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AOU Checklist News!

AOU Checklist News!

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.

Evening Grosbeak Call Types

Evening Grosbeak Call Types

Evening Grosbeak, Soda Springs, CA, 8/3/2009. Photo by C.V. Vick (Creative Commons 2.0).
Evening Grosbeak, Soda Springs, CA, 8/3/2009. Photo by C.V. Vick (Creative Commons 2.0).

In 2004, a paper appeared in the Condor by Kendra Sewall, Rodd Kelsey and Tom Hahn that described several different variants of flight calls in the Evening Grosbeak.  Their fascinating research immediately reminded many of the work on the call types of Red Crossbill, and I heard a few people worry out loud about whether a split of Evening Grosbeak might be in the works.

But there’s no cause for worry.  The “call types” of Evening Grosbeak are not as scary as the call types of Red Crossbill.  While Red Crossbills sort into at least 10 call types in North America, Evening Grosbeaks apparently sort into just 5.  And while multiple Red Crossbill call types often occur in one area (which is part of the justification for splitting them into separate species), the Evening Grosbeak call types usually stay in fairly well-defined, separate geographic ranges.  In fact, Sewall et al. note that the five call type groups seem to match the five subspecies groups in a decades-old taxonomy.

Learning to identify Evening Grosbeak call types is a fascinating exercise, especially if you come upon a wandering flock and want to know where they likely originated.  This post aims to provide an introduction to the different “types” and how to tell them apart.

“Flight calls” vs. “Trills”

The terminology used by Sewall et al. (2004) as well as the BNA account of Evening Grosbeak distinguishes two main calls that are typically heard from the species: “flight calls” and “trills.”  Neither source mentions how the “trills” may vary among groups; this post is going to concern itself solely with the flight calls, which are the most common vocalizations.

Type 1

Range: The northern Rockies and the Cascades, from at least British Columbia south to Oregon, northern Wyoming, and the Black Hills of South Dakota.  Wanders to the northern Sierra Nevada and to Colorado.

Flight call:

Evening Grosbeak Type 1 flight calls, Whitewood, SD.
Evening Grosbeak Type 1 flight calls, Whitewood, SD, 11/20/2007.

Even though the spectrogram shows that it tends to start at a higher frequency than other types, Type 1 sounds relatively low-pitched, especially compared to Types 2 and 4.  It  has a very clear sound that is distinctive once you learn it.  More than the other types, this one reminds me of a particular Pine Siskin call (but beware!  Pine Siskins can mimic other Evening Grosbeak types in their songs).  Here’s another good recording of Type 1.

Type 2

Range: The Sierra Nevada of California; wanders at least occasionally north to southern Washington.

Flight call:

Evening Grosbeak Type 2 flight calls, California.
Evening Grosbeak Type 2 flight calls, Sierra County, CA, 6/14/2004 and 6/16/2004.

To my ear, this sounds like the clearest, most purely whistled type, even clearer than Type 1, but it is distinctly higher-pitched and more piercing than Type 1.  Type 2 is quite similar to Type 4 and the two may be difficult to distinguish by ear in the field (see below).

Type 3

Range: Boreal forests of Canada east of the Rockies and in the northeastern United States.  Wanders south throughout the East.

Flight call:

Evening Grosbeak Type 3 flight call, Canada. Recording by Chris Parrish on Xeno-Canto (click for link).
Evening Grosbeak Type 3 flight call, Sanguenay, Quebec, 5/21/2007. Recording by Chris Parrish on Xeno-Canto (click for link).

The distinctive Type 3 differs from Types 1, 2, and 4 by being slightly longer and lower-pitched and distinctly burry.  Field guides with an eastern focus have often compared the calls of Evening Grosbeak to certain vocalizations of House Sparrow, and Type 3 is the reason why.

Type 4

Range: The southern Rockies (Colorado and New Mexico), occasionally wandering north at least to the vicinity of Jackson Hole, Wyoming.

Flight call:

Evening Grosbeak Type 4 flight calls, Colorado.
Evening Grosbeak Type 4 flight calls, Delta County, CO, 3/9/2008.

The high-pitched and piercing Type 4 flight calls are most similar to Type 2 flight calls, both on the spectrogram and to the ear, but slighty huskier and less clear.  I’m not certain I could tell them apart in the field with confidence, but the two have never yet been recorded in each others’ range to my knowledge.  Here’s another recording of Type 4.

Type 5

Range: The Sierra Madre of Mexico, north to southeastern Arizona.

