The City of San Marcos released new maps that clearly show the trails and areas that are closed from March 1 to May 31, 2013 to protect the nesting golden-cheeked warbler. From the City of San Marcos web site:
The golden-cheeked warbler is an endangered species of bird that breeds only in central Texas and nests in the Ashe-juniper and oak found in some of our natural areas. In an effort to protect these rare birds certain trails in Purgatory Creek Natural Area and Spring Lake Natural Area will be closed from March 1-May 31 annually.
Click here for maps of the closed areas.