Fred Sharpe poses the following question:

> Concerning townsend-hermit hybridization:
>
> If an observer is conducting point censuses or collecting
presence/absence
> data (by hiking through appropriate habitat) is it possible for them to
> gather ANY data that can provide insight into the HETO question?
>
> Presumably an experienced observer can separate Townsends form hermits
> outside the hybrid zone. Therefor could an increase in call variation
alert
> the observer that they have entered into a hybrid zone.? The big
question
> is: to what extent does call characteristics reflect the degree or
> directionally of hybridization? Are their any trends, or rules of thumb
> that an observer could be vigilant for within the hybrid zone?
>
> I ask because many observers collect a variety of biological data while
in
> the field (and are following ridged survey protocols), and don't have the
> luxury getting a visual on every dendroica (particularly those up in the
> top of 200 foot Doug firs)
>
> Just wondering.....

While in Texas in April I heard a male Black-throated Green Warbler giving
its chip note, which, to my ear, was identical to that of a Townsend's
Warbler. By my side was Michael O'Brien, who has a superb ear for
separating calling warblers (especially migrants overhead in the dark). We
then briefly discussed chip notes of Townsend's/Hermit/Black-throated Green
Warblers. He seemed to think the call note of these three warblers were all
very similar. I got the feeling he would be reluctant to bet on an
identification without visual confirmation. Dunn and Garrett's Peterson
Field Guide to the Warblers states they are all very similar also, but does
note Townsend's is slightly higher.

With the above in mind, I would be hesitant to place much faith in data
for this species pair based solely on call notes, especially from calling
birds 200' up in a fir forest. Rohwer and Wood discuss characteristics of
hybrids in the zone in question at length in their recent paper in the Auk
(115:284-310. 1998). Eight characters (color and patterns of mid flank,
lower flank, bib corner, face, extent of yellow, intensity of yellow,
crown, and back color) are used in their study to delineate the hybrid
zone. Theirs is a marvelous study employing methods that are very difficult
to assess accurately in the field.

It would be much too convenient if the call notes of Townsend's/Hermit
Warblers were easy to discern.

Andy Stepniewski
Wapato WA

Andy Stepniewski
Wapato WA