Field Notes
U.S. Fish & Wildlife Service
Field Notes Entry   
Colonial Breeding Bird Survey - Aransas National Wildlife Refuge
Southwest Region, May 24, 2007
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The annual Colonial Water Bird Survey is designed to monitor colonial bird breeding populations withing the Refute and adjacent bay systems.  This survey enables biologists to detect and track significant population shifts. 

During 2007, thirty-six islands were surveyed, twenty-six of which had active nests. A total of 2,773 nesting pairs were documented, slightly down from the 2,819 pairs recorded in 2006. Significant population shifts relative to breeding pairs can be attributed to increases in great egret and laughing gull populations, and decreases in snowy egret, cattle egret, royal tern and sandwich tern populations. High tides in late May forced birds to nest on islands with greater elevations; thus, breeding activity increased on high islands and disappeared from several low islands in the system. Least terns were absent from the 2007 survey, likely due to inundation of nest sites by high tides.

Contact Info: Martin Valdez, 505-248-6599, martin_valdez@fws.gov
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