Hi all,

Even after listening to my recording from yesterday morning again
(with headphones, and while viewing the spectrogram using the software
Audacity) and browsing recordings of Barn Owl, Great Horned Owl and
others on the web and in Bill Evans "Night Flight Calls" CD, I went to
bed last night still strongly leaning towards this being a recording
of a Barn Owl (same recording posted yesterday):

    http://soundcloud.com/paul-j-hurtado/battelle-darby-owl-14aug2012
    (Might need headphones and a loud volume to hear all 5 renderings
of the call)

The screech calls given by Great Horned Owls just didn't seem to fit
what I'd heard.  Still, not hearing much in the way of confirmation of
my ID, I wanted to be sure. So I woke up early today and slipped out
of the house with better recording gear and headed to Battelle Darby.

When I arrived, the birds were calling. From a distance, the
recordings sound as above, the call was mostly a narrow band just
above 2kHz with a slight downslur towards the end. After getting some
decent recordings, I decided to walk the trail to get closer to the
still distant birds.

A few hundred yards later, I was recording a vocalizing Great Horned
Owl from somewhere in a trailside Cottonwood Tree. The bird then flew
down to the trail (where I could confirm the ID as Great Horned, not
Barn) and called a bit more before flying off towards the west
(towards the riparian woodlands along the creek).  Definitely not a
Barn Owl! (David Tan had reported Barn Owls here earlier this summer,
including visual confirmation on at least 1 occasion.)

Here's the best clip from this morning's visually confirmed GH Owl,
recorded at about 75-150yds. The first version is closer to the raw
recording, the second sounds better (though still a bit quiet):

   http://soundcloud.com/paul-j-hurtado/great-horned-owl-15aug2012
   (high pass filter only, WAV format)

   http://www.xeno-canto.org/107584
   (high pass filter plus noise reduction using Audacity, MP3 format)

Sound traveling over large distances (especially horizontally through
vegetation) can be "filtered" and in this case it appears what I had
heard was a fairly typical
Great Horned Owl vocalization, but the distance left me hearing (and
initially, recording) just the lower frequency components of the
calls, which lead to my initial confusion.

A few lessons learned:
1. My recording gear should be mandatory birding gear whenever I leave
my house before dawn!
2. Unless an audio ID is spot-on typical and obvious, be very
cautious! Especially in late summer when young birds are vocalizing.
3. Spectrograms are incredibly useful but can be misleading and should
always supplement, not replace, what we hear in recordings.

Good birding,
Paul Hurtado

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