Flight call: To my knowledge, only one recording of this type has been made, and here it is:

Evening Grosbeak Type 5 flight call, Arizona. Recording by Rich Hoyer (used here with permission).
Evening Grosbeak Type 5 flight call, Cochise County, AZ, 4/14/1999. Recording by Rich Hoyer (used here with permission).

If this recording is typical, then Type 5 is distinctive: even longer and burrier than Type 3, but high-pitched like Types 2 and 4.  If I had to guess, I’d say that the doubled rhythm is probably due to the whim of this individual bird, not characteristic of Type 5 in general, but who knows? — maybe Type 5 is the Mountain Pygmy-Owl of Evening Grosbeaks.  If you have any recordings of Evening Grosbeak from Arizona or Mexico (or you know someone who does), please let me know!

Regions of Mystery

There are some places where we don’t really know which type to expect:

  • Southwest Oregon and northern California: Types 1 and 2 have both been recorded in this region, and the actual limits of their distribution here are poorly known.
  • Black Hills of South Dakota: The one recording I have is of Type 1, but I think Type 3 might also be likely, and Type 4 might wander in.
  • Arizona: My guess would be that Type 4 is most common in the northern and central parts of the state, while Type 5 is the most likely type to be encountered in the southeastern mountains, but we need more data.

You know what that means: more recordings necessary!

Splitting Scoters

Splitting Scoters

I know, I know — you’re still reeling from the news that Pacific Wren is being split from Winter Wren.  The last thing you’re willing to deal with right now is another taxonomic split based on vocal differences, right?

Somehow, I think you can handle it.

Black Scoter (American form), White Rock, British Columbia, 12/4/2008. Photo by Rick Leche (Creative Commons 2.0).
Black Scoter (American form), White Rock, British Columbia, 12/4/2008. Photo by Rick Leche (Creative Commons 2.0).

In much of the world, this “new” split isn’t even new.  Many authorities, including the British Ornithologists’ Union, have classified Black Scoter and Common Scoter as separate species for some time now, in part on the basis of the striking differences in bill color between males of the two groups: the American and eastern Siberian birds (“Black Scoters”) have an enormous bright orange knob atop the bill, while European males (“Common Scoters”) sport far duller and less decorative schnozzes, making them less conspicuous in flocks of sea ducks — you might consider them the “Stealth” version of the bird.

So far, taking a conservative stance, the American Ornithologists’ Union has continued to recognize only a single species, “Black Scoter,” Melanitta nigra.

Common Scoter (European form), Brouwersdam, Netherlands, 11/15/2007. Photo by Pieter van Veelen. Used by permission.
Common Scoter (European form), Brouwersdam, Netherlands, 11/15/2007. Photo by Pieter van Veelen. Used with permission.

Now comes the best evidence I’ve seen yet that the two should be split.  In a recent issue of the Wilson Journal of Ornithology, George Sangster has published an analysis of the differences in male courtship calls between Black and Common Scoters.  His analysis boils down to this: Black Scoters sound basically alike across their entire range, and the same goes for Common Scoters; but the two forms can always be told apart by the length of their vocalizations (Black’s notes are much longer) and usually by pitch as well (Black’s notes are slightly higher-pitched).

You can hear the differences several places on the web.  Here are some Black Scoter sounds from Manitoba, New Jersey (Cape May and Barnegat Light) and from Chukotka in Russia. Note the plaintive, eerie quality to the calls.

The Common Scoter’s mating call can be heard on this page (which is in Dutch)…not many recordings of this taxon are online, and all the ones I’ve found are truncations of the file I just linked.  The notes of the Common male are less than a quarter as long as those of the male Black, and the overall effect is completely different — nothing at all like those long, haunting whistles from America.  (Note, however, that Black Scoters occasionally make some short notes too…listen to the background of the Barnegat Light recording at 2:35.)

Sangster ends his article with the intriguing possibility that White-winged/Velvet Scoters might also show vocal differences in up to three species groups.  But if you think Black/Common Scoters are hard to find on the web, try looking for the other species!  I’ll give a gold star to anyone who points me towards any (legal) online White-winged Scoter cuts besides this one!

Here’s another beautiful Common Scoter pic:

Common Scoter. Photo by Björn Gudmundsson, used with permission. Clink for link.
Common Scoter. Photo by Björn Gudmundsson, used with permission. Clink for link.
Pacific Wren’s a Done Deal

Pacific Wren’s a Done Deal

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.

