Evaluation of an aerial survey to estimate abundance of wintering ducks in Mississippi

Journal of Wildlife Management
By: , and 



Researchers have successfully designed aerial surveys that provided precise estimates of wintering populations of ducks over large physiographic regions, yet few conservation agencies have adopted these probability-based sampling designs for their surveys. We designed and evaluated an aerial survey to estimate abundance of wintering mallards {Anas platyrhynchos), dabbling ducks (tribe Anatini) other than mallards, diving ducks (tribes Aythini, Mergini, and Oxyurini), and total ducks in western Mississippi, USA. We used design-based sampling of fixed width transects to estimate population indices (I??), and we used model-based methods to correct population indices for visibility bias and estimate population abundance (N??) for 14 surveys during winters 2002-2004. Correcting for bias increased estimates of mallards, other dabbling ducks, and diving ducks by an average of 40-48% among all surveys and contributed 48-61% of the estimated variance of N??. However, mean-squared errors were consistently less for N?? than I??. Estimates of N?? met our goals for precision (CV ??? 15%) in 7 of 14 surveys for mallards, 5 surveys for other dabbling ducks, no surveys for diving ducks, and 10 surveys for total ducks. Generally, we estimated more mallards and other dabbling ducks in mid- and late winter (Jan-Feb) than early winter (Nov-Dec) and determined that population indices from the late 1980s were nearly 3 times greater than those from our study. We developed a method to display relative densities of ducks spatially as an additional application of survey data. Our study advanced methods of estimating abundance of wintering waterfowl, and we recommend this design for continued monitoring of wintering ducks in western Mississippi and similar physiographic regions.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Evaluation of an aerial survey to estimate abundance of wintering ducks in Mississippi
Series title Journal of Wildlife Management
DOI 10.2193/2007-471
Volume 72
Issue 6
Year Published 2008
Language English
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Journal of Wildlife Management
First page 1413
Last page 1419