An Evaluation of Sampling Methods for White-winged Dove Surveys in Urban Areas

Texas Parks and Wildlife Department (TPWD) has used auditory call counts annually since 1949 to monitor white-winged dove (Zenaida asiatica) populations in the Lower Rio Grande Valley of Texas. Recently, white-winged doves have been expanding their distribution, and now the largest populations occur in urban areas north of their historic south Texas range. It has become necessary to develop an urban survey method to better monitor these populations. We compared two call count sampling methods for surveying white-winged doves in urban environments (i.e., transects vs. grid-points in Austin during 1999-2002 and San Antonio during 2001-2002). We also determined the percent annual population change we were able to detect for each year with the current sample size using the grid-point survey method. Estimates of white-winged dove breeding density were higher using the transect method compared to the grid method each year. Power analysis indicated that with current sample sizes in each city, we were able to detect between a 20% and 30% annual change in mean population density in both Austin and San Antonio. We conclude the grid method can be more effective at reflecting the spatial distribution of white-winged doves in urban areas than the original transect approach. The grid method should be improved to reduce variance if it is to be used in the future. Accuracy of survey methods were not evaluated here. To obtain more reliable estimates of density, other methods such as distance sampling should be evaluated.

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