White-breasted Nuthatch, Part Three

White-breasted Nuthatch, Part Three

During my research for the last couple of blog posts, I’ve arrived at a surprising conclusion: when it comes to regional variation in calls, few common birds are as poorly understood as the White-breasted Nuthatch, particularly the Rocky Mountain and Pacific populations.

In the first two parts of this series we explored the “quank” calls, which are some of the most common vocalizations of the three populations, and the “fast songs.”  Today we’ll investigate two more types of rapid-fire calls, the “rapid quanks” and the “hit-trills,” and then I’ll leave the subject of nuthatches alone for a little while!

Rapid Quanks

The term “rapid quank” was coined by Ritchison (1983) to describe the long strings of calls that eastern nuthatches would give in high agitation.  The “rapid quanks” are a little tricky to compare among the three populations, because they grade into the regular “quanks,” the “fast songs,” and even the “hit-trills” (see below).  In some ways “rapid quank” is just a catch-all term for agitated calls.

"Pacific" White-breasted Nuthatch rapid quanks, Contra Costa County, CA, 3/26/2009.
"Pacific" White-breasted Nuthatch rapid quanks, Contra Costa County, CA, 3/26/2009.

In my search through all the recordings available to me, the “rapid quanks” of Pacific birds have been the hardest to find.  I suspect this is due to a relatively small sample size rather than a lack of “rapid quanking” by Pacific birds, but I’m not entirely certain of that.  (Note, however, some very excited Pacific birds failing to rapid-quank on this recording.)

Above are some relatively rapid short notes from a bird near its nest in California.  By comparison, the Rocky Mountain birds sound like they’re on speed:

"Rocky Mountain" White-breasted Nuthatch rapid quanks, San Miguel County, CO, 9/3/2006.
"Rocky Mountain" White-breasted Nuthatch rapid quanks, San Miguel County, CO, 9/3/2006.

Especially when they get a little bit upset:

"Rocky Mountain" White-breasted Nuthatch rapid quanks, Clark County, NV, 9/27/2007.
"Rocky Mountain" White-breasted Nuthatch rapid quanks, Clark County, NV, 9/27/2007.

As far as I know, nothing but a “Rocky Mountain” White-breasted Nuthatch ever gives notes at this frantic rate (up to 25-30/sec).  This type of vocalization is highly variable, however, and I particularly recommend checking out a couple of other distinctive recordings of it, here and here (the latter recording, in particular, is repeated so many times in a row that it could be functioning as a kind of song).

When the “Eastern” nuthatches get excited, they’re still much slower, along the lines of the “Pacific” birds:

"Eastern" White-breasted Nuthatch rapid quanks, Lincoln County, SD, 9/1/2007.
"Eastern" White-breasted Nuthatch rapid quanks, Lincoln County, SD, 9/1/2007.

This is about as crazy as they get (in response to an Eastern Screech-Owl tape):

"Eastern" White-breasted Nuthatch rapid quanks, Yuma County, CO, 12/27/2008.
"Eastern" White-breasted Nuthatch rapid quanks, Yuma County, CO, 12/27/2008.

For extra credit, you can listen to more fast-quanking Eastern birds here and here.  Note the tendency to revert to paired notes, the “double quanks” of Ritchison (1983), whenever the bird “catches a breath.”  Again, beware confusion with the diagnostic disyllabic quanks of Rocky Mountain birds.

Hit-trills

Ritchison (1983) didn’t mention a “hit-trill” vocalization, but he did identify a short contact note he called the “hit,” which is frequently extended into a trill, so I figured the name wasn’t much of a stretch.  This is a rather quiet call given in close contact with other nuthatches, and it is very similar in all three populations, although like most of the other calls, it appears to increase in pitch from east to west, and increase in speed in “Rocky Mountain” birds:

"Pacific" White-breasted Nuthatch "hit-trill," Contra Costa County, CA, 3/26/2009.
"Pacific" White-breasted Nuthatch "hit-trill," Contra Costa County, CA, 3/26/2009. Note begging calls of this species also on the cut (at top of spectrogram).
"Rocky Mountain" White-breasted Nuthatch "hit-trill," Larimer County, CO, 6/3/2007.
"Rocky Mountain" White-breasted Nuthatch "hit-trill," Larimer County, CO, 6/3/2007.
"Eastern" White-breasted Nuthatch hit-trill, Monroe County, AR, 3/24/2006. Recording by Randy Little. Macaulay Library #129818.
"Eastern" White-breasted Nuthatch hit-trill, Monroe County, AR, 3/24/2006. Recording by Randy Little. Macaulay Library #129818.

