2010 issue of the Auk.

Split Pacific Wren from Winter Wren. As I reported earlier, this split did indeed pass, and unanimously at that. However, note that the names “Pacific Wren” and “Winter Wren” are not final. The committee is considering an addendum to the proposal that would split eastern North American birds from Eurasian birds and change the names of the American species to “Western Winter-Wren” and “Eastern Winter-Wren.” Stay tuned.

Proposals rejected

In most cases, a 2/3 vote of the committee is required for a proposal to pass. These proposals failed to muster that level of support:

South Hills Crossbill. The proposal to split South Hills Crossbill (Type 9) from Red Crossbill failed on a vote of 6 “yes” votes to 5 “no” votes, with three of the “no” voters indicating that they would be open to changing their minds if presented with more data. Two of those voters preferred to deal with the North American Red Crossbill complex as a whole, rather than splitting one type at a time, piecemeal. Thus, most of the committee appears to accept that the different call types of Red Crossbill are likely good species, but I think it may be a while before those species appear in your field guide.
The split of Western Scrub-Jay. The proposal to split the interior “Woodhouse’s” Scrub-Jay (woodhousei) from “California” Scrub-Jay (nominate californica) failed on a vote of 7 “yes” votes to 5 “no” votes. Many members of the committee felt that more data were needed from contact zones. The tagalong proposal to split the southern Mexican subspecies sumichrasti into yet a third species gained even less committee support. Vocal differences between woodhousei and californica have been reported, and you can expect those differences to be discussed in a future post on this blog.

New proposals

The checklist committee never sleeps. The following splits of North American species are now under consideration:

Split Black Scoter (Melanitta americana) from Common Scoter (Melanitta nigra). I wrote about this split recently. This proposal was originally submitted in 2006 and failed to pass at that time, but the recent publication of Sangster (2009) has revived it. Personally, I think it’s a clear-cut split, but we’ll see if the committee agrees.
Split Curve-billed Thrasher (Toxostoma curvirostre) into two species: the western palmeri group and eastern curvirostre group. The proposal makes no recommendation regarding the resulting English names. The proposal cites various genetic data, which I won’t comment on, but it also cites vocal differences, including differences in calls. I’m a little skeptical of these differences, but I’ll investigate them in the future and report back on what I find.
Split Whip-poor-will (Caprimulgus vociferus) into a nominate eastern species and the southwestern arizonae species, on the basis of subtle but easily diagnosable differences in song, differences in egg coloration, and (most importantly) a hot-off-the-presses study demonstrating that the vociferus and arizonae groups may be as genetically distinct from one another as either is from the Dusky Nightjar (C. saturatus) of Costa Rica and Panama. I haven’t been able to track down the article text yet, so I can’t say what I think of it.

As you can see, vocal differences are playing an ever-more-prominent role in taxonomic decisions. Look for more on this topic from me in the future.

Pacific Wren’s a Done Deal

7 January 2010 Nathan Pieplow

The grapevine tells me that the AOU checklist committee has voted to split Pacific Wren from Winter Wren. This is fourth-hand information, but it originates with a member of the checklist committee and I believe it’s reliable.

This means the split is a done deal, but it’s not official until the committee publishes its 51st supplement to the checklist, which will happen in July 2010. Between now and then, it would behoove birders, especially those in the Mountain West, to pay very careful attention to any Winter/Pacific wrens they may encounter. Here in Colorado, we still have a lot of work to do to try to figure out the occurrence patterns of the two species, and I bet the same is true in many other states as well. Although there are certainly visual differences, sounds remain a key distinction between these species; see my earlier posts on differentiating them by call and by song.

Meanwhile, if you’re looking for more information on why these two species are being split, check out Nick Sly’s post on the subject from 2008. It’s marvelous.

Pacific Wren, Part Two

15 October 2009 Nathan Pieplow

It was a wet and foggy day in April. I was standing in a damp little nook in dense woods, long before the first leaves would even think about opening, weeks before most migrating birds would get within a thousand miles of southeast South Dakota, listening to a cascade of musical notes that seemed like it would never end. It was echoing off the trees and the mossy banks, coming from somewhere tantalizingly close — but from exactly where, I couldn’t for the life of me figure out. After I stood there for perhaps ten minutes, I finally spotted it: a tiny brown bird singing from a pile of leafless brush, fifteen feet in front of me in plain sight. My first Winter Wren.

By some strange coincidence, the details of that experience almost perfectly match the details of my first encounter with Pacific Wren, when, on another wet and foggy day in April, I spent another ten minutes trying to find the amazing vocalist hidden among the dense, damp vegetation, this time on the slopes of Skinner Butte in Eugene, Oregon. At the time I had little idea I was seeing a different bird than the one I knew from the east. The song was familiar, or so I thought — unmistakable, really.

To this day, in the field, I have some difficulty separating the songs of the two forms (which may be separate species soon, for those of you just tuning in). Both are remarkable vocalists, with long-running musical strings of jumbled high-pitched notes and trills:

Winter Wren song, Hampshire County, Massachusetts, 20 June 2008. Recording by Andrew Spencer.

