Hi Mark (& all),
Great Horned Owls tend to consume Barn Owls when they kill them,
especially during nesting season. ODFW staff at E.E. Wilson Wildlife
Area mentioned to me some years back that they'd often find Barn Owl
feathers, beaks and talons under the Great Horned Owl nests. Last year I
found the same kind of remnants under a roost that was being used by a
Barred Owl. It's getting tough for Barn Owls out there.
So if the Barn Owl carcass was intact, I'd tend to suspect some other
cause.
A couple of other ideas:
1) Since female Barn Owls could be nesting now, you might check for
signs of an egg blockage (bulge in oviduct area).
2) Does the owl seem emaciated? You might try weighing the carcass if
you have a suitable scale.
In the mid-Willamette Valley, some local raptor watchers have commented
on what seems to be a scarcity of voles, partly due to the ongoing shift
of the farming industry away from perennial grass-seed crops, and partly
due to the normal boom-bust population that voles go through. The
gray-tailed vole population peaked in the last couple of winters, and
apparently when they reach a certain density, they become prone to
disease epidemics (plus some farmers will resort to rodenticides).
I've heard reports of Red-tailed Hawks and even Red-shouldered Hawks
that were eating worms out in the middle of fields, possibly a sign of
difficulty finding their main prey. Barn Owls might also be having a
tough time if vole numbers are down.
3) Speaking of rodenticides, one other possibility to consider is that
the owl was sickened by secondary poisoning from eating poisoned
rodents. The main rodenticide used by Oregon farmers, zinc phosphide, is
supposed to pose a low risk for secondary poisoning (though dangerous to
geese etc. if they consume it directly). But there are some other things
out there that could pose more of a risk:
http://npic.orst.edu/factsheets/rodenticides.html
I'll cross-post this to BOO just in case anyone wants to carry on
further with the rodenticide topic, in that forum.
--
Joel Geier
Camp Adair area north of Corvallis
i Mark
Question regarding dead barn owl
From: "Mark J. Greenfield" <markgreenfield@xxxxxxxxxxxx>
* To: OBOL <obol@xxxxxxxxxxxxx>
* Date: Sun, 20 Mar 2016 08:00:19 -0700
*
Yesterday afternoon I discovered a dead barn owl on the ground near our
barn, next to one of two very large fir trees. I did not examine it
closely, but we have experienced “owl wars” between barn owls and great
horned owls previously (the great horned owls always win, meaning for us
that we don’t see the barn owls for a while afterwards), and we know
that a great horned likes to roost in one of those fir trees. Is it
likely that a great horned killed this barn owl?
And is there anything in particular I should be looking for on the dead
owl?
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