BOREAL OWL HABITAT QUESTIONS
steppie at nwinfo.net
Fri Oct 13 05:26:21 PDT 2000
Barry Levine sent a query to me regarding our (Ellen, Denny Granstrand, and
memorable encounter with Boreal Owls in the upper reaches of the Middle Fork
of the Ahtanum drainage west of Yakima 11 October:
Sounds like you guys had great luck!
Last Sat. night on Mt. Rainier, Rick Romea, Jack Stephens and myself had a
similar experience at the top parking lot at Sunrise. We first heard a skiew
call and then the mournful two syllable cry that you alluded to. We
eventually got a good look (albeit short) at it perched in a tree. Kevin
Aenerude and a friend were also successful at that location, as well as
Patrick and Ruth Sullivan, who were searching out of the lower parking lot.
A question for you in that Patrick and Ruth talked about seeing juveniles in
a previous post. My recollection is that there are no records of breeding
Boreal Owl's on Rainier. Is that correct? Also will these birds likely
migrate out of the area? I know that during the winter it would be hard to
track them, but has any work been done in this arena in the past? I figured
I'd run these questions by you since you seem to be the person most up on
owls around here. Thanks for any help. Hope you're doing well.
There is but one proven record of breeding of Boreal Owls in Washington -
that of a pair fledging 5 young from a box at Thirtymile Meadows in the
Okanogan Highlands in June 1992 ( a project I initiated with the Okanogan
National Forest specifically to prove breeding in the state, my aim being
recognizing Subalpine Zone forests of that area as worthy of preservation
not only for Boreal Owls, but also Lynx, Northern Bog Lemmings, and even a
number of rare plant communities). See: Stepniewski, A. 1992. Boreal Owls
found nesting in Washington in 1992. Washington Birds 5: 55-60.
I suspect this species breeds in Subalpine Fir dominated forests on the
relatively dry northeast side of Mt. Rainier (where snow fall and duration
of snowlie is significantly less than on the windward slopes as at Paradise
only a short distance away. At Paradise, the forests are dominated by
Hemlock, the dominant tree species of the "Snow Zone," where winter
snowdepth is great and duration of snowlie prolonged, typically eight months
Proving breeding of this elusive owl is easiest with a systematic
nest box program.We (the U.S. Forest Service and myself) had 110 boxes in
the Okanogan Highlands, with occupancy proven only once in 1991, and once
again in 1992. Thus, dogged determination is required; go try and
build, erect, and monitor 110 boxes!
Good information on the post-breeding movements and whereabouts of this
species in the mountains of western North America is known from data
collected in the Frank Church Wilderness in north-central Idaho. There, Pat
and Greg Hayward determined Boreal Owls performed impressive diurnal
altitudanal movements, encompassing a tremendous areal extent (even putting
Spotted Owls, well-know for their huge home ranges, to shame).
A March record of a Boreal Owl caught in a mist net in the Okanagan Valley
of southern British Columbia is further evidence Boreal Owls perform
altitudinal movements (Cannings Birds of the Okanagan Valley, BC.)
I would suspect Boreal Owls in Washington undertake similar daily and
movements, particularly to zones below the belts of heaviest snowlie.
Indeed, depth and duration of snowlie may well be the major factor limiting
Boreal Owls from successfully colonizing maritime portions of the Subalpine
Zone (somebody needs to test this hypothesis).
Last night I chose to stop at and near Clover Flats Campground because I
judge the meadow and forest edge near the campground attractive habitat for
breeding Boreal Owls, based on the Thirtymile Meadows pair in 1992 and my
experience in the Horseshoe Basin area of the Paysayten Wilderness, where
Bob Boekelheide, Ike Eisenhart, and myself heard (primary call) Boreal Owls
very briefly each evening in July on a 4-day trip there. I suspect juvenile
Boreal Owls and their parents might, for the most part, reside in their
natal territories until winter comes, when prey availability is surely
reduced, thus forcing
the birds to disperse. Radio-tracking, however, reveals some dispersal
immediately after fledging, but it stands to reason juveniles in particular,
will hang around their nest territory until forced to move.
steppie at nwinfo.net
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