Pacific Wren song, Humboldt County, California, 28 March 2009.

It’s not as easy as separating them by call, but with practice, Winter and Pacific Wrens are usually distinguishable by song. Here are some points to consider:

First of all, in the above examples, don’t let the shorter Pacific song fool you. Strophe length is variable in both forms, and Pacific’s songs may actually average longer than Winter’s. Pay no attention to duration!
Although I can’t vouch for this across the board, the sample I’ve studied strongly suggests that Pacific Wren tends to sing with more trills given closer together, so that the song is composed of >50% trills, while Winter Wren tends to sing with longer jumbles of individual notes and fewer trills more widely spaced, so that the total song consists of <50% trills.
Tone quality is key. Many people consider the song of Pacific to be “drier,” or, in the words of Sibley, “more mechanical-sounding” and “buzzy” with “hard trills.” The difference is one of musicality. To my ear Pacific’s song sounds higher-pitched, but you’ll note on the spectrograms that the maximum and minimum frequencies of both songs are almost exactly the same. The difference is that Winter Wren shows very little frequency change within individual notes (with the trills usually clustered at the bottom of the song), while almost every one of Pacific Wren’s individual notes sweeps from below 4 kHz to about 8. Thus the difference is roughly equivalent to the difference we saw between the songs of Field Sparrow and Black-chinned Sparrow. The Pacific Wren’s notes, especially its trills, are less musical because they are changing pitch too rapidly. Practically every single one of the Winter Wren’s notes has a bell-like, musical quality, but the Pacific Wren has a much lower percentage of musical notes.

A good way to think of the difference in tone quality is to listen for the trills inside the wren songs and compare them in your head to the the “classic” song of Dark-eyed Junco and the “classic” song of Chipping Sparrow (which are, of course, themselves often difficult to separate by ear). The Winter Wren tends to have the more musical, junco-like trills, while the Pacific Wren often trends towards an unmusical, Chipping Sparrow-like (or even Brewer’s Sparrow-like) lisping rattle.

Song delivery also differs, although this can be difficult to ascertain unless you have a great auditory memory. Winter Wren males have only a few stereotyped songs in their repertoire; successive strophes of song are almost always identical. Pacific Wren males sing with far more songtypes, and they also recombine their songs — the beginning notes of successive strophes are frequently identical, but the endings vary widely.

For more practice, and to hear some more of these fantastic bird songs, head over to Xeno Canto’s Winter/Pacific Wren collection.

Pacific Wren, Part One

9 October 2009 Nathan Pieplow

Pacific Wren, Seattle, Washington. Photo by Tom Talbott (Creative Commons license 2.0).

The American Ornithologists’ Union Checklist Committee recently updated its slate of taxonomic proposals. Lots of exciting stuff here, including proposed species status for our old friend, the South Hills Crossbill, and a split of Western Scrub-Jay. The proposed split I want to focus on today, though, is one that’s long in coming, and quite likely to pass, in my opinion: the split of Winter Wren into eastern and western North American species.

Why split the Winter Wren? For starters, eastern and western populations are 8.8% divergent in their mitochondrial DNA. (Trust me, that’s a lot.) Songs and calls differ diagnosably. Furthermore, the two forms nest side-by-side in the northern Canadian Rockies without interbreeding. Analysis of vocalizations and genetics haven’t turned up anything that really looks like a hybrid. Really, this looks like a pretty straightforward split, even by the “old” biological species criteria.

So, it looks like come next summer, we’ll probably have a new taxonomy in the genus:

Winter Wren, Troglodytes troglodytes: breeding from east-central British Columbia east across Canada and down through the Appalachians; wintering in the eastern United States, mostly east of the Great Plains. It’s highly likely that this species will eventually be split from the Eurasian birds, in which case the scientific name of our Winter Wren would revert to Troglodytes hiemalis, a direct translation of its common name in America (Eurasian birds are usually just called “Wren”).
Pacific Wren, Troglodytes pacificus: breeding in Alaska through the northern Rockies to the Yellowstone area and down the Pacific coastline to Central California; mostly non-migratory, though wandering casually southward in winter. The distinctive Aleutian birds would be included in this species.

How do you tell the two apart by sound? For today, we’ll look at the calls, which is the easiest way to identify them, especially in winter.

Calls

With direct comparison of soundtracks and spectrograms, the differences are obvious. The Winter Wren’s call is much clearer, with discrete harmonic bands; both spectrographically and aurally it is reminiscent of the call of Song Sparrow. The Pacific Wren, by contrast, has a call that is much noisier and higher-pitched, and, on average, slightly briefer. It is often compared to the call of Wilson’s Warbler. Although the call may not look higher-pitched on the spectrogram (since the minimum and maximum frequencies of both calls are about the same), note that the darkest part of the Pacific Wren spectrogram (and therefore the loudest part of the call) tends to concentrate around 6-7 kHz, while the darkest part of the Winter Wren spectrogram comes in at about half that. This accounts for the perceptual difference in pitch.

In my next post I’ll look at how to tell these two species apart by song. As these two are both fantastic singers, it will be a melodious post indeed!

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