Characteristics of Ponds Used by Breeding Mottled Ducks on the Chenier Plain of the Texas Gulf Coast

Abstract

Abstract Mottled ducks Anas fulvigula are nonmigratory and primarily depend on habitats associated with coastal marshes of the Gulf Coast for their entire life cycle. Much of remaining available coastal marsh habitats of the Texas Gulf Coast are managed by state and federal agencies. The Texas Gulf Coast breeding population of mottled ducks has recently declined dramatically. To aid in development of management plans for breeding mottled ducks, we estimated the number of potential pair ponds available on the Texas Chenier Plain National Wildlife Refuge Complex relative to marsh type (fresh, intermediate, brackish, and saline), estimated occupancy, compared habitats of used and unused pair ponds, and evaluated pair pond selection relative to marsh type during spring 2004 and 2005. Greater than 18,000 ponds were recorded in >22,400 ha of coastal marsh with >74% of potential pair ponds in the intermediate marsh type. Average pond size of 425 randomly selected ponds across marsh types was 0.09 ha. Pond occupancy was estimated as 1.3% and 2.5% in 2004 and 2005, respectively, in 634 ponds