A field evaluation of the effectiveness of distance sampling and double independent observers to estimate detection probability in aural avian point counts
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Title
A field evaluation of the effectiveness of distance sampling and double independent observers to estimate detection probability in aural avian point counts
Description
The time-of-detection method for aural avian point counts is a new method of estimating abundance, allowing for uncertain probability of detection. The method has been specifically designed to allow for variation in singing rates of birds. It involves dividing the time interval of the point count into several subintervals and recording the detection history of the subintervals when each bird sings. The method can be viewed as generating data equivalent to closed capture–recapture information. The method is different from the distance and multiple-observer methods in that it is not required that all the birds sing during the point count. As this method is new and there is some concern as to how well individual birds can be followed, we carried out a field test of the method using simulated known populations of singing birds, using a laptop computer to send signals to audio stations distributed around a point. The system mimics actual aural avian point counts, but also allows us to know the size and spatial distribution of the populations we are sampling. Fifty 8-min point counts (broken into four 2-min intervals) using eight species of birds were simulated. Singing rate of an individual bird of a species was simulated following a Markovian process (singing bouts followed by periods of silence), which we felt was more realistic than a truly random process. The main emphasis of our paper is to compare results from species singing at (high and low) homogenous rates per interval with those singing at (high and low) heterogeneous rates. Population size was estimated accurately for the species simulated, with a high homogeneous probability of singing. Populations of simulated species with lower but homogeneous singing probabilities were somewhat underestimated. Populations of species simulated with heterogeneous singing probabilities were substantially underestimated. Underestimation was caused by both the very low detection probabilities of all distant individuals and by individuals with low singing rates also having very low detection probabilities.
Bibliographic Citation
Alldredge, M. W., T. R. Simons, K. H. Pollock, and K. Pacifici. 2007. A field evaluation of the effectiveness of distance sampling and double independent observers to estimate detection probability in aural avian point counts. Avian Conservation and Ecology - Écologie et conservation des oiseaux 2:13. http://www.ace-eco.org/vol2/iss2/art13/
Creator
Alldredge, Mathew W.
Simons, Theodore R.
Pollock, Kenneth H.
Pacifici, Krishna
Subject
Aural detections
Availability process
Avian point counts
Detection probability
Field tests
Perception process
Time-of-detection method
Extent
12 pages
Date Created
2007
Type
Article
Format
application/pdf
Language
English; French (abstract only)
Is Part Of
Avian Conservation and Ecology - Écologie et conservation des oiseaux
Collection
Citation
Alldredge, Mathew W. et al., “A field evaluation of the effectiveness of distance sampling and double independent observers to estimate detection probability in aural avian point counts,” CPW Digital Collections, accessed November 26, 2024, https://cpw.cvlcollections.org/items/show/82.