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Posted by Bill Pranty on 14:40:16 08/10/07
In Reply to: Bluebird: resident or migrant and 3 questions posted by Paul-the-other
Good afternoon Paul,
There are perhaps eight races of the Eastern Bluebird in the world, of which only two occur in the east. One other reaches extreme southeastern Arizona, while the others occur from Mexico to Nicaraugua.
The southern Florida race grata (occurring from Hillsborough, Polk, Orange, and Brevard counties southward), has been either questioned or rejected by most systematists. Bluebirds with similar-sized bills have been measured in North Carolina and Tennessee. (Stevenson and Anderson [1994] accept the race, but they may not have been aware that Allan Phillips questioned the race in 1991).
Regardless of the validity of grata, determination of this race is by measuring bill length of specimens with calipers -- we're talking a millimeter or two of difference. I'm not aware that grata is a field-identifiable race, with due respects to John B.
As to why southern Florida EABLs may have slightly longer bills, that's difficult to answer, especially given the doubt that grata is a valid race. Maybe the pine seeds south South Florida Slash Pines (variety densa) are slightly larger than North Florida Slash Pines (variety elliottii). Or, maybe is typical variation; most birds that occupy large ranges show minor (and sometimes major) anatomical, vocal, or plumage differences (consider how diiferent humans look and sound across the world).
Finally, I haven't read any paper about the bluebirds reintroduced into ENP, but I remember reading that the Brown-headed Nuthatches reintroducd into the park came from birds captured at Big Cypress National Preserve. Presuming that the bluebirds also came from a local source -- and I'd be surprised if they weren't -- then your final question can't be asked, since all the birds you asked about would be referring to grata.
Best regards,
Bill Pranty
Bayonet Point, Florida
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