Habitat use, movements, and ecology of female mottled ducks on the Gulf Coast of Louisiana and Texas

Abstract

Mottled ducks (Anas fulvigula) are the most abundant breeding waterfowl in the coastal marshes of Louisiana and Texas. Mottled ducks are non-migratory and heavily dependent on coastal marsh habitats; they must satisfy all of their annual resource needs from within the Gulf Coast region. Coastal marsh habitats are being rapidly lost or degraded in Louisiana and Texas. The hydrology of many coastal marsh habitats has been altered by anthropogenic activity and natural factors. Parameters related to Mottled Duck habitat use and movements in this altered environment are poorly understood, and managers need information on vital rates of Mottled Ducks in coastal Louisiana and Texas. Information on use of habitats, breeding pair densities, and movements of female Mottled Ducks could benefit managers charged with conservation of Mottled Ducks and coastal marsh habitats and be used to guide resource allocation for restoration and conservation in this region. Additionally, information on breeding propensity would satisfy a need to establish vital rates used for population modeling. I employed radio-telemetry techniques to evaluate use of habitats and movements by female Mottled Ducks in the Gulf Coast region. I used a transect survey as an index to pair densities in different habitats, and evaluated examination of postovulatory follicles as a method to assess breeding propensity in Mottled Ducks. Mottled Ducks used fresh and intermediate marsh heavily and pair densities were greatest in fresh marsh habitats. Mottled ducks had low movement distances and moved inland away from storm surge caused by hurricanes. Macroscopic examination of postovulatory follicles was not appropriate for evaluation of breeding propensity in Mottled Ducks. Conservation of natural coastal marsh habitats in Louisiana and Texas will benefit Mottled Ducks in the Western Gulf Coast region.