South Hills Crossbill

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.

The Crossbill Quiz: Answers

24 September 2009 Nathan Pieplow

Here are the answers to the quiz from the last post:

a. Type 4

Type 4 is believed to specialize on the cones of Douglas-fir. It is widespread but somewhat irregular in its distribution: it is usually common in moist forests of the Pacific Northwest and can be frequently found in dry forests there also. It is regular in southeast Arizona, and indeed this particular recording was made at Barfoot Junction in the Chiricahuas in May 2009. It appear to be absent some years from Colorado, but fairly common in other years; 2009 saw a decent influx of this type into the state.

Ken Irwin (unpubl.) has proposed that hidden inside Type 4 there is another call type, Type 10, that specializes on sitka spruce in coastal California. It’s still unclear to me whether Type 10 is a separate call type or just a variation on Type 4. Whatever the case, Type 10 seems to wander widely, at least across the northern states, out to New England and Maryland.

The Type 4/10 group, as a whole, sounds very distinctive because of its upslurred calls. It may be a little hard to hear that they are upslurred because they are delivered so fast, but the rising, flicking quality of the calls is pretty distinctive, reminding some people of the “whit” calls of Empidonax flycatchers.

b. Type 9, the South Hills Crossbill

This type is sedentary and restricted to the South Hills and Albion Mountains of Idaho, where it feeds on the local variety of lodgepole pine. It sounds kind of like Type 2, clear, simple, and downslurred, but it is noticeably low-pitched. I think it is kind of “dull-sounding,” without much ring or resonance, but I’d be interested to hear how other people describe the difference. I recorded this in the South Hills in September 2009.

c. Type 2

Here’s a Type 2. This is probably the most numerous crossbill in North America; it is common almost everywhere Red Crossbills can be found. It is surmised to specialize on ponderosa pines. Across its range its calls are variable, but the high-pitched, clear, downslurred quality is fairly distinctive. This recording was made in Boulder County, Colorado, in July 2007.

d. Type 3

This is one of the smallest crossbills (only Irwin’s proposed Type 10 is similarly small) and is one of the most common crossbill types in moist northwestern forests, apparently specializing on western hemlock. It also can be found across the boreal forest, occasionally into New England, and it wanders rarely into the southern Rockies — there are now two certain records for Colorado and more in the “probable” category. There are also recordings from Arizona.

Types 3 and 5 sound similar to my ear: they are more complex than the types we heard above, less clear and less obviously upslurred or downslurred. Type 3 is the duller-sounding of the two, but I must admit I need practice with this identification. This particular recording, the second-ever for Colorado (from the Grand Mesa, February 2009), was made by Andrew Spencer when I was right beside him–and I didn’t turn on my microphone because I thought they were “just” Type 5s. To be fair, Andrew recorded them because he thought they were White-winged Crossbills. 🙂 He didn’t identify them until days later when he looked at the spectrogram.

e. Type 5

This is the “other” common crossbill in Colorado (besides Type 2), a widespread bird of high elevations in the West, apparently adapted to feed on lodgepole pine but also very fond of Engelmann spruce. In direct comparison I think it sounds more “metallic” than Type 3, but it’s a tough call in the field. A distant flock can sound a lot like a bunch of crickets. This recording was made in Larimer County, Colorado, in June 2009.

The Crossbill Quiz

19 September 2009 Nathan Pieplow

Last week I facilitated the Sound Identification Panel at the Western Field Ornithologists Conference, which is a wonderful privilege I have been treated to for each of the last four years. For those who don’t know, the Sound ID Panel is an annual WFO tradition started by Sylvia Gallagher. In front of a large live audience, a moderator (that’s me) quizzes an expert panel on the identification of mystery bird sounds. This year our panelists were Ted Floyd, Oscar Johnson, Jon Feenstra, Rich Hoyer, and Tayler Brooks, and I must say they did an outstanding job. In collaboration with each other, and notwithstanding the occasional wrong answer, they managed to identify almost every mystery sound in the end, and believe me, that’s not an easy feat.

In 2009 I decided to cross a line I’ve been reluctant to cross in the past. I put Red Crossbills in the mix. It seemed natural, since the conference was in Idaho, home to the endemic South Hills Crossbill, and our keynote speaker was crossbill guru Craig Benkman. I gave the panel the following quiz:

Red Crossbill Call Types: Matching

In this quiz you’ll hear one example of each of the four most common and widespread crossbill types in the western United States, listed below with the tree species they are believed to specialize on:

Type 2 (Ponderosa Pine)
Type 3 (Western Hemlock)
Type 4 (Douglas-Fir)
Type 5 (Lodgepole Pine, Rocky Mountain variety)

Plus, given the location of the conference, we’re tossing in the sedentary and range-restricted South Hills Crossbill, endemic to Idaho, which has been proposed as a separate species, Loxia sinesciuris: