Subject: [Tweeters] Fwd: Part two of two--Some observations and speculation
Date: Mar 20 14:15:41 2010
From: notcalm at comcast.net - notcalm at comcast.net











Hello Tweeters Community members. This is Part two of a two part e-mail, split because of size limitations of this list serve.

All of the below material was extracted and quoted from the Cornell Ornithology Website, Birds Anline . I would highly recommend this site for researched based information, especially when unusual situations like the present one occur. I have highlighted ( BOLD type ) some key points:

Continued from part one e-mail.----------------------------------------------------------------------------------------------------------------------------------------------------------------------

?Burrowing Owls found as prey remains in Swainson?s Hawk ( Buteo swainsoni ) and Ferruginous Hawk ( B. regalis ) nests. Merlins ( Falco columbarius ), Prairie Falcons ( F. mexicanus ), Peregrine Falcons ( F. peregrinus ), Great Horned Owls ( Bubo virginianus ), Red-tailed Hawks ( B. jamaicensis ), Cooper?s Hawks ( Accipiter cooperii ), and American Crows ( Corvus brachrhynchos ) have all been seen or suspected as predators of adult and young Burrowing Owls (BAM, Wedgwood 1978 , Konrad and Gilmer 1984 , Millsap and Bear 1988 , Martell 1990 ).

?Nutrition And Energetics

Energy expenditure calculated as 15.5 ? 1.86 kcal/d ( Coulombe 1970 ). Based on finding owls in burrows after many days of inclement weather, it has been suggested that Burrowing Owls may be capable of fasting for several days ( Aggersborg 1885 , Butts 1976 ). The owls appear to be generalists when preying upon insects ( Plumpton 1992 ).

?Historical Changes In Distribution

Extirpated from British Columbia in recent years; last confirmed sighting in 1979. Since 1983, > 400 released in that province, 13 returned in 1992 ( Haug et al. in press ). Elsewhere in Canada and the n.-central U.S., range has contracted slightly southward, westward, and eastward ( Haug et al. in press , Martell 1991 ).

?Nature Of Migration In The Species

Most of the North American population is migratory or disperses widely to some extent.

?Timing And Routes Of Migration

Little information on migration routes, times and wintering areas. The majority of owls that breed in Canada and the n. United States are believed to migrate south during Sep and Oct, north during Mar and Ap r , and to the first week of May in Saskatchewan (see Fig. 3 ). Owls are predominately nonmigratory in Florida ( Millsap in press ) and s. California ( Thomsen 1971 ), although owls in n. California are believed to migrate ( Coulombe 1971 ).



?The small number of banding recoveries (27 between 1 Nov and 28 Feb, 1927 to 1990 inclusive) provides little information regarding wintering areas. Owls banded in the west (British Columbia, Washington, Oregon, California) show a southern migration along the coast and , in one case, into Mexico.. Banding recoveries suggest that Canadian owls migrate further south than those banded in the United States, suggesting a ?leap-frog? migration ( James 1992 ).

?Hunt by walking, hopping, or running along the ground; flying from a perch ; hovering, particularly over tall vegetation; and fly-catching in the air ( Grant 1965 , Thomsen 1971 , Marti 1974 ). Hunting style varies with type and activity of prey pursued, time of day, and vegetative substrate ( Thompson and Anderson 1988 ). Prey caught with the feet, but may be transferred to the beak for carrying or presentation to young.?



Recommended Citation

Haug, E. A., B. A. Millsap and M. S. Martell. 1993. Burrowing Owl ( Athene cunicularia ), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu/bna/species/061

doi:10.2173/bna.61













Best regards,




Dan Reiff

MercerIsland

"Dan Reiff, PhD" <notcalm at comcast.net>;