Bird Point Count CV Tool


Patuxent Wildlife Research Center	Managers' Monitoring Manual

Managers' Monitoring Manual > CV Tools > Bird Point Count CV Tool

Coefficients of Variation Tool for Point Counts of North American Birds from Breeding Bird Survey routes

Select species Search by Latin name
Select state/province (U.S./Canada only)	(optional)
Select stratum (U.S./Canada only)	(optional)
Stops
Select minimum length of time series	(from 4 to 36)

	The more you narrow down your search above, the fewer corresponding records the database will return. Screening too far may result in zero records returned. Searches returning a large number (i.e. thousands) of records may take a few seconds or more to display.

This dataset is a subset of the Breeding Bird Survey database.

To minimize the impact of observers on calculations of the CV's (coefficients of variation), we determined the observer with the longest run of years for a particular route, and only used data from that observer. If no observer had 4 or more years of data for a particular route, we did not include that route in this dataset. From the single-observer time series data for a particular route, we calculated the CV and stored it in a database. Data are available from a total of 4974 routes, yielding 301342 count series for 646 bird species.

The CV is calculated by running a linear regression of the time series data (where time is the independent variable and count is the dependent variable), taking the standard deviation of the residuals and dividing it by the mean of the counts. See an example of how the CV is calculated.

The purpose of this web site is to provide estimates of the year-to-year variability of avian point count indices of 5 combinations of stops (10, 20, 30, 40, 50) and for the frequency of stops on which a bird was found (stops per species). Those estimates of variation can be used in power and sample size calculations to calculate sample sizes for proposed studies using point counts.