Click here to listen to the above (at 1:15).

White-breasted Nuthatch, Part Two

White-breasted Nuthatch, Part Two

"Rocky Mountain" White-breasted Nuthatch, Madera Canyon, AZ.
"Rocky Mountain" White-breasted Nuthatch, Madera Canyon, AZ, 4/25/2007. Image courtesy Alan D. Wilson, www.naturespicsonline.com

Last time we looked at the most common calls of the three populations of White-breasted Nuthatch.  Here in Colorado, we have both the “Rocky Mountain” and “Eastern” forms of the White-breasted Nuthatch, and I’ve heard a couple of people proclaim that any bird giving a rapid-fire series of calls is a Rocky Mountain individual, while any bird giving a single “yank” note is an Eastern.  Unfortunately, it’s more complicated than that.  All three populations of the species give rapid series of calls from time to time, so the first thing you’ve got to figure out is which type of call you’re listening to.

Since White-breasted Nuthatches have a lot of different call types, it will probably require several posts to discuss them all.  Over the course of this series we’ll mostly follow the terminology of Ritchison (1983) in our discussion of “fast songs,” “slow songs,” “rapid quanks,” and “hit-trills.”  Today’s installment looks at the “fast songs.”

Fast songs

Ritchison distinguished between “slow songs” (which we’ll explore in a later post) and “fast songs.”  Fast songs consist of rapid strings of simple overslurred nasal notes at a rate of about 10 notes/second, and they appear to be similar in all populations of the White-breasted Nuthatch:

"Pacific" White-breasted Nuthatch fast song, Contra Costa County, CA, 3/26/2009.
"Pacific" White-breasted Nuthatch fast song, Contra Costa County, CA, 3/26/2009.
"Rocky Mountain" White-breasted Nuthatch, Larimer County, CO, 6/18/2008.
"Rocky Mountain" White-breasted Nuthatch fast song, Larimer County, CO, 6/18/2008.
"Eastern" White-breasted Nuthatch fast song, Tioga County, NY, 3/16/1991. Recording by Steven Pantle. Macaulay Library #53158.
"Eastern" White-breasted Nuthatch fast song, Tioga County, NY, 3/16/1991. Recording by Steven Pantle. Macaulay Library #53158.

(click here to listen to the above recording at the Macaulay Library)

The length, rate and pitch of fast songs are fairly variable within groups, as far as I can tell, but there appears to be a general trend of increasing pitch as you move from east to west. With more investigation, these differences may turn out to be systematic.

How can you tell when you’re hearing a fast song as opposed to some other vocalization?  Two ways:

  1. Rhythm. Fast songs contain long strings of single notes (not double notes like in the “disyllabic quank” call of Rocky Mountain birds)  in strict rhythm (not accelerating or decelerating).
  2. Behavioral context.  According to BNA, fast songs are given by males hoping to attract a mate; they are often sung loudly many times in a row in late winter and spring. This behavioral context helps differentiate them from some of the “rapid quanks” we will see next, since the two types of vocalizations seem to integrade.

The take-home lesson: long strict series of single nasal notes don’t necessarily identify a bird as a member of the “Rocky Mountain” group.  Double notes in series, though, are a good indicator — see the last post for an example.

More on nuthatches to come.  Stay tuned.

White-breasted Nuthatch, Part One

White-breasted Nuthatch, Part One

Eastern White-breasted Nuthatch, 30 September 2008. Photo by Gary Irwin (Creative Commons 2.0).
Eastern White-breasted Nuthatch, 9/30/2007. Photo by Gary Irwin (Creative Commons 2.0).

Birders have known for a number of years now that White-breasted Nuthatches sort out into three distinct vocal groups in North America — Pacific, Rocky Mountain, and Eastern — following a pattern of three-way separation that mirrors those of several other bird species, including the Solitary Vireo complex (split into Cassin’s, Plumbeous, and Blue-headed) and the sapsuckers (split into Red-breasted, Red-naped, and Yellow-bellied).

However, with the exception of field guides, the ornithological literature has been silent on this point.  Nobody has done a systematic study on the marked regional variation in vocalizations of the White-breasted Nuthatch.  The only in-depth study on vocalizations in the species was done by Gary Ritchison in Minnesota, and so the vocalizations of the Eastern form have been the only ones described in the literature for years; they were the only ones available on commercial bird sound recordings for years too.  Even though the Birds of North America account was revised by its authors in 2008, they made no mention of vocal variation, which seems a shocking oversight.  Spellman & Klicka (2007) published a molecular phylogeny of the species and found evidence for four distinct clades in the species, with boundaries exactly matching those of the vocal groups (except that they found the Rocky Mountain group was divided into two clades, apparently with identical vocalizations).

