Blue-headed and Mountain Vireos

Jlstasz (Jlstasz@aol.com)
Sun, 5 Apr 1998 08:24:24 EDT 

Hi Folks!

As many of you know, the Solitary Vireo complex was split into Blue-headed
Vireo [in the East], Plumbeous Vireo [in the West], and Casin's Vireo [in the
northwest]. The National Geographic Field Guide and a recent article in
Birding magazine cover these nicely.

What many do not know is that there are two subspecies of Solitary Vireos
described from the East...both are now call Blue-headed Vireo. The source most
will have is Arthur Cleveland Bent's "Life Histories of North American
Wagtails, Shrikes, Vireos, and their allies" . The Blue-headed Vireo (Vireo
solitarius solitarius) is supposedly only a migrant through Maryland. The
Mountain Vireo (Vireo solitarius alticola) is supposedly the breeding form.
Compared to Blue-headed Vireo, Mountain Vireo is slightly larger, has a grayer
back, and reportedly has a sightly different song. Mountain Vireo breeds in
Appalachians [and Piedmont?] north to about Pennsylvania. Blue-headed Vireo
breeds from Pennsylvania north. 

Because most birders have been unaware of the differences, few have kept field
notes with the detail to help solve some questions.

(1) Are the two forms really separate? Plumage? Song? Call note?
(2) Do the two forms have different migration routes?
(3) Is there a difference in timing of migration?
(4) What are the real limits of the breeding ranges?

I would ask that you take up the challenge this Spring and spend a little
extra time looking at and listening to Blue-headed Vireos. Can you keep track
of the birds you find and note them as:

(1) Blue-headed Vireo [subspecies uncertain]
(2) Blue-headed Vireo (Vireo solitarius solitarius) [the smaller green-backed
migrant]
(3) Mountain Vireo (Vireo solitarius alticola) [the larger grayer-backed
breeder]

In Maryland, the earliest spring arrival date is March 22. Peak migration is
from about April 20 to about May 5. The earliest egg date is June 1, and the
latest egg date is June 29. 

Good Birding!

Jim Stasz
North Beach MD
jlstasz@aol.com