55
OWL MORTALITY
UTILITY
LINES
ON FENCES
AND
by
Richard
E. Fitzner
EcosystemsDepartment
Battelle
Northwest
Laboratories
Richland, Washington99352
ABSTRACT. McCarthy (WilsonBull. 85:477478) and Edeburn(WilsonBull. 85:478) discuss unusual deaths of Great Horned Owls due to collisions with barbed-wire
fences. This
report describes
the wire-caused
deathsof three Short-earedOwls (Asiofiammeus)andone
Great HornedOwl (Bubovirginianus)in southeastern
Washington
and adjacentIdaho during
the winter of 1973-74.
Observations of Owl Mortality
On 30 December1973 a Short-earedOwl was found dead,hangingby its right wing from
the top strandof a 4-barbbarbed-wirefence,3« milessouthwestof Pullman,Washington.A
wire barb had piercedthe skin and musclehalfway betweenthe endsof the radiusand ulna,
both of which were fractured.
On 10 January 1974 a dead Short-earedOwl was seenhangingby its left wing from a
powerline at the southerncity limit boundaryof Moscow,Idaho. It was approximately
twenty feet above the ground, making difficult the determination of the exact meansof
entanglement.
On 1 February 1974 three milessouthwestof Pullman,Washington,a dead Great Horned
Owl was found entangledin the top wire of a two-barbbarbed-wirefence(Fig. 1). The bird
was carefully untangledto obtain someclue as to how the accidentoccurred.A singlebarb
had piercedthe skin and musclewithin one inch of the distalend of the radiusand ulna. The
momentumof flying apparentlyflipped the bird over the top strand,furtherentanglingthe
wing on both barbs.No boneswere broken.
On 2 February 1974 a dead Short-earedOwl was found hangingby its neck from a
powerline200 yardseastof the Pullmanairport(Fig. 2). The wire wasoverforty feet above
the ground.Photographs
revealedthe wire to be of a twisted multi-strandtype with no
protectiveouter coating. Its coarsetexture apparentlycaughtthe fine soft feathersof the
bird's neck. I suspectthat the bird flew into the line at a veryslowspeed;the momentumof
rapid flight would certainlyhavepulledlooseany entangledfeathers.
On 28 December 1973 a live Short-earedOwl was found entangledby its neck in a
four-foot-diameter,four-foot-highroll of two-by-four-inchwovenfencingwire. The wire and
a variety of old, rusty farm machinerywere located on the edgeof a largeplowedfield 3•
milessouthwestof Pullman.The bird apparentlyhad tried to capturea smallrodent living
within the confinesof the wire. In its pursuit,it managedto wedgeits neck between two
strandsof wire and was unableto escape.The owl was in an extreme state of exhaustionbut
recovered within 24 hours after rescue.
The discovery of three deaths and one near-death of Short-earedOwls reflects their
abundanceduringthe winter of 1973-74 in the farmlandsabout Pullman,Washington,and
Moscow, Idaho.
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RAPTOR RESEARCH
Vol. 9, No. 3/4
Discussion
The Great HornedandShort-earedOwlsfound impaledon barbedwire fencesare interest-
ing cases.Thesebirdswerehuntingin bareplowedfields.The onlyhabitatavailableto their
prey (smallrodents)wasnarrowweedycorridorsalongfencerowsor areastoo steepor too
rocky for cultivation.In suchsituationsthe owlswere constantlyconfrontedwith barbedwire fences.If they had no priorexperience
with suchfences(i.e.,birdsof the yearor ones
raised in areaslacking fences),they might simply have perceivedthe fencesas movable
vegetationwhichwouldhavecausedinsignificantdisruptionto their flight.
The owls that collidedwith powerlinesmust havedone so under different circumstances.
The powerlines
werehigherin the air, and a huntingowl wouldprobablyhavebeenflying
closerto the ground,thusavoidingthem. The owlsmay havebeenflyingto a huntingpost,
possiblythe powefiine itself or its supportingpole, and somehowcollided with the line.
They possiblywere forcedinto the line by a gustof wind. I haveviewedseveralShort-eared
Owlsbeingblown off courseby the stronggustsof wind characteristic
of winter weatherin
the study area.
Collisionslike thesewill probably continue to occur in the farmlandsnear Pullmanand in
other areasof the countrywherefencestraversethe huntinghabitatsof owls.The problem
may be compoundedwhere owls are particularly abundant. Owls with nomadictendencies,
like the Short-earedOwl, probablysufferthe greatestlossesfrom collisions,
sincethey lack
familiarity with their surroundings.
Age may also be a factor in that youngbirdswith
relativelylittle huntingexperience
may be moresubjectto suchcollisions.
Agewasimpossibleto determinein any of the birdsreportedin this study.
The frequencyof wire-collisions
by owlsremainsan openquestion.However,it maybe
worthwhileto identify trouble spotswhereone or moremishapshaveoccurredand to work
out someplanto reduceor eliminatefuture accidents.For example,old, unusedbarbed-wire
fencescould be removed.Fencesin use could be markedwith stripsof ribbon or foil to
increasetheir visibility.
Fall-Winter1975
Fitzner - Owl Mortality
Fig. 1. GreatHornedOwl impaledon a two-barbbarbed-wirefence
Fig. 2. Short-eared
Owl hangingfrom a powerline
57