[mou] State of the state of MN Owls 2-21-05

[Alt, Mark]

The Minnesota Year of the Owls continues to engage and enthrall birders
from the U.S. and overseas. Yes, as of 2/21/05, it is still the Year of
the owls in Minnesota. The Minnesota Ornithologists' Union (MOU) and
Audubon Minnesota are still working with agency and University
biologists to collect data on these owls. Records of sightings in
Minnesota should be e-mailed to the MOU at:
 mou@cbs.umn.edu
	Peder Svingen, MOU Records Committee Chair, has tallied reports
thus far approaching 2500 Great Gray Owls, more than 300 Northern Hawk
Owls and more than 400 Boreal Owls in Minnesota as of 2/21/05. This
compares to last year's more typical numbers of 35 Great Gray Owls, 6
Northern Hawk Owls, and 1 Boreal Owl for Minnesota and each represents
the highest number ever documented in the state in a single winter
season.
	Dave Grossheusch, of the University of Minnesota - Duluth's
NRRI, reports that he and others have banded over 300 Great Gray Owls
this winter, and returns from dead birds are running about 2-3%. With
the exception of road kills, the irruption strategy appears to be
working quite well for Great Gray Owls and Northern Hawk Owls, both the
Raptor Center and banders are reporting the birds they are handling have
adequate fat reserves.
	Boreal Owls are the exception, most turned in this season appear
to be victims of starvation. This is consistent with past irruptions.
Steve Wilson, DNR Ecologist, points out that an estimate for irruption
mortality rates for Boreal Owls is much more difficult because, unlike
Great Gray Owls, Boreal Owls aren't easily counted while alive, being
more nocturnal. For the first time, though, a large number (300+) of
Boreal Owls were banded as they moved into the state last fall, so we
may get our first estimate on mortality rates as winter progresses and
more owls are recovered.=20
Thanks to all who have helped with the collection and transport of these
birds. Many nature centers, schools, and universities are benefiting
from your efforts. And in the latest example of the scientific utility
of these specimens, the Smithsonian Institute, Gary Graves, is looking
at doing an isotope analysis of recovered Great Gray Owls in an attempt
to learn their geographic origins.=20
	The MN DNR processes dead owls found and reports their freezers
are filling up. More than 500 Great Gray Owls, 73 Boreal Owls, 7
Northern Hawk Owls and 10 Northern Saw-whet Owls are logged already,
with more on the way. Taxidermists, Native American Reservations, and
Animal Hospitals are turning in birds that have been found dead in their
regions. David Willard, of the Chicago Field Museum of Natural History,
is collecting Great Gray Owl specimens from the invasion year. If you
want to check out specimen information on the owls from the 1995-96
invasion you can find it at their database at:
http://fm1.fieldmuseum.org/collections/search.cgi?dest=3D3Dbirds.

The MOU and Audubon are also collecting information on birders. Birding
as an economic benefit to rural areas can best be documented by tracking
where birders are coming from and how much they are spending.  To
accomplish that we are asking our birding visitors to let us know when
they are in the state and how much they spend, and on what (motel, gas,
food, etc). Information can be sent to:
mmartell@audubon.org

These great birds have now dispersed across the northern half of
Minnesota, common as far south as southern Pine, Aitkin, and Hubbard
counties. Great Gray Owls seen in the south are in good condition,
confirmed by banders. Southernmost birds are most active at dawn and
after 3:30 PM, actively hunting from prominent perches. Dead owls should
be reported to the local DNR office. Sax-Zim and the north shore of
Superior, where large numbers of owls were first discovered, have far
fewer birds than two weeks ago. Dispersal to the west appears to be
limited, perhaps due to the more open prairie and farmlands, but there
have been sightings as far west as Kittson, Marshall, Pennington, Polk,
and Mahnomen counties. Owls are loosely dispersed beyond this range, as
far south as Iowa, and as far west as Grand Forks. As many as a 100 have
been seen in Wisconsin, most clumped in the NW sector of the state.

FAQ's:

Where will they go?
These birds are still moving southward and are now very common around
Hinckley, MN, where they were not seen until 2 weeks ago. Dr. James
Duncan, of Manitoba, compares the Great Gray Owl to African Elephants in
that the same bird that moves south into Minnesota for this irruption
may go to the Hudson Bay region next year, and then return to the area
of their birth. He has had radio marked birds travel nearly 200 miles in
3 months. A basic pattern of increased site fidelity with increased age
and reproductive success develops. In summary, these birds will go
wherever they want, driven by the conflicting urges of food versus
reproduction.

How many Great Gray Owls are there?
There are many guesses, yet the exact amount is not known. In fact, one
of the outcomes of this irruption is the data gathered indicate where
these owls are from and helps us to estimate the overall population. The
Great Gray Owl is a circumpolar bird. Though it is found in Europe and
Asia, it frequents remote regions of each and was perhaps the only bird
classified first from the New World that is also found in the Old World.
The April 2004 issue of BIRDING listed the total population at 30,000
worldwide and remarked that 83% are in the western hemisphere, which
pegs the population in North America at just under 25,000.  Dr. James
Duncan estimates this population to be from 5,000 to 25,000. He
estimates the Manitoba Population to be between 500 and 3000 birds. It
is likely that 10% of the North American population of Great Gray Owls
is in the state of Minnesota right now, and with the inherent difficulty
of censusing a migrating species en route, we have no clear idea of how
many more than 2500 Great Grays are in-state right now, but it could be
substantial. In December, volunteers were able to find over 250 owls,
which were scattered over the entire survey area.  The biggest
concentrations were found in the Sax-Zim bog area.  In January,
volunteers were able to find over 450 owls for the weekend.  The owls
were still widely scattered, with fewer found in the northeast, but of
course, the Sax-Zim area still had the highest concentration. We started
seeing more owls south of the Sax-Zim area.=20
 Dave Grossheusch is attending this fall at UMD.  His project will be
focusing on feather isotopes of Great Gray Owls from this invasion.
Dave is planning on working with Gary Graves of the Smithsonian, and
Dave Willard of the Chicago Field Museum about getting feathers, etc. to
analyze.  This work will be done to determine the origin of the Great
Gray Owls from this invasion. It is possible to determine what latitude
a bird was at when the feather was produced. Juvenile feathers should
indicate origins of the bird. Perhaps some of the interrupted molt we
are seeing will pay off in this way, showing us where the birds were
when they grew their juvenile plumage.

