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Explains bird choice for a project in which matched filters and spectrographic analysis were used to identify birdcalls.

Bird choice

We elected to use six different birdcalls in our project: the common loon wail; the common loon tremolo; the red-tailed hawk cry;the red-tailed hawk shriek; the bobwhite quail mating-call; and the ferruginous pygmy-owl hoot. The group selected these calls based upon two major criteria.Each call needed to be available from multiple sources, and each call had to be audibly different from the other calls selected.

The project group contains no bird experts, so we used only prerecorded birdcall clips as samples. Such audio clips saved us thenecessity of making field recordings. Also, the clips’ creators, who presumably possess more ornithological expertise than we, had already identified the birdspresent in each recording. For formatting reasons, we chose only audio clips saved as wav files. However, with this constraint, relatively few bird typessuited our needs. Adults of each bird species have up to fourteen or fifteen call types. Of these types, frequently only one or two are available asrecordings, and of recorded types, almost none exist in multiple, wav-file examples on the internet, or in libraries. This significantly reduced our poolof candidate birds.

Our second major criterion was that the chosen birdcalls be audibly and spectrographically distinctive. Although spectrographicanalysis can easily reveal differences between signals in the frequency domain, human error is less likely when group members can tell the difference betweentime-domain calls by ear. Having a variety of birdcalls, some similar, some radically different, also produces a more interesting analysis than the use ofentirely alike, or entirely dislike calls.

The application of both criteria resulted in the final selection of birds.

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Source:  OpenStax, Birdcall identification project. OpenStax CNX. Dec 17, 2008 Download for free at http://cnx.org/content/col10616/1.2
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