Abundance of Snowy and Wilson's plovers in the lower Laguna Madre region of Texas

Abstract

Snowy Plovers (Charadrius alexandrinus) and Wilson's Plovers (C. wilsonia) are shorebird species of increasing conservation concern, with populations apparently declining in North America. However, estimates of current populations are needed before initiating long-term monitoring or planning. In 2004, we estimated abundance of breeding Snowy and Wilson's plovers in the lower Laguna Madre region of Texas using occupancy abundance estimation. We made repeated visits to survey plots from April to June, recording the number of adults of both species observed and the amount of suitable breeding habitat within each plot. We considered Bayesian occupancy abundance models with and without habitat covariates to explain the abundance of both species. For both Snowy and Wilson's plovers, the number of birds counted in each plot was influenced by the amount of suitable breeding habitat within the plot (Snowy Plover αhabitat = 0.52, SD = 0.10, 95% CI = 0.33-0.71; Wilson's Plover αhabitat = 0.48, SD = 0.12, 95% CI = 0.24-0.71). Using the habitat covariate models for each species, we estimated that 416 adult Snowy Plovers (95% CI = 394-438) and 279 adult Wilson's Plovers (95% CI = 262-296) were present in our study area. Our results illustrate the use of a relatively new method for abundance estimation, and indicate that the lower Laguna Madre region of Texas is an important breeding area for both Snowy and Wilson's plovers. Given the documented and suspected population declines for Snowy and Wilson's plovers, we recommend protection of their breeding habitats along the coast of Texas from development and degradation resulting from unregulated use. © 2007 Association of Field Ornithologists.