Population Density and Habitat Associations of the Seaside Sparrow on Laguna Atascosa National Wildlife Refuge, Cameron County, TX
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In 2000, a resident population of Texas Seaside Sparrows (Ammodramus maritimus) was identified at Laguna Atascosa National Wildlife Refuge on the lower Texas coast, extending its known breeding distribution further south than previously described. I studied this breeding population of Texas Seaside Sparrows on the Laguna Atascosa National Wildlife Refuge to obtain population density estimates and describe habitat associations. I estimated seasonal density during one year using a distance sampling approach. I identified plant species and estimated percent ground cover using a 20x50 cm frame placed systematically along bird survey transects.
Seaside Sparrow density estimates by season were 3.49/ha (CV = 8.27) for spring 3.59/ha (CV = 18.16) for summer, 4.07/ha (CV = 9.69) for fall, and 1.91/ha (CV = 21.92) for winter. The dominant plant species along the intertidal zone transect where Seaside Sparrows were detected include Saltwort (Batis maritima), Saltgrass (Distichlis spicata), and Sea oxeye daisy (Borrichia frutescens). Previous studies indicated cordgrasses (Spartina spp.) to be a dominant plant species strongly associated with Seaside Sparrows and a predictor of nest success. However cordgrasses were absent from the intertidal zone where Seaside Sparrows were detected during my study. Habitat associations should be revised to include the plant community found in this study.