Citizen science: using birder lists to detect species decline

Image credit, Gavatron.Researchers have tested a method for using species lists collected by volunteer birders to detect avian population changes. This gets at the important issue of whether we can harness citizen science from birders and other outdoor recreationists to contribute useful data to species conservation efforts.

In the case of birds, measuring changes in species abundance has typically required systematic, rigorous data collection, which can be expensive. Therefore the need for useful data presents a big challenge for conservation given our finite resources.

Meanwhile birding lists from recreational or organized volunteer efforts are common across much of the world and can cover long time periods and large geographic areas. Unfortunately, given the lack of a systematic approach in these volunteer birding efforts, scientists have largely considered this data useless for estimating changes in species abundance.

In this new study, Judit Szabo and fellow researchers address a key limitation of birding species lists - the amount of effort spent by the birder in compiling the list is usually uncontrolled and unknown.

To help get around this problem, the researchers tested a method that uses the length of a birder's species list as a surrogate for the amount of effort undertaken. Specifically, the method looks at changes in the occurrence of species relative to the length of lists to detect increases or decreases in abundance over time.

They tested their method on species lists collected by a local bird club over the course of 40 years around Brisbane in southeast Queensland, Australia. They looked at 269 bird species and were able to estimate the likelihood and magnitude of increases and declines. The species which the study determined to be declining largely mirrored what has been reported in other parts of the country.

The study uses Bayesian statistical methods to build on past work by Donald Franklin in developing the innovative approach for list-length analysis. Published in Ecological Applications, Szabo and her co-authors give good detail on the methodology of using list-length analysis as well as key limitations that practitioners need to keep in mind.

For example the method is based on the assumption that species detection probabilities are not changing systematically over time, which may not hold in some cases. Despite some of the limitations of the approach, the list-length analysis methodology presents an important step forward in using volunteer birders as citizen scientists to address species conservation data needs.

--Reviewed by Rob Goldstein

Szabo, J., Vesk, P., Baxter, P., & Possingham, H. (2010). Regional avian species declines estimated from volunteer-collected long-term data using List Length Analysis Ecological Applications DOI: 10.1890/09-0877