RESEARCH

SHORT-EARED OWL

RESULTS

Skor - rehabilitated at the Owl Foundation in Ontario; released in Saskatchewan October 2007

 
 

 

Scroll down or click here to access the latest reports on Skor's movements

Background:
The Short-eared Owl has been experiencing a severe population decline over much of North America.  One of the key challenges faced by conservation efforts is that it is a highly nomadic species and few details are known about its movements; this also makes it difficult to accurately assess the population at any given time.  Recent advances in satellite telemetry have resulted in transmitters finally being small enough to be worn by Short-eared Owls.  This technology now provides a unique opportunity to investigate this critical issue.

To our knowledge, the first satellite transmitter was deployed on a Short-eared Owl in New York in 2006, and only two other individuals have been tracked since.  Results in all cases have been limited; the reason for this is unknown, but one possibility is that the back feathers are covering the solar panels on the transmitters, limiting their ability to gather enough power to send a signal to the satellites orbiting Earth. 

To better understand what is happening and improve our chances of a successful tracking effort, we chose to deploy our first satellite transmitter on an owl in captivity.  This provided an opportunity to monitor the reliability of the transmitter and make adjustments prior to release.  Also, while previous studies on a variety of other raptor species have suggested that wearing a satellite transmitter does not influence behaviour, this also gave us a period of observation to verify that neither it nor the harness were inhibiting the bird in any way.  An added benefit of this approach is that relatively little is known about the movements and survival of birds following rehabilitation, and this research will begin to provide some insights into this.

The bird selected for our study is a third-year female named "Skor", originally rescued by the Saskatoon Veterinary College in Saskatchewan.  In January 2006, she was transferred to the Owl Foundation in Vineland, Ontario for rehabilitation.  Once she had replaced enough of her damaged feathers to fly effectively, she was placed in a 75 m long flight cage to strengthen her flight muscles and resume catching prey.  As her moult was not completed until late in the year, she was held over winter again, and received extensive flight and hunting training prior to her release back to Saskatchewan in October 2007.

The 12-gram transmitter worn by Skor is powered by solar energy, and should continue broadcasting for at least two to three years.  Although the longevity of Short-eared Owls has not been well studied, it is generally believed that they are a very short-lived species, so there is a good chance that the transmitter may in fact have the longer lifespan.  If that should be the case, we hope to be able to use the opportunity to learn more about the causes of mortality that threaten this species.

The raw satellite telemetry data will come to MRF by e-mail, and we will provide regular summary updates below, in reverse chronological order.  We will aim to provide updates on roughly a weekly basis, but may post news sooner if there is a lot of movement, or somewhat less frequently if the bird remains stationary for extended periods.  Maps will also be updated periodically to provide a visual overview of Skor's movements.

Quick links:


Short-eared
Owl profile

Project outline

Satellite telemetry
information

The Owl Foundation


All photos by Kara Kristjanson unless otherwise credited

 

Questions or comments?  Please e-mail MRF Research Director Marcel Gahbauer.
Tax-deductible donations to help us continue and expand this research program
are greatly appreciated - click here for more information



Map last updated 15 November 2007


Reports:

27 January 2008:  
Fremont, IA
Two months have passed since the last data transmission from Skor.  We kept putting off this update, hoping that data would suddenly come in, as happened following the original period of suspense in October - but that was only two weeks.  Certainly a silence this long is not encouraging.  However, there is also no evidence to suggest that Skor has perished - from past experience with satellite telemetry studies of other species, we know that mortalities are often recorded as a lack of movement by the transmitter; receiving no data at all leaves the situation less clear.  Only a few Short-eared Owls have previously been studied using satellite telemetry, and in at least two cases there were long periods of a month of more during which the transmitter was silent, only to become active again.  Considering that it is powered by solar energy, winter days are shorter, and Skor is probably spending much of the day seeking shelter, it could well be that the transmitter simply has not been able to collect enough of a charge to function.  If this is the case, then as days get longer again and Skor becomes more active heading into migration and then the breeding season, it could well start broadcasting again.  In the meantime, all we can do is wait and hope.  We will post an update as soon as any data are received.

24 November 2007:  
Fremont, IA
Little has changed, with new reports on November 20 and today showing that Skor has remained in the same area of southeast Iowa.  All signals have come from within a few kilometres of each other.  Perhaps she has settled into a winter home this time.

