Gulf Coast Gadwall Study
Regional and Long-Range Movements of Female Gadwalls along the Gulf Coast
Over 75% of the continental gadwall population winters in coastal marshes along the Louisiana and Texas Gulf Coast, along with substantial proportions of several other species of waterfowl, including northern pintails, American wigeon, green-winged and blue-winged teal, and lesser scaup. Consequently, the North American Waterfowl Management Plan through the Gulf Coast Joint Venture (GCJV), and Ducks Unlimited through its International Conservation Plan, place top priority on conservation of winter and migration habitat in this region.
Despite the apparent importance of coastal marshes to wintering gadwalls, winter ecology of this species is poorly understood. Paulus (1982, 1983, 1984) studied feeding ecology, gut morphology, pairing chronology, dominance relationships, molt, and time-activity budgets of gadwalls wintering in coastal Louisiana. He reported that gadwalls spent about 64% of each 24-hour period feeding on a diet that consisted of approximately 95% submerged aquatic vegetation. This preference for submerged aquatic vegetation suggests a heavy reliance on coastal marsh habitats, but habitat use of wintering gadwalls has not been well studied.
The extent, timing, and frequency of regional and long-range movements are also unknown. Because gadwalls spend extensive time feeding, disturbance may be an important factor influencing choice of wintering areas, regional movements, and over-winter survival rates.
Anecdotal observations of waterfowl suggest that winter distributions of gadwall may have changed recently. The Gulf Coast region has experienced relatively poor duck hunting during recent years. Gadwalls typically are the most frequently harvested species in Louisiana and Texas. Hence, there is considerable interest from the waterfowl management community and hunters in understanding the relative roles of hunting, sanctuary, weather, and public and private habitat conservation programs in affecting movements of wintering gadwalls.
This study will seek to answer questions about regional and long-range movements of gadwall wintering on the Gulf Coast, and the influence of weather, and hunting pressure on such movements. Additionally, this study will estimate over-winter survival rates and determine habitat use on public and private lands.
Finally, considerable speculation exists concerning movements of gadwall among such regions as the southern brushlands, rice prairies, and coastal marshes of Texas; rice prairies, major river deltas, and other marshes of Louisiana; and other regions of the southern U.S. and Mexico. Changes in habitat conditions or other factors such as hunting pressure may play a role in inter-regional movements, if they occur. Understanding of larger scale movements would be helpful to conservation planners, habitat managers, and waterfowl hunters. Strategic changes to conservation and management plans may be warranted if data suggest that plans are not properly aligned spatially and temporally with bird movements and/or patterns of habitat use.