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This page is meant to serve as a resource for all those
working on Short-eared Owl research and conservation. The
Short-eared Owl can be a difficult species to study, and while
techniques that are successful in one part of its range may not
necessarily be as effective elsewhere, sharing tips should nonetheless
reduce the learning curve for those with less experience, and may help
in developing standardized approaches to habitat and population surveys.
We welcome all
contributions, either as files (images, videos, text) to be posted
on this page, or as links to other existing sites.
Historical data:
MRF has requested and received from the Bird Banding Office a copy
of the list of all Short-eared Owl banding recoveries in North
America as of November 2006. We are grateful to the many banders who contributed to
this data set over the past century.
We will prepare a more detailed summary of the
file, but can provide here a few simple statistics from our preliminary
analysis. A total of only 50 recoveries have been reported,
ranging in date from 1923 to 1997. Of these, 29 were banded in
Canada (17 British Columbia, 4 Alberta, 1 Saskatchewan, 1 Manitoba, 2
Ontario, 2 Nova Scotia, 2 Newfoundland and Labrador), and 21 in the
United States (1 Hawaii, 2 Washington, 1 Oregon, 1 Utah, 1 Idaho, 1
North Dakota, 2 Wisconsin, 1 Kansas, 1 Oklahoma, 3 New York, 1 New
Jersey, 3 Delaware, 3 Massachusetts). Nearly two-thirds (66%) of
individuals were recovered in the same state/province as banded, and 30%
were in fact banded and recovered within the same 10-minute block.
Some individuals, however, did cover substantial distances, with 8
individuals recovered more than 1000 km from where they were banded (see
map below).
The longest span between banding and recovery was 4 years, 2 months.
The vast majority (84%) of recoveries were of
dead birds. Of the 18 mortalities for which a cause of death was
known or presumed, the most common were aircraft collisions (3), highway
deaths (6), and shooting (7). Eleven of the birds were banded as
nestlings or recently fledged juveniles, 8 others as hatch-year birds,
and 24 as after-hatch-year birds, with the age of the remainder unknown.
Sex was reported as unknown for all but one male and one female,
suggesting that future banders should make it a priority to attempt to
determine sex if at all possible, either through a combination of
measurements and plumage characteristics, or by collecting a feather
sample for testing (only if in possession of a valid permit for that
purpose). Photographing any birds banded to develop a visual
reference library of known age/sex Short-eared Owls would also be
valuable.
Map of all known
long-distance (>50 km) banding recoveries, showing original (black) and
recovery
(red) coordinates. (Map provided by Geoff Holroyd, Canadian Wildlife
Service)
Telemetry data:
MRF is currently tracking a female Short-eared Owl from Saskatchewan
using satellite telemetry - click here for
the latest updates. Only a few other individuals have been studied
in this manner previously - two from Alberta, and two from New York.
Pete Nye of the New York State Department of Environmental
Conservation's Endangered Species Unit has kindly shared with us the
results of his studies (see maps below). Interestingly both
individuals were trapped in eastern New York in late winter and tracked
to Labrador in spring/summer.
Map showing all known
locations of the Short-eared Owl tracked in spring 2006; note that very
few data points
were received from the transmitter over a period of several months (map
provided by Pete Nye).
Map showing the movements of
a Short-eared Owl banded and fitted with a transmitter in eastern New
York
in March 2007, and tracked for two months to western Labrador (map
provided by Pete Nye)
Survey protocols:
A few provinces and other agencies have developed standardized
protocols for Short-eared Owl surveys, and there is a general sense that
it would be desirable to develop a common approach that could be used
across Canada (and beyond) in an effort to standardize results and
enable comparison among regions. We hope to obtain permission to
post or link to some of these protocols here. The Newfoundland and
Labrador
Management Plan includes a survey protocol tested in that province. A recent British Trust of Ornithology Research Report (Calladine et al. 2008) provides a detailed assessment of field monitoring efforts of breeding Short-eared Owls in Scotland, which may be largely applicable to other areas as well, as does a previous report by Calladine et al. (2005) providing background information on the development of survey techniques.
Habitat classification:
Accurately describing the critical habitat of Short-eared Owls is
one of the key challenges facing researchers. Vegetation
inventories, photo documentation, and interpretation of topographic maps
have all been used in different areas, with varying levels of success.
As with population surveys, it would be advantageous to develop a
technique that could be applied throughout the species' range.
Capture and banding techniques:
Note: the following techniques are to be
used only by those in possession of a valid banding permit with
authorization for Short-eared Owls.
Researchers have reported success (and failure) with a
variety of capture techniques. We present here a brief summary of
comments we have received, and welcome any further
commentary or suggestions from those who have experience with this
species.
Bownets, especially those with an automated
release trigger, have proven to be quite effective at capturing
Short-eared Owls.
Bal-chatri traps, though useful for many
raptors, seem to rarely be successful with Short-eared Owls.
Experience suggests that while the owls are attracted to the traps, they
tend to be too wary to actually land on them.
Mist nets may be effective in some
circumstances, most notably during the nesting season when adults are
likely to be aggressively defensive. The nets are most likely to
be successful if an audiolure is used, and/or a predator decoy is placed
conspicuously beside the net. Some have also found nets to work in
the absence of such lures, if the net is placed in tall grasses, and a
narrow lane is mowed on either side of it; the opening provides easier
access for the owls to their prey, and they may hit the net in the
course of hunting.
Leasure and Holt (1991) report on the successful use of a
horizontally held mist net, that can be lowered over nests to catch
the female and/or young.
Verbail traps are difficult to find, and can
be tricky to learn to use, but are among the best tools for catching
Short-eared Owls, especially in areas where natural perches are scarce.
Click here for a few photos of a verbail trap, and a brief poor-quality
video that gives some sense of how the trap is triggered.
Links:
Birds of North America Online (subscription required)
Includes the full Short-eared Owl species account, updated in 2006 by
Wiggins et al., which provides a comprehensive overview of the
species.
Environment Canada Species at Risk - Short-eared Owl
A fairly detailed page including notes on distribution and research
and recovery efforts.
Northern Prairie Wildlife Research Center: Effects of Management
Practices on Grassland Birds - Short-eared Owl
A thorough review from 2003, particularly useful for habitat
descriptions and management recommendations.
Bird Studies
Canada - Short-eared Owl research
A summary of conservation concerns and population surveys in Ontario.
Status of the Short-eared Owl in Alberta
A thorough review of the provincial status as of 2000, with much
information also applicable to other parts of its range.
A Management Plan for the Short-eared Owl in Newfoundland and Labrador
A detailed summary of Short-eared Owl status and research/management
potential, also potentially widely applicable.
British Columbia Ecosystem Explorer - Short-eared Owl
Enter "Short-eared Owl" in the search box to access a variety of
references on the status and study of the species in British Columbia.
New York State Department of Environmental Conservation - Short-eared
Owl fact sheet
An overview of the biology and status of Short-eared Owls in New
York, including maps.
The Owl Pages - Short-eared Owl page
A good brief summary of the Short-eared Owl, including photos and
sound files.
Owling.com - Short-eared
Owl page
Another site with a good overview accompanied by photos and sound
files.
Owl Research Institute
A site that includes a brief outline of research conducted on
Short-eared Owls and several other species.
Do you manage or know of
a Short-eared Owl website that should be listed here?
E-mail
us the link.
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