15 November 2007:  
Fremont, IA
Skor seems to travel when we're not 'watching'!  When we got data two days in a row, she barely moved; now that there has been a four day gap between reports, we find that she has made a major shift to the southeast of over 460 km.  Her present position is roughly midway along and 50 km south of the line connecting Des Moines and Iowa City, in southeastern Iowa.  Although the transmitter has the potential to provide us with data daily, it only emits a signal when the solar panels have received a sufficient charge - and that of course can be influenced by weather, day length (it's a good thing she's heading south!), and most importantly, Skor's behaviour.  Seeking shelter in concealed places is good for avoiding predators, but tends to limit the exposure of the transmitter to direct sunlight.  While it's frustrating to be missing out on some of the details of her movements, the quality of data should remain consistent over a much longer period than for a battery-powered transmitter - and in any case, the solar-powered units are the only ones light enough for a Short-eared Owl to carry.  Despite being left to guess at what happened during the gaps, we have already learned a surprising amount over the first month of Skor's movements.

11 November 2007:  
Marshall
, MN.  Little change in position today, although the latest data show that Skor is now right along the Redwood River, northeast of Marshall.  While most of the landscape is cultivated, it may be that near the river she is finding some remnants of the tallgrass prairie that historically dominated this region.

10 November 2007:  
Marshall
, MN.  Apparently South Dakota didn't meet Skor's needs, as she has returned to the area north of Marshall where she was 11 days ago.

8 November 2007:  
Toronto, SD
No, that isn't a typo!  While Skor spent time in rehab at the Owl Foundation, she was within 50 km of Toronto, Ontario; now that she is free to explore on her own, she has somehow found her way to within 10 km of the small town of Toronto, South Dakota, population 202.  She is again in an agricultural area, just west of what appears to be a badland complex, and has moved west 40 km over the past 5 days. 

3 November 2007:  
Ivanhoe
, MN.  Skor has made a more modest movement since the last update, shifting 24 km west to near Ivanhoe, Minnesota.  This is still part of the largely agricultural landscape that she was in a few days ago.

30 October 2007:  
Marshall
, MN.  Well, after keeping us in suspense for nearly two weeks, Skor has finally checked in with a new location.  It would seem that despite our best attempts to find her a new home in good habitat close to where she was originally found, she wanted nothing more to do with Saskatchewan!  Her current location is in southwestern Minnesota, a bit over 200 km west of Minneapolis.  Her immediate surroundings are agricultural fields, but there are some wetlands not too far to the east.  Skor is now 1040 km almost due southeast of her release site.  We have no way of knowing whether she has been moving steadily or not, but that works out to an average of 80 km per day.  Now of course we are all the more intrigued to see where Skor will go next; hopefully she won't keep us waiting as long this time.

17 October 2007:  
Last Mountain Lake
, SK.  Skor is flying free!  After a long period of rehabilitation and flight training, this third-year female known as Skor has become the first Short-eared Owl to be tracked by MRF using satellite telemetry.  Our heartfelt thanks to Kay McKeever, Kara Kristjanson, Annick Gionet, and Cathy Foxcroft at the Owl Foundation in Ontario, who have put great effort into Skor's rehab, as well as closely monitoring her behaviour with respect to the transmitter and harness, and arranging for her transport back to Saskatchewan.  Thanks also to
John Auchie at WestJet and Blake Henke at North Star Science and Technology for clearing Skor to be flown home to Saskatchewan wearing her transmitter.

Given the nomadic nature of Short-eared Owls and the fact that Skor had been away for well over a year, returning her to the exact location where she was picked up was not a priority.  Rather, we decided to pick a site with an abundance of suitable habitat and a known history of supporting Short-eared Owls, while also minimizing travel time from the airport.  Last Mountain Lake National Wildlife Area, southeast of Saskatoon and north of Regina, was a good fit.

The release took place late in the afternoon.  After a quick examination to ensure both owl and transmitter were in good condition, Skor was released.  Her initial flight took her only a short distance, after which she stood on the ground for a while taking in her new surroundings.  A couple of further short flights took her deeper into the grass.  About an hour after release, distance and fog conspired to block her from view.  From now on we will rely on technology to keep tabs on her location.

It was a dismally gray day in Saskatchewan, and the preceding few days in Ontario had been rather cloudy too, so the transmitter is likely low on power.  We will need to wait for a good sunny period to charge it up before we can expect to receive telemetry data from it.  Watch this page for updates.


A view of the landscape at Last Mountain Lake, Saskatchewan, where Skor was released (Photo by Marcel Gahbauer)

April 2007:  
Vineland
, ON.  The transmitter was attached on April 13, and Skor was released back into the cage where she has been rehabilitating from her injury last fall.  The photos below show the positioning of the transmitter at rest and in flight.  After two weeks of observation, there appears to be no indication that she has any discomfort with the harness, and she has been flying impressively in advance of her release.

 

 

2002- The Migration Research Foundation Inc.