An aerial grid‐based sampling method to estimate nonbreeding duck abundance. (4th October 2017)

• Record Type: Journal Article
• Authors: Hennig, Jacob D.; Benson, Thomas J.; Stafford, Joshua D.; Yetter, Aaron P.; Hagy, Heath M.; Stodola, Kirk W.
• Is Part Of: Wildlife Society bulletin. Volume 41:Number 4(2017)
• Page Start: 678
• Page End: 684
• Publication Date: 2017-10-04
• Subjects: discontinuous habitat -- floodplain -- Illinois -- Indiana -- Wabash River -- waterfowl; Wildlife management -- Periodicals; Wildlife conservation -- Periodicals; 333.9540973
• DOI: 10.1002/wsb.807
• Languages: English
• ISSNs: 0091-7648

Abstract

ABSTRACT: Probability‐based sampling designs for aerial surveys are useful for estimating wintering waterfowl abundances in large areas with contiguous habitat (e.g., Mississippi Alluvial Valley). The effectiveness of these approaches for estimating abundance of nonbreeding waterfowl in small areas with discontinuous habitat has rarely been assessed. Surveys conducted within riverine areas introduce sampling design difficulties because of discontinuous bottomland habitat and irregularity of flooding events. Therefore, we implemented and evaluated a generalizable grid‐based, stratified random sampling design to estimate weekly duck abundance within the Wabash River floodplain in southeastern Illinois and southwestern Indiana, USA, during midwinter and early spring 2012 and 2013. We used aerial and ground‐based counts to generate abundance estimates and evaluate within‐week variation of counts. Peak duck abundance totaled 279, 717 (SE = 69, 101) in 2012 and 742, 027 (SE = 296, 563) in 2013. Dabbling ducks were the most abundant duck guild detected and abundance estimates for this group met our precision goal (CV ≤ 0.25) in 4 of 18 surveys ( x ¯ = 0.33, range = 0.20–0.51). We compared the grid‐based approach with a traditional aerial inventory and found that estimates from the grid‐based approach were on average 75, 175 (SE = 46, 768) greater than inventory counts. Desired levels of precision were often not met, yet design improvements in 2013 notably increased precision, suggesting that further modifications may allow this method to be useful in riverine areas with discontinuous and ephemeral habitat. © 2017 The Wildlife Society. Abstract : We implemented and evaluated a generalizable grid‐based, stratified random sampling design to estimate non‐breeding duck abundance in a riverine area containing discontinuous and ephemeral habitat, and compared it to a traditional aerial inventory. Precision goals were not often met for our grid‐based design, but we found that abundance estimates were on average 75, 175 (SE = 46, 768) greater than inventory counts.