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Fwd: NC Pacific-slope Flycatcher



More interesting stuff. Good stuff, in this case!

--
Harry E. LeGrand, Jr.
N.C. Natural Heritage Program
Division of Parks and Recreation
1615 MSC
Raleigh, NC 27699-1615

Office: (919) 715-8687
Home: (919) 832-3202
FAX: (919) 715-3085
e-mail: harry.legrand@ncmail.net
http://ils.unc.edu/parkproject/nhp/index.html

------- Forwarded Message Follows -------
Date:         Thu, 27 Jan 2000 20:05:10 EST
Sender: NBHC ID-FRONTIERS Frontiers of Field Identification
              <BIRDWG01@LISTSERV.ARIZONA.EDU>
From: Tony Leukering <GreatGrayO@AOL.COM>
Subject:      Re: [BIRDWG01] NC Pacific-slope Flycatcher

Hi all:

I have been sitting on this discussion but am impelled to post on it, due to
Larry Gorbet's post.  While, I have almost no experience with calling
Pacific-slope Flycatchers (PSFL) or those annoying 'tweeners of the northern
Sierras and the Cascades, I mainly wish to expound on the likelihood of
"Western" Flycatchers (WEFL) in the east.

Ever since my arrival at Colorado Bird Observatory in fall '94, I have been
insisting that we identify every migrant WEFL as WEFL, not as COFL.  While I
believe that a goodly number of the migrants we see and catch are probably
COFLs, there are absolutely NO data that can confirm that.  No one out here
has really looked at the problem.

While understanding that different species of birds are different and that it
can be dangerous to generalize across taxa, I here plan on doing just that.
I believe that the "Solitary" Vireo complex provides at least marginal
argument that PSFLs could be migrating through the Rocky Mountains,
particularly in fall.  My fall banding station at Barr Lake sits only 30
miles east of the foothills out on the plains.  That means that it is only 30
miles from breeding Plumbeous Vireos (PLVI).  Despite that short distance,
Cassin's Vireo (CAVI) greatly outnumbers PLVI at my banding station.  In
spring, the situation is reversed.

The two Pacific-slope species (CAVI and PSFL) have fairly-similar breeding
and wintering ranges and the two Rocky Mountain "species" also have similar
breeding and wintering areas.  Of the two vireos, only CAVI has been
documented as occurring on the east coast.  The female WEFL caught on Long
Island, NY, in fall 1995 measured out to be a PSFL (if I remember that
correctly).

I suggest that PLVI migrates through the mountains, but that non-conducive
weather conditions (read, "snow") typical of the Colorado mountains in spring
may be the cause of many spilling out onto the plains in that season.  Fall
is generally rather clement in CO and the birds are able to migrate south in
the mountains, thus taking the shorter route.  CAVI is an uncommon migrant in
CO in fall, being quite rare in spring.  Since I have only caught immatures
of this species in CO, I suggest that either the stupid youngsters that wind
up in the Rocky Mountains during fall migration either don't make it or they
"learn" that they're supposed to be further west, thus producing very small
numbers in the state in spring.

In general:
    1)  Species breeding on the Pacific slope and wintering in Mexico or
anywhere further south are required to head SE; species breeding in the Rocky
Mountains and wintering in Mexico or further south head S.
    2)  Species breeding on the Pacific slope generally have breeding
distributions extending well into Canada, often to panhandle Alaska whereas
those species that are typical of the drier forests of the Rocky Mountains
generally breed only as far north as Montana.

This combination of factors possibly favors long-distance displacement of
Pacific-slope taxa to the east as compared to that in Rocky Mountain species.
 As further support, many common breeding species that are restricted as
breeders in CO to the Rocky Mountain cordillera are rare or accidental more
than some 20 miles off the mountains in CO, e.g. Red-naped Sapsucker, Western
Bluebird, and Lesser Goldfinch.

Getting back to the main point, I would suggest that if WEFLs are at all like
the vireos, PSFL would be the more likely of the two "species" on the east
coast.

Tony Leukering
Brighton, CO