Colonial Waterbirds in Galveston Bay

Galveston Bay serves as a major nesting area for many species of colonial waterbirds. As the name implies, colonial waterbirds require aquatic habitat to complete their life cycle. Colonial waterbirds rely upon a plentiful food supply found in the open bay, mud flats, emergent salt marshes, and seagrass beds. They can also be found feeding along the shores of local bayous, riparian forests (forests near the banks of bayous and streams), and emergent freshwater wetlands.

Colonial waterbirds nest in colonies that range in size from just a few to thousands of nesting pairs. Nesting sites are often in remote areas such as bird islands, isolated stretches of beach, and dense wetlands. This helps to protect breeding adults and fledglings from predators and human disturbance. The nesting season in Galveston Bay is February through August.

The reproductive success of colonial waterbirds is dependent upon the availability of suitable habitat free from disturbance. The following have negative impacts on colonial waterbird populations in Galveston Bay:

• Human disturbance of nesting sites, especially during nesting season
• Habitat loss:
  • Erosion of nesting islands due to dredging, vessel wakes, and loss of  shoreline vegetation
  • Subsidence of nesting habitat and conversion to open water
  • Conversion and loss of foraging habitat
• Mortality of colonial waterbird hatchlings due to predation by red-imported fire ants and other animals.

About the Data
Data describing colonial waterbird populations for the Texas coast are collected by volunteers on an annual basis and are maintained by the U.S. Fish and Wildlife Service Texas Colonial Waterbird Census. In 2006, the Galveston Bay Status and Trends Project analyzed the data for trends in colonial waterbird populations. The database reported nesting pair abundance for 30 species of colonial waterbirds observed at 131 nesting colonies in Galveston Bay during the years 1973-2005.

Population Trend Indicator
The indicator below shows the twenty year trends in population abundance for 15 species of colonial waterbirds (eight marsh feeding and seven open water feeding species).

Note: A trend is considered significant if the R² value is .25 or greater. An R² of .25 means that the trend line explains 25% of the variation in the data. The closer the R² is to 1, the stronger the trend

Click on the species name to view the twenty-year population trend.

Feeding Habitat Species 20 Year Trend (1986-2005) Marsh Black-crowned Night Heron   Great Blue Heron   Reddish Egret   Roseate Spoonbill   Snowy Egret   Tri-colored Heron   White Ibis   White-Faced Ibis   Open Water Black Skimmer   Brown Pelican   Laughing Gull   Least Tern   Neotropic Cormorant   Royal Tern   Sandwich Tern

Visit these sites for more information about colonial waterbirds:

• US Fish and Wildlife Service - Texas Coastal Program
• Great Texas Coastal Birding Trail
• Houston Audubon
• Audubon Texas
• Waterbird Conservation for the Americas