We might at this point be suffering from owl-information overload. Risking that, however, I offer the following comments from Dr. James Duncan, owl expert from Winnipeg. Several days ago, I asked him some questions about Great Gray Owls, which he kindly answered. Jim Williams Wayzata, Minnesota
Begin forwarded message: From: "Duncan, James (CON)" <[email protected]> Date: January 12, 2005 4:05:11 PM CST To: "'Jim Williams'" <[email protected]> Cc: "Duncan, James (CON)" <[email protected]> Subject: RE: questions on Great Gray Owls Hi Jim, Thanks for the opportunity to help. I will do my best to answer your questions below. I will use CAPS TO ANSWER, which I hope are not too annoying, but will serve to help id my responses. Cheers, Jim _________________________________________ Dr. James R. Duncan, Manager Biodiversity Conservation Section Wildlife and Ecosystem Protection Branch Manitoba Conservation Box 24, 200 Saulteaux Crescent Winnipeg, MB R3J 3W3 204-945-7465 work 204-945-3077 fax [email protected] Subject: questions on Great Gray Owls 1. Is it reasonable to believe that the Great Gray Owls we are seeing here right now are stressed to any degree simply by their displacement? MIGRATION IS A DANGEROUS TIME FOR ANY ORGANISM, INCLUDING HUMANS. Is the need to find food, which has brought them here, by itself at this point stressful? YES, BUT ONE AUTHOR OF ANIMAL BEHAVIOUR NOTED BEAUTIFULLY ... STRESS AND EMOTION ACT AS POWER UNITS, PUSHING AN ORGANISM FROM FROM ONE SITUATION TO ANOTHER. THE POINT IS THAT SOME STRESS IS BENEFITIAL (ENABLING SURVIVAL), TOO MUCH IS HARMFUL. 2. Is there reason to believe that owls encountering objects with which they are not familiar or might not be familiar (vehicles, trains, power lines, multiple and frequent observers) are stressed by those experiences? WISONSIN BIOLOGIST DON FOLLEN WROTE AN ARTICLE IN PASSENGER PIGEON DESCRIBING THE PHENOMENON OF FOCAL CONCENTRATION IN OWLS. WHEN AN OWL IS CONCENTRATING ON A VOLE IT MAY FLY INTO THE PATH OF AN ONCOMING CAR SEEMINGLY UNAWARE THAT THE CAR IS THERE. IT SEEMS THAT MANY OWLS, AND MANY OTHER FORMS OF WILDLIFE, ARE SIMPLY NOT ADAPTED TO AVOID FAST MOVING VEHICLES, A RELATIVELY RECENT PHENOMENON FROM AN EVOLUTIONARY PERSPECTIVE. IN MY OPINION, MANY OBSERVERS AT A RESPECTFUL DISTANCE, WOULD NOT STRESS A FREE-LIVING HUNTING BIRD. REPEATEDLY APPROACHING A BIRD TOO CLOSE CAUSING IT TO CHANGE PERCHES FREQUENTLY IS NOT APPROPRIATE BEHAVIOUR AND LIKELY STRESSFUL TO THE ANIMAL. FOLLOWING RADIO-MARKED GREAT GRAY OWLS FOR MANY YEARS TAUGHT ME HOW CLOSE I COULD APPROACH - IT VARIES BETWEEN BIRDS, AND YOU HAVE TO TAKE THE CUES FROM THE OWL. I ALSO LEARNED THAT IN THE WILD GREAT GRAY OWLS HAVE ACCIDENTS, DAMAGING THEMSELVES ON SHRUBS AND WILLOWS. YES, SOME COLLIDE WITH WIRES, FENCES, ETC. BUT MOST SEEM ADEPT AT AVOIDING THEM. I THINK THEY BENEFIT FROM POLES USED FOR HUNTING PERCHES. RELATIVELY FEW GET ELECTROCUTED BY POWER LINES. 3. Can this stress, if it exists, be a factor in the birds' ability to successfully hunt? LIKE PEOPLE, A STARVING OR TIRED BIRD IS MORE ACCIDENT PRONE AND MORE VULNERABLE (LESS WARY) TO PREDATORS SUCH AS GOSHAWKS, GREAT HORNED OWLS, LYNX, MARTEN, ETC. 4. What is the usual success ratio for a hunting owl? How many strikes might it make before successfully capturing prey? ADULT BIRDS ARE MORE EFFICIENT HUNTERS THAN LESS EXPERIENCED BIRDS. IN 1992 I ESTIMATED SUCCESS RATES FOR WINTER HUNTING GREAT GRAYS, BUT THIS WAS BASED ON A RELATIVELY SMALL SAMPLE -- 30 TO 50 % OF SNOW PLUNGES WERE SUCCESSFUL. I WOULD CAUTION AGAINST USING THIS ESTIMATE TO JUDGE IF A HUMAN ACTIVITY IS IMPACTING OR STRESSING GREAT GRAY OWLS. MORE RESEARCH IS NEEDED ON HUNTING SUCCESS RATES. 