Monday, January 24, 2011

Proposed split: Gambel's and Bailey's Chickadees

Mountain ChickadeeProposed Gambel's Chickadee, spp. grinnelli, King Mountain, Harney Co., Oregon, 26 May 2009 by Greg Gillson.

 

There is a recent proposal before the A.O.U. (American Ornithologists' Union, Committee on Classification and Nomenclature, North & Middle America) to split Mountain Chickadee, Poecile gambeli into two species. The new species would tentatively be called Gambel's Chickadee Poecile gambeli and Bailey's Chickadee Poecile baileyae.

Both of these forms of Mountain Chickadees are common in the Pacific Northwest.

As is the case for several recent splits of North American birds (Winter and Pacific Wren is a recent example), published research showing differences in songs and calls, together with supporting DNA evidence, were the primary deciding factors for recommending separation. They don't really look that much different.

Not all recommendations to the committee are passed. But if accepted, the A.O.U. could update its checklist in July 2011, making this split official.

Mountain Chickadees are found from the Rocky Mountains westward in drier pine forests to timberline.

The proposed Gambel’s Chickadee is found in the Great Basin and Rocky Mountains. In the Pacific NW it is found in mountain forests and juniper woodlands in interior British Columbia, northern Idaho, SE Washington, and NE Oregon (to the Ochoco Mountains in north central Oregon).

The proposed Bailey’s Chickadee is found in coastal California, Sierra Nevada, and the Cascades of Oregon and Washington. In the Pacific NW it is found in the Klamath Mountains of SW Oregon and northward primarily on the east slope of the Cascades to Mt. Rainier but, apparently, not in British Columbia (Birds of Canada. 1979. Godfrey).

There may be some areas in the Pacific NW where the two forms come together.

In the field, the primary separation of these forms is range (they are non-migratory) and breeding song. In-hand measurements can be used to identify captured birds or specimens. On average Gambel's is tinged buffier below with a wider white eyestripe and perhaps more white on the lores. But a comparison of the two photos here shows how difficult this identification would be based only on plumage. Both the Sibley and the National Geographic guides illustrate the two forms of Mountain Chickadees.

Gambel's Chickadee reportedly has a wider range of pitch between song notes than Bailey's Chickadee. If this split goes forward birders will need to really listen to the songs. Listen to Mountain Chickadee songs.

 

Mountain ChickadeeProposed Bailey's Chickadee, spp. abbreviatus, Sunriver, Deschutes Co., Oregon, 3 February 2008 by Greg Gillson.

 

4 comments:

  1. A dissenting view of this split--at least for vocalizations--is this recent post presented on EarBirding.com:
    http://earbirding.com/blog/archives/2675"

    ReplyDelete
  2. Your two photos show quite a bit of difference in extent of the black bib onto the chest. Is this consistent? or age- or sex-related? Might be worth checking to see if this is useful.

    Wayne Hoffman

    ReplyDelete
  3. Just an update. The AOU did not accept this split at their last meeting. It could come up again for consideration if more research brings to light further differences.

    ReplyDelete
  4. I have a tree full of these adorable little birds.

    ReplyDelete