A friend loaned me a copy of the most recent Washington Birds and
gave me chance to look over the description of the hummingbird
identified by the authors as Allen's x Rufous. I thought there
might be some interest in a study I did in 1990 on back color
in Rufous Hummingbirds.

In that study, which was subsequently published in Oregon Birds
(16(3):218-222), I found that most Rufous Hummingbirds show some
amount of green. I divided the back into quadrants and assayed
the amount of green in each sector. The sectors where then
averaged. Of the 37 males captured, only 16% showed no green.
52.7% showed between 1 and 25% green on the back. 27.8% showed
26 to 50% green (almost certainly discernible in the field) and
one bird had nearly 70% green on the back. All birds fell well
within the expected measurement range for Rufous Hummingbirds.

M. Ralph Browning of the National Museum of Natural History
checked his collection and reported the following to me:

"...I checked our collection of _S.rufus_ for green-backed
'adults.' I found a few, including a couple with backs that would
fall into category 3(51-75%). My general impression was that we
have more green-backed birds from the Pacific Northwest and Alaska
than from elsewhere in the breeding range of _rufus_."

There is evidence to suggest (though a lot more work needs to be
done), that green-backed birds are first alternate males.

I believe the bird in the photo in WB is one of these green-backed
male _rufus_. This judgment is based upon the deeply notched
2nd rectrices which show up well in the photo. There have only
been one or two credible _sasin_ x _rufus_ records each
describes reduced or absent 2nd rectrix notching. The description
of the display flight is not particularly "Allen-like". For a
good comparison of _Selasphorus_ displays see Tyrrell's
_Hummingbirds: Their Life and Behavior_. This book also has some
amazing photos of both Allen's and Rufous that you can quite
literally see to bird lice on.

I do have a few photocopies of my report from _Oregon Birds_.
Anyone interested can send me their address and I will send them
a copy while supplies last.


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* Mike Patterson, Astoria, OR * God abhors a naked singularity
* mpatters at ednet1.osl.or.gov * S.Hawking
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