Browsed by
Tag: Common Scoter

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.

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.