Thus, since I can’t find this information anywhere else, starting with this post, I’m going to start exploring these vocal differences in some depth.

“Quank,” etc.

Here are the most common calls of the three nuthatch groups.  For simplicity’s sake, we’ll always travel left to right across the country, so you’ll always see Pacific, Rocky Mountain, and Eastern birds in that order.

Pacific White-breasted Nuthach "quank" call, Contra Costa County, CA, 3/26/2009.
Pacific White-breasted Nuthatch "quank" call, Contra Costa County, CA, 3/26/2009.
Rocky Mountain White-breasted Nuthath "disyllabic quank" call, Boulder County, CO, 11/10/2009.
Rocky Mountain White-breasted Nuthatch "disyllabic quank" call, Boulder County, CO, 11/10/2009.
Eastern White-breasted Nuthatch "quank" call, Scott County, MN, 7/6/2009.
Eastern White-breasted Nuthatch "quank" call, Scott County, MN, 7/6/2009.

The first thing you’ll notice is that the Pacific and Eastern birds sound much more similar to one another than they do to the Rocky Mountain birds. Thus begins a theme we will see repeated many times.  Spellman & Klicka found that the Pacific and Eastern birds were sister taxa, separated from one another by the less closely-related birds in the Mountain West.  If this seems surprising, remember that the Solitary Vireo complex follows a similar pattern, with Cassin’s and Blue-headed Vireos looking and sounding more like each other than like Plumbeous.

The calls you see above are variable in each of the groups, so some of the differences you see between Pacific and Eastern in call length and overall inflection may not always apply.  The most consistent difference seems to be one of pitch: the Pacific birds, with their more widely spaced partials, sound a lot higher-pitched than their huskier-voiced, more nasal Eastern cousins.

Identifying the Rocky Mountain birds, meanwhile, seems like a slam-dunk.  Eastern and Pacific birds never make rapid-fire series of call notes, right?  Well, actually, yes they do — several different kinds, in fact.  I’ll be looking at those in my next post!

Pacific Wren, Part Two

Pacific Wren, Part Two

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.
Winter Wren song, Hampshire County, Massachusetts, 20 June 2008. Recording by Andrew Spencer.
Pacific Wren song, Humboldt County, California, 28 March 2009.
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

Pacific Wren, Part One

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

Winter Wren calls, Phillips County, Arkansas, 30 March 2006.
Winter Wren calls, Phillips County, Arkansas, 30 March 2006.
Pacific Wren calls, Humboldt County, California, 28 March 2009.
Pacific Wren calls, Humboldt County, California, 28 March 2009.

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!

Gray Hawk, continued

Gray Hawk, continued

In my last post, I discussed differences in the alarm calls of Gray Hawk (for the purposes of this post, Buteo plagiatus) and Gray-lined Hawk (here, Buteo nitidus — see the last post for taxonomic rationale).  Over the past few days, I have gone through the Gray Hawk sound collection at the Macaulay Library, which has given me some new information.

In my last post I said the alarm calls of Gray and Gray-lined Hawks tend to be “fairly stereotyped within populations.”  In light of what I’ve learned from the larger sample size, I think it’s worth retracting that statement in favor of something like, “the alarm calls of Gray and Gray-lined Hawks are variable within populations, and even within individuals, but are nonetheless consistently separable on several characters.”

Of the characters I mentioned in my last post, the most consistent seems to be energy spectrum; those differences seem consistent across the entire sample size.  Differences in frequency and pattern of inflection are also pretty reliable, although there are anomalous birds here and there.  The differences in duration are tricky, though, since several Gray-lined Hawk vocalizations from Venezuela clock in at around 1.75 sec in length.  It’s clear there is a lot of overlap in this character.

Here are some other ways in which the alarm calls vary:

  1. The noise content of alarm calls in both Gray and Gray-lined Hawk is highly variable.  A clear tone quality (that is, without noise) is the norm in both taxa, but noisy calls are not infrequent, and some birds in both taxa may give noisy and clear calls on the same recording.
  2. Within the context of the constant differences in energy spectrum, phase shifts (period doubling, period tripling, etc.) are common in both taxa, as they seem to be in many species of raptors.

I hope to publish more on Gray Hawks (and other bird sounds) soon, but as I’m in the middle of an unplanned trip, I may not get to it until next week.  Sorry!