Subject: [Tweeters] barred owls
Date: Apr 8 15:21:27 2011
From: rrpearson at centurytel.net - rrpearson at centurytel.net


On Apr 7, 2011, at 1:20 PM, owler at sounddsl.com wrote:

> Males are smaller than females, as is true with most raptors, though he
> will have the deeper, lower pitched call when the two are dueting.

On Apr 7, 2011, at 16:32, kevinpurcell at pobox.com wrote:

>The female has a pronounced vibrato to the call. It's easy to tell if you
>hear them calling back and forth. Once recognized it's not easily
>forgotten.

On the whole, these are both correct. However, a male with a high-pitched
voice can overlap in voice range with a female with a low-pitched voice. So
if you have a single owl, even recorded and analyzed, the pitch of the voice
may not be enough in itself to have a positive ID if it is in the middle
range for Barred Owls. All the paired owls I have recorded, however, do have
a definite, often broad, distinction in voice pitch with the male lower in
pitch, so this is probably a good general rule for pairs. (But this does not
rule out the possibility of having a pair with similarly-pitched male/female
voices). Local acoustic conditions can also affect the perceived pitch of an
owl's voice.

Both the male and female can have a vibrato ending to their calls; the
female more consistently so. The female vibrato tends to be more drawn out
and holds the initial note longer, at a consistent pitch, before descending
in pitch with the vibrato. Over the years, this has become the
distinguishing feature for me to determine sex, rather than pitch of voice
or vibrato: female "hoooooo-aaawwwww", male "hoo-aawwww."

Two males, during a vocal border conflict, will often both include a heavy
vibrato to the last notes of their calls, and there is often a distinct
difference in the pitch of their voices, although generally closer in pitch
than a male/female pair. The lack of a female-type vibrato note as well as
behavioral differences from paired owls interacting indicates two males
rather than a pair in these instances.

Another distinguishing feature to their simultaneous calling (I reserve
"duet" for true antiphonal episodes) is that most often the male will
continue calling once the intensive interaction is completed, most often
with a rising series call (each note ascending slightly in pitch):
"hoo-hoo-hoo-hoo-hoo-hooo-aawww." Sometimes the female will also continue,
most often with a 1-note call. Over 20 years, I've never heard the reverse
(female rising series/male 1-note).

While there appears to be some triggering, where the sound of one owl's
voice instigates the call of the mate, especially to begin, this is not a
consistent element once a simultaneous calling bout has begun. Once started
and excited, each owl appears to go at its own pace, sometimes overlapping
calls, sometimes one then the other. During the cool-down period after the
intensive interaction, if both owls continue to call periodically, there
appears on the surface to be a male/female/male/female pattern, but, again,
this seems to be individual pacing rather than a call-dependent duet, as
sometimes the calls overlap and sometimes one owl will call twice before the
second owl calls again. Whenever mated adults call simultaneously, there
appears to be a combination of voice-triggered as well as individually-paced
calling, rather than a structured "duet" as some birds exhibit. (However, I
many times use "duet" because it is much easier than typing out
"simultaneous calling." On the same note, "song" probably should be used for
Barred Owl vocalizations rather than "call.")

(Above based on analysis of several hundred field-recorded Barred Owls over
10 years).

Bob Pearson
Packwood, WA