A comparison of bird use and species diversity of created and natural salt marshes in the Galveston Bay complex, Texas

Abstract

Birds were censused in seven natural and seven created salt marshes in lower Galveston Bay from October 1990 through September 1991 to evaluate differences in bird use due to marsh origin, size, and age. Birds were grouped by foraging method, prey items, habitat use, and season they are present in Galveston. Six common marsh species were analyzed separately. Bird use was tested for relationships with vegetation characteristics, habitat components, and distance to active colonies. Bird use of created and natural marshes differed significantly, however not consistently. Bird abundance was greater in created than natural salt marshes. Young created salt marshes supported more birds than natural or old created marshes. Gulls and tems occurred more in young created marshes than either older created or natural marshes. Natural marshes supported more rails and shorebirds than created marshes. Sparrows were more abundant in natural than young created marshes. Winter residents used natural marshes more than created marshes. Year round residents were more abundant in created marshes. Abundance of miscellaneous species, shorebirds, sparrows and all residence categories was positively related to amount of vegetated marsh habitat and marsh size. Bay habitat was positively related to number of summer, winter, and year round residents. Bird abundance was directly related to plant height. Year round species were positively related and waterfowl numbers negatively related to fall plant height. Gulls and tems were positively related to spring height. Abundance of year round species and gulls and tems was positively related to plant density in the inner marsh during spring. Location of active colonies < 2.43 km away increased marsh use by some colonial waterbirds. Species diversity was greater in natural than created marshes. Marsh size and presence of all habitat types were directly correlated to higher species diversity within the marsh. Number of habitats within each sample site was directly related to species diversity. This study indicates that bird use is influenced by marsh size, habitat types within marshes, distance to bird colonies, and height and density of plants in marshes. Since created marshes differed in some of these characteristics, bird utilization also differed.