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Factors affecting visibility rate of aerial waterfowl surveys in the Mississippi alluvial valley

Journal of Wildlife Management

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Abstract

Because visibility bias can confound attempts to detect changes in abundance, we evaluated factors that affect visibility rate in aerial surveys of wintering waterfowl. We placed waterfowl decoys in 32 2- x 0.25-kin strip transects in the Mississippi Alluvial Valley (MAV) during February 1990 and 1991 and observed the decoys under different experimental conditions. Visibility rate was influenced (P 0.10) by habitat, transect width, and decoy group size. We simulated variation in use of habitat and found that changes in use between open and wooded wetlands would cause changes in visibility rate and affect the power to detect a change in abundance. The effect of changes in visibility rate on likelihood of detecting population change depended on the magnitude and direction of population change and precision of the population index. For transect surveys of wintering ducks in the MAV we recommend reducing transect width from 250 to 150 m on each side of the aircraft and restricting comparisons between years when 70% of the population is likely to be distributed in open wetlands. Improved techniques for estimating abundance of wintering waterfowl are also needed so use of questionable population indices can be avoided.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Factors affecting visibility rate of aerial waterfowl surveys in the Mississippi alluvial valley
Series title:
Journal of Wildlife Management
Volume
59
Issue:
3
Year Published:
1995
Language:
English
Contributing office(s):
Patuxent Wildlife Research Center
Description:
515-527
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
515
Last page:
527
Number of Pages:
13