Status and recent trends of Galveston Bay's colonial water birds with management implications

Approximately 66 species belonging to the group popularly called water birds are known to regularly occur in Galveston Bay and its adjacent wetlands. These are the migrant waterfowl (approximately 31 species), regularly nesting waterfowl (2 species), migrant fish-eating birds (10 species), and colonial water birds (23 species). These numbers do not include vagrants or accidentals which irregularly occur along the upper Texas coast, the group (37 species) called shorebirds belonging to the plover and sandpiper families, or about 11 species of rails, cranes, the wood stork, and smaller wading birds generally considered aquatic but which do not fit into the above categories. Nor do they include wide-ranging pelagic birds which do not regularly breed on the Texas coast. The 23-species subgroup called colonial water birds is composed of gulls, terns, skimmers, herons, egrets, cormorants, and pelicans. This subgroup lends itself to regular censusing because its members annually aggregate during the breeding season in large, well-defined, and easily censused colony sites. Primarily fish and aquatic invertebrate-eating birds, these birds are ideal to serve as monitors because they are resident and widespread over most of the bay for most of the year and they occupy higher levels of the food chain. also they are susceptible to many of the factors affecting the bay ecosystem, such as fluctuations in populations of forage species, invasions of exotic pest species, human disturbance, erosion of intertidal and shoreline habitat, chemical contamination, and extreme climatic conditions. We believe that accurate and long-term counts of colonial water birds can be a sensitive tool to detect important biological changes to the estuary.