Statistical Analysis of the Feeding Call of Nestling/Fledgling Barred Owls (Strix Varia) in West-Central Illinois

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Woodyatt, Keston Roy
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Western Illinois University
Feeding calls of 12 barred owl (Strix varia) nestlings/fledglings from 5 nests, at 3 locations, in Macomb, McDonough County, Illinois, were studied during the spring and early summer from 1991 to 1993 in the laboratory and natural settings. A total of 246 nestling/fledgling feeding calls were recorded and analyzed. The duration and frequency were analyzed for each call using Canary software for the Macintosh computer. The feeding calls recorded in the laboratory were no different than those recorded in natural settings. Principal Component and Discriminant Function analyses of the feeding calls of 12 barred owls were conducted on 4 study groups for determination of any differences. Three study groups were named based on their locations in Macomb, Illinois: Chase Street, Lafayette Street, and Spring Lake. These study groups consisted of adult barred owls and nestling/fledglings recorded at nest sites. A fourth group, the laboratory group, was comprised of 4 nestlings (2 from each nest) from 2 separate family groups recorded in a laboratory setting. The feeding calls of the 4 study groups were statistically different. The structure of the feeding call of nestling/fledgling barred owls was simple compared to the feeding calls of other young altricial birds. The barred owl nestling/fledgling feeding call usually began between 6.5 and 7.0 kHz and maintained this frequency until the end of the call where it sharply dropped to around 4 kHz. The call was approximately one second in duration. The feeding call of barred owl nestlings/fledglings was found not to be age-dependent. The feeding call of a nestling barred owl was the same as the feeding call of the fledgling barred owl. Discriminant Function Analysis classified the 246 nestling/fledgling feeding calls into one of the 4 study groups. On average, 84.0% of the calls were matched with the correct study group.