Mn Owl Invasion Update
The winter of 2004 and 2005 is still the year of the Owls in Minnesota, and now fro Wisconsin, as well. The Minnesota Ornithologists' Union (MOU) and Audubon Minnesota are working with agency and University biologists to collect data on these Owls. Records of sightings in MN should be emailed to the MOU at email@example.com.
Peder Svingen, MOU Records Committee Chair, has tallied reports thus far of 1715 Great Gray owls (GGOW's), more than 300 Northern Hawk Owls (NHOW's), and more than 400 Boreal Owls (BOOW's) in MN as of 1/17/05. This compares to last year's more typical numbers of 35 GGOW's, 6 NHOW's, and 1 BOOW's for MN and each represents the highest number ever documented in the state in a single winter season. These numbers have been adjusted to account for multiple sightings and are backed up with an Owl census coordinated by Dave Grossheusch and Jim Lind. Kim Eckert, Mike Hendrickson, and Peder Svingen also helped plan and implement this census, which will be repeated at monthly intervals through March. The first survey in early December tallied 167 Owls along randomly selected routes in northern Minnesota, plus an additional 88 owls along non-randomly selected routes.
Dave Evans and others at Hawk Ridge Nature Reserve, plus Jim Lind, Dave Grosshuesch, Frank Nicoletti, Denny Meyer and Bill Lane have banded Owls intensively this fall.. Without banding, we would certainly have missed the early Boreal Owl movements this year. 378 BOOW's have been banded this winter, 268 of these by Frank Nicoletti alone.
The MN DNR processes dead owls found and reports their freezers are filling up. 171 GGOW's, 25 BOOW's, and 2 NOHW's are logged in already, with more on the way. In the past 2 weeks, BOOW's have been regularly found roosting or feeding in the open along the North Shore of Lake Superior. Normally nocturnal, any Boreal Owl seen in these circumstances is food-stressed. Snow depth and conditions are now affecting prey availability. These factors combined with winds and bitter temperatures are exacerbating the Owls' slide towards starvation. Freezing rain coated northeastern Minnesota with ice just before New Year's Eve. Extreme arctic cold since 1/14/05 coincided with half the dead BOOW's picked up this year. According to Steve Wilson, MN DNR Ecologist, this follows the precedent of 1989, when a similar arctic blast killed off many BOOW's.
GGOW's are not surviving very well. Their penchant for sailing in front of passing vehicles adds to their mortality rates caused by other stresses. They are being seen near open farmed areas and in mixed deciduous and conifer forests. The habitat their target prey frequents is grassy open areas that are not too dry in summer. Roadside ditches, meadows, and forest edge habitats are prime vole habitat. Ditches are now packed with hard snow, forcing the owls in more from the roads. They are frequently being seen near farm buildings. NHOW's are still sticking to open, barren field edge environments, and are being seen close to where they were being seen a month ago. NHOW numbers may have stabilized; it will be interesting to see how far their dispersal takes them.
David Willard, of the Chicago Field Museum of Natural History, collected GGOW specimens from the invasion year in 1995-1996. Of the 43 GGOW's he studied, 30 were female and were more apt to be in good physical shape (i.e., carrying fat ) while the 13 males were emaciated. Dave and his colleagues theorize that the reason there were more females was that they had territories along roads where people driving by were likely to find them (dead) and where the birds could still find prey, while the males were away from roads with less accessible prey, and less likely to be found when they died. They do not know if this is true--just that it fit the data. Supporting the possibility of the sexes using different habitats was the fact that while both were feeding primarily on Microtus, the only Southern Bog Lemmings and Arctic Shrews were in male stomachs (despite a much smaller sample size for males). Dave is hoping to augment these samples this year and to see if there are similar patterns. Many GGOW specimens will be going his way. 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=birds.
The Minnesota Ornithologists' Union (MOU) is still looking for data on these owls. It is important that as much data is collected as is possible. A good record includes: 1. A correctly identified species 2. Date of observation 3. A specific location 4. Observers' names and contact information
These great birds have now dispersed throughout the northern half of the state of MN, common as far south as central Pine and Aitkin Counties. GGOW 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. GGOW's resident now in the far north are frequently found in poor condition, with fat reserves depleted and body weights very low.
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 Owls 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 within since 1/10/05. A GGOW strayed as far west as Grand Forks in late December, the first confirmed record for North Dakota since the 1960's. Another was found in Southern Iowa this week, only the fifth record for that state. In Minnesota, only a few GGOW's are being seen farther south than central Pine County as of 1/15, yet as many as a 100 are being seen in Wisconsin, so a general southward and eastward dispersal is continuing.
