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    Author(s): Charles M. Francis; Michael S. W. Bradstreet
    Date: 1997
    Source: In: Duncan, James R.; Johnson, David H.; Nicholls, Thomas H., eds. Biology and conservation of owls of the Northern Hemisphere: 2nd International symposium. Gen. Tech. Rep. NC-190. St. Paul, MN: U.S. Dept. of Agriculture, Forest Service, North Central Forest Experiment Station. 175-184.
    Publication Series: General Technical Report (GTR)
    Station: North Central Research Station
    PDF: View PDF  (87.44 KB)

    Description

    Long Point Bird Observatory ran pilot surveys in 1995 and 1996 to monitor boreal forest owls in Ontario using roadside surveys with tape playback of calls. A minimum of 791 owls on 84 routes in 1995, and 392 owls on 88 routes in 1996; nine different species were detected. Playback improved the response rate for Barred (Strix varia), Boreal (Aegolius funereus), Northern Saw-whet (Aegolius acadicus) and possibly Great Gray (Strix nebulosa) Owls, and reduced variance among surveys for Barred Owls. Relatively few, long stops produced the most efficient survey for Barred Owls, while more numerous, shorter stops were optimal for Boreal and Northern Saw-whet Owls. Power estimates suggest that about 50 routes per species should be adequate to detect a uniform 20 percent decline over 10 years (2.2 percent per year) for Boreal and Northern Saw-whet Owls, and a 50 percent decline for Barred and Great Gray Owls (6.7 percent per year). However, some species were detected on many fewer than 50 routes, and models of uniform population changes may not be relevant for owls. For example, 60-80 percent fewer Northern Saw-whet and Boreal Owls (P < 0.001) were detected in 1996 than 1995 on routes that were run in both years, possibly related to emigration of many of these owls out of the study areas the preceding winter.

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    Citation

    Francis, Charles M.; Bradstreet, Michael S. W. 1997. Monitoring Boreal Forest Owls in Ontario using tape playback surveys with volunteers. In: Duncan, James R.; Johnson, David H.; Nicholls, Thomas H., eds. Biology and conservation of owls of the Northern Hemisphere: 2nd International symposium. Gen. Tech. Rep. NC-190. St. Paul, MN: U.S. Dept. of Agriculture, Forest Service, North Central Forest Experiment Station. 175-184.

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