How many will survive?
We are not certain. The number of dead Great Gray Owls found and turned
in now represents 20% of the birds documented to be in Minnesota.  It is
vital to get dead specimens to the DNR so they can be included in the
sample group for the study of this year's irruption. This is the largest
irruption documented in recorded history, but it is proving a very
productive strategy, so it is a safe bet it is a normal part of the
natural histories of these birds. The Raptor Center has handled many
injured Owls this season:
Total of 82 owls:
GGOW - 73 admitted; 14 survived; 3 released; 25 died
NHOW - 3 admitted; 2 survived; 0 released; 1 died
BOOW - 6 admitted; 3 survived; 1 released; 2 died
http://www.theraptorcentor.org/


What can we do?
It is time to start to mark locations of calling owls. The deep 8-10
hoots of the Great Gray Owl are distinctive and easily learned, as well
as to distinguish the Boreal's tooting from the monotone call of the
Northern Saw-whet Owl. Go to Owling.com to listen to the calls. The MOU
is working to get sample calls up on a website sometime in the near
future, as well. Specific locations (GPS preferable) are needed or birds
calling. Please note the type of call heard (see below).

What behaviors might we observe?
1.	Both male and female Great Gray Owls are giving contact calls. I
discussed at length with Dr. Jim Duncan the calls I have been hearing.
The contact note is a resonant low series of 8-10 hoots, the territorial
call. I have heard this call from 5 different owls, (all along Cty Rd 4
in Aitkin County) in the past 2 weeks. There is another call, an
upwardly inflected "yip" uttered by young and females, an expression of
to express interest bird would be a female. I heard it from a bird on a
roadside pole in the Aitkin County owl field as it witnessed an owl
plunging in the field in front of it. It called 5 times; eliciting no
response from the feeding owl, then became silent. I have recorded both
calls for that field in the past 2 weeks on video. With increasing
photoperiod, owl gonads are swelling and more aggressive/courtship
displays will be noted. A male will plunge dive where there is no prey
present just to elicit a response from a potential female, and the
chasing behavior seen is probably aggressive behavior this early in the
season, but will soon be an expression of courting behavior for males to
chase females. Any specific observations of calling behavior of these
owls should be emailed to me with location, species, time, weather
conditions, and names of observers, along with specific notes of the
bird's behavior. My e-mail is markfalcon@comcast.net
2.	Owls have been observed making direct flights up to 200 yards,
then wheeling and diving for prey. Dr. Duncan feels these birds may be
reacting to visual clues at such distance, and when close enough to pick
up the audio clues it attacks. Voles dig vent holes when through thick
crust such as we have this year, preventing toxic buildup of C02 under
the crust. They are visible,1" in diameter and can be found with pellets
near the entrance. When owls see vole activity they fly to it and plunge
where they hear it scurrying, though it is now under the ice. You can
then see the owl try to dig through the ice by doing a towhee-like hop
and scratch movement. They may either be digging to the mice or killing
them under foot.
3.	Densities seem to be at their maximum for Great Gray Owls in
Aitkin County, especially in the "Owl Field. Dr. Duncan has observed 15
owls sharing a 160 acre field at once; we are seeing 25 owls in a 300
acre field. It produces a lot of interaction and is great to witness and
capture on video if you are set up for it. Please share any observations
you may see.
4.	Watch intently for other prey to be taken than voles. There are
records of many prey species being taken this year, from rabbits and
weasels to flying squirrels. The Great Gray Owl's foraging behavior
gives it advantage to any species that roost under fresh snow. Rabbits
and Common Redpolls have been observed being taken in this manner. Try
and discern what is being eaten when an owl plunges successfully.


	Supporting any of the groups involved this year by making a
donation will ensure your money is put to good use. Joining as a member
can put your time to good use. We all share memberships, partnerships
and interests.=20
http://www.cbs.umn.edu/~mou/
www.audubon.org/chapter/mn/mn/programs.html
http://www.hawkridge.org/
http://www.dnr.state.mn.us/index.html
http://www.mindspring.com/~owlman/
	You can earmark donations for specific use towards owl
conservation and research. All of our efforts are funded by donations
and memberships. Birders and residents have been remarkable stewards
this season in Minnesota, consistently favoring decisions that favor the
owls. Good birding, go find some owls and enjoy them, sharing with us
your observations of behaviors, we all have the opportunity to ad to
what we know about these remarkable birds.

This essay is the product of all listed here and many more,

Mark Alt
President, Minnesota Ornithologists' Union
markfalcon@comcast.net
(Cell) 612-803-9085
Brooklyn Center, MN=20


Mark Alt=20
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(Cell) 612-803-9085