Why are they here?
Depletion of primary food supply has caused a mass southward movement; Lake Winnipeg forms a Western barrier to Owls from the north, funneling birds to the east of it. Boreal forest in Manitoba gives way to Prairie, so Owls would follow continuous forest SE to progress southward. Lake of the Woods is the next barricade to western dispersal. Owls would then move south to meet Lake Superior, turning SW towards the Superior National Forest and the North Shore of Superior, which we witnessed.
Where will they go?
We can confirm GGOW's have dispersed South in the past 2 weeks in large numbers to Pine and Aitkin Counties in MN and to the Southeast to Douglas and Burnett Counties in WI. A single GGOW is being reported in Iowa. NHOW and BOOW remain rare and hard to find south of Duluth. A continuation of dispersal trends may move birds deeper into Wisconsin and into Chisago, Anoka, Isanti, Sherburne and Washington Counties in Minnesota, continuing southward and eastward. Birds moving into Wisconsin may be following the continuation of boreal forest east to Crex Meadows and on. A reverse movement north and east along Lake Superior has been noted since 1/14/05. It is not known if this represents a return path to their breeding grounds o merely birds dispersing elsewhere after finding no prey to the south.
How many will survive?
We are not certain. Mortality rates are higher in Northern MN thus far.. The DNR has to get dead owls reported to them so they may determine cause of death. Birders need to disperse their activities now to report where the birds are and in what densities they are found, both in MN and in WI. Sadly, birders should look for dead owls to report to the DNR, look for their wingtips or tails sticking out of the snow. Every sighting and report is important now; each bird may become the one that stays to attempt breeding. It is a huge area to cover; we need everyone out looking for owls in promising habitat. Please remain vigilant and help us monitor the saga as it plays out. What can I do to help these birds?
You that have enjoyed these birds this year should consider giving of your time or money to some of the groups that are coordinating efforts to support these birds.
* The MOU is providing services documenting sightings, natural histories and behaviors of these birds. We will be publishing data, observations, and research from this irruption year. A special publication with photos, maps and all the data compiled is planned. http://www.cbs.umn.edu/~mou/
* The MN DNR uses funds from licenses and the "chickadee check-off" to support conservation programs and wildlife and forestry services that impact this area. Carroll Henderson, Head of the DNR Wildlife Division comments "The State is in the process of updating its list of threatened and endangered species, and it would be appropriate to review the status of these three owls to make sure that they are given appropriate consideration for listing. The boreal owl's status should be looked at very closely." Please donate and support them. http://www.dnr.state.mn.us/index.html
* Minnesota Audubon is working on Sax-Zim as an IBA (Important Bird Area), and will help coordinate development of habitat management and conservation practices with State and local organizations to ensure alignment and outcomes that are good for the Owls. 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 firstname.lastname@example.org://www.audubon.org/chapter/mn/mn/programs.html
* The Hawk Ridge Nature Reserve in Duluth sponsors banding and research; it was their contract bander, Frank Nicoletti, that showed us how many BOOW's were on the move in late fall 2004. http://www.hawkridge.org/
* Bill Lane is a bander and Owl researcher in Tofte, MN that specializes in Boreal Owls. You can volunteer to help him build or hang boxes or sponsor him in his efforts to locate breeding BOOW's and map their abundance. He uses no calls to attract birds; he only listens for actively singing birds. Last year, he heard only three BOOW's in an entire spring season. It is the hard way to do it, but it puts less stress on the birds. http://www.mindspring.com/~owlman/
* The Raptor Center has handled many injured Owls this season - 43 total: GGOW - 39 admitted; 14 survived; 3 released; 25 died NHOW - 2 admitted; 1 survived; 0 released; 1 died BOOW - 2 admitted; 1 survived; 0 released; 1 died These birds had all suffered collisions with cars and blunt trauma injuries with the exception of the Boreal that died, cause of death was starvation. All other Owls were deemed to be in good physical condition prior to their injuries. http://www.theraptorcentor.org
Supporting any of these groups by making a donation will ensure your money is put to good use. Joining up as a member can put your time to good use. We all share memberships, partnerships and interests. You should earmark donations for specific use towards Owl conservation and research or it may get applied to other worthy programs. 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. The outcome of this irruption year may be tough to witness and document, but we will see it through. I look forward to hearing Owls on territory in a couple of months, the booming hoots of a Great Gray or the hollow toots of the Boreal mixed in with the steady calling of Saw-Whets. Good Birding, go find some Owls for us, please.
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