[Birdtalk] BARN OWL MASSACRE IN IDAHO

Fri Jan 12 16:23:36 GMT 2007

Hello All -

Although a difficult event to observe without having feelings for the owls, the reason why large numbers of barn owls are periodically killed on busy roads is tied closely to their ecology.  Here in northern Utah and southern Idaho barn owls are inhabiting the northern extent of their range.  They are much better adapted to temperate and tropical conditions.  Here, during relatively mild winters, particularly those with low snow fall, barn owls are able to continue to find prey in their normal foraging environments (woodlands, fields, etc.).  However, when winters wax more severe (deeper or crusted snow accumulation) much of their small mammal prey switches to living primarily under the snow (subnivian).  In effect, the owls begin to find it very difficult to find food because they are not adapted to being able to detect and access their prey under the snow.  The natural tendency of the birds is to switch their foraging strategies from areas with deep snow to areas that are more open.  In many cases this  means roads and roadsides which are kept open by traffic and the plows.  Shoulders scrapped down to grass or gravel as well as the road itself offers opportunities for hungry barn owls to catch small mammals out in the open.  Of course the result is often collisions with vehicles.

A less common event occurring during a lower percentage of our more snowy winters are mass die offs not just associated with the roads but everywhere.  Two winters ago we had reports of hundreds of dead barn owls called into the Division of Wildlife in Ogden.  I examined a large percentage of the birds and they showed signs of death by starvation (prominent keel associated with degeneration of flight muscles).  So why do many hard winters produce dead owls on the roads, but only one in 8 or 10 produce dead owls everywhere?  A good guess at the answer again goes back to understanding the barn owl's ecology.  Barn owls are extremely prolific.  They breed their first year and can have one to two broods in a year.  It is not uncommon to have brood sizes of 6-8 owlets and up to 13 in favorable prey years.  As a result barn owls have the ability to quickly saturate their environment.  During the hard winters when barn owl populations are high competition for food resources is much worse, and large numbers of owls (likely the more inexperienced juveniles from the last breeding season) die throughout the countryside.  When the population is low, barn owls are able to squeak by making due on roadsides and windswept fields.  During these years the most obvious die-offs are occurring along roadsides.  Since the population was pruned by the late season snows a few winters ago, it is likely that the population hadn't yet reached saturation when we entered this winter's snowy season.

The good news is that these boom and bust cycles are relatively natural here on the northern edge of the barn owls range.  Although the vehicle collision undoubtably adds to winter mortality, the barn owl's outstanding ability to produce young will quickly push their population back to saturation for it all to start again in a few winters.

Enjoy the snow.  Enjoy the wildlife.  Be thankful that you can get to your refrigerator even when the snow is deep!
Cheers,
Adam    

Adam Kozlowski
Sensitive Species Biologist
Utah Division of Wildlife Resources, Northern Region
515 East 5300 South, Ogden UT  84405
Office:  (801) 476-2740
Cell:  (801) 510-2034
email: adamkozlowski at utah.gov

>>> "Gerber, Mark F." <Mark.Gerber at c-b.com> 1/11/2007 6:59:18 AM >>>
The thing to remember is that this isn't a new phenomenon.  In fact it's
been happening on that particular stretch of highway as well as
elsewhere in the world for many years.  I've been aware of it (as have
the Boise State folks doing the study) since the early nineties.  I
remember counting 92 dead barn owls along the stretch between Mt Home
and Jerome back in 1995. Those were just the ones I could see AND
IDENTIFY from the roadway at 70 mph.  It doesn't count the ones that
were thrown clear of the main roadway or were smashed beyond
recognition.

I now commute from Tooele to SLC every day and on any given day during
the winter I can see up to a dozen dead barn owls along I-80.  Once
you've seen it in one place it's easier to recognize elsewhere.

Mark F. Gerber

mark f. gerber  |  carter::burgess  |  155 north 400 west, suite 550,
salt lake city, ut 84103 |  p: 801-349-3252 |  f: 801.355.3990 |  m:
801.949.9693 |  mark.gerber at c-b.com <mailto:mark.gerber at c-b.com> 

"some see the glass as half empty, some see it as half full...I see a
glass that's twice as big as it needs to be"

From: birdtalk-bounces at utahbirds.org 
[mailto:birdtalk-bounces at utahbirds.org] On Behalf Of Gayla Muir
Sent: Thursday, January 11, 2007 6:06 AM
To: James D. McIntyre
Cc: BIRDTALK
Subject: Re: [Birdtalk] BARN OWL MASSACRE IN IDAHO

I am so glad you sent this information on.  Actually I noticed all the
dead birds at the side of the road when returning from Boise on January
3rd and was going to inquire as to where to report it - it was very
disturbing.  I coudn't believe how many there were, and that was only
the ones I could see while driving - I am sure there were many more past
the shoulder of the road.   The loss wasn't as great as I approached the
Ogden/Pocatello split after Burley and none after that.  Made me wonder
why. 

On 12/9/06, James D. McIntyre <james.d.mcintyre at att.net> wrote: 

Here are some links to recent articles about the thousands of Barn Owls
being killed by motor vehicles along I-84 in Idaho:

http://www.king5.com/animals/news/stories/NW_010607ANBbarnowlsSW.143241c 
0.html

http://www.findarticles.com/p/articles/mi_qn4188/is_20060725/ai_n1663799 
0

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