The Texas coast serves as a major nesting area for a number of species of colonial waterbirds. As the name implies, colonial waterbirds require aquatic habitat to complete their life cycle. Observers have noted 139 bird species associated with Galveston Bay wetlands and open-bay habitats alone. Colonial waterbirds utilize the Texas coast as a nursery area and rely upon plentiful nesting habitat and food supply. They nest in colonies that range in size from just a few birds to thousands of nesting pairs. The nesting season along the Texas coast occurs annually from February thru August. Colonial waterbirds forage in various habitats including: open water, mud flats, emergent salt marshes, seagrass beds, and nesting islands. Colonial waterbirds can also be found feeding along the shores of local bayous, forested riparian areas, and inland freshwater wetlands. Colonial waterbirds' reproductive success is dependent upon the availability of suitable habitat which is free from disturbance. The following have negative impacts on colonial waterbird nesting populations along the Texas coast:
- Human disturbance of nesting sites, especially during nesting season
- Habitat loss: Erosion of nesting islands due to dredging, wakes, and loss of shoreline vegetation, Subsidence of nesting habitat and conversion to open water, and Habitat conversion and subsequent loss of foraging habitat
Mortality of colonial waterbird hatchlings due to predation by red-imported fire ants and other animals
Colonial waterbirds are an important indicator of coastal ecosystem health. Many bird species observed on the Texas Coast are predators on fish, shellfish, or benthic organisms, and therefore are important indicators of the health of coastal food webs. Trends in nesting populations are also representative of the health of vital coastal habitats. Data describing colonial waterbird populations for the Texas coast are collected by volunteers and are maintained by the U.S. Fish and Wildlife Service through the Texas Colonial Waterbird Census. The survey is done annually and attempts to count all of the nesting pairs in all of the colonies along the Texas coast. The survey excludes waterfowl and solitary nesters, such as osprey and kingfishers, but includes the herons, egrets, gulls, terns, ibises, etc. The Texas Colonial Waterbird Census is one of the most complete and long term data sets available, describing nesting populations for the years 1973-2006. HARC used the raw data to develop summary analyses and visualization of the data for the entire Texas Coast.
Open-Water and Marsh Feeders
For the purposes of this analysis, the colonial-nesting waterbirds marsh feeder guild includes: the black-crowned night heron, great blue heron, roseate spoonbill, snowy egret, tricolored heron, white ibis, white-faced ibis, and the reddish egret. The colonial-nesting waterbirds open-water feeder guild includes: the brown pelican, black skimmer, least tern, royal tern, and the sandwich tern. All species of colonial-nesting waterbirds rely on the coastal interface between land and sea for forage and nesting habitat. Open-water feeders hunt in the open waters of coastal bay systems. Marsh feeders forage mainly by wading or standing still in the water, searching for their prey in fresh or brackish wetlands. Most species of colonial-nesting waterbirds nest in trees or directly on the ground on small bay islands, beaches, or other suitable habitat. It is important to analyze population data for colonial-nesting waterbirds according to feeding guild and nesting habits as well as by species to examine any trends that would indicate loss or compromise of necessary habitat.