5. How many voles must an adult Great Gray Owl eat during an average winter day to survive? 4-6, DEPENDING ON HOW BIG THE VOLES ARE. 6. How long can a Great Gray Owl go without food before it becomes to weak to hunt? I DON'T KNOW, BUT I WOULD GUESS ABOUT A WEEK IN WINTER. THE PROBLEM IS THAT AS A BIRD GETS HUNGRY, IT GETS ACCIDENT PRONE AND MORE VULNERABLE TO PREDATION. 7. We are approaching a period of several days of predicted below-zero (F) temperatures. What impact will this colder weather have on the birds' need for nourishment? CLEARLY COLD WEATHER INCREASED THEIR NEED FOR FOOD, BUT THE PLUMAGE OF A GREAT GRAY KEEPS IT QUITE WARM IF IT IS SHELTERED FROM THE WIND. IF THEY ARE EATING WELL THEY CAN SURVIVE EXTREMELY COLD WEATHER. 8. How best can observers meet the needs of the birds during periods of observation? Should observation be limited overall? Should there be limits to approach? Should there be limits to duration of observation? Are there clues an observer can use to determine if the owl is becoming stressed or agitated, to determine that an observation should be terminated? PEOPLE SHOULD USE COMMON SENSE - SEE MY EARLIER COMMENTS. WATCHING THEM FROM A CAR OR THE ROAD WITH BINOCULARS AND SCOPES SHOULD NOT STRESS THE BIRDS. WALKING OUT ACROSS A FIELD RIGHT UP TO THE TREE IT IS PERCHED IN TO SEE IT CLOSER IS NOT SOMETHING I WOULD DO. ALONG ROADS, I TYPICALLY KEEP AT LEAST ONE TELEPHONE POLE AWAY FROM A BIRD ON A HYDRO POLE. 9. What advice might you offer birders as they seek to balance their continuing desire (repeated trips by some individuals) to see as many of the birds are possible with their desire to do no harm to these creatures that, to some degree, have placed themselves in our care? I THINK MY COMMENTS ABOVE ADDRESS THIS. HERE IS ANOTHER POINT I'D LIKE TO MAKE. I USE AN ARTIFICIAL MOUSE OR VOLE-LIKE LURE TECHNIQUE TO CATCH AND BAND GREAT GRAY AND NORTHERN HAWK OWLS. I PERSONALLY THINK FOR THIS PURPOSE IT IS AN ACCEPTIBLE TECHNIQUE -- IT IS USED ONCE, AND THE BIRD IS RELEASED WITHIN MINUTES OF CAPTURE. I KNOW SOME PEOPLE IN MANITOBA WHO HAVE USED ARTIFICIAL LURES TO BRING OWLS CLOSER TO PHOTOGRAPH THEM, AND SOME DID SO REPEATEDLY. I AM OPPOSED TO THIS PRACTISE SINCE IT CAUSES THE BIRDS TO EXPEND ENERGY REPEATEDLY. I SOMETIMES GET ASKED IF FEEDING OWLS LIVE OR FROZEN-THAWED LAB MICE IS OK, FOR PHOTOGRAPHY OR SIMPLY BECAUSE WELL-INTENTIONED PEOPLE WANT TO HELP HUNGRY OWLS. I THINK THIS PRACTISE HAS PROS AND CONS. PROS - THE OWLS GET SOME FOOD ENERGY FOR THEIR EFFORT, AND THIS WOULD COMPENSATE THE OWLS FOR THE ENERGY THEY EXPEND (RE PHOTOGRAPHERS). CONS - THIS PRACTISE HAS BEEN SHOWN TO CONDITION SOME OWLS TO APPROACH PEOPLE AND CARS IN ANTICIPATION OF BEING FED. ONE OWL NEAR WINNIPEG WAS NICKNAMED "LUNCHBOX" BY THOSE FEEDING IT. SUCH CONDITIONED BEHAVIOUR MAY LURE SOME OWLS TO THEIR DEATH IF THEY APPRAOCH HIGH TRAFFIC AREAS, OR PEOPLE NOT FAMILIAR WITH THE CONTEXT (THEY ASSUME THE OWL IS ATTACKING THEM AND MAY HARM THE OWL IN SELF DEFENSE. AS A GENERAL POLICY, IT IS ILLEGAL TO FEED WILD ANIMALS IN MANITOBA UNLESS IT IS FOR DEPARTMENT APPROVED CONSERVATION PURPOSES OR PERMITTED RESEARCH. MN MAY HAVE ITS OWN POLICY ON THESE MATTERS. HOPE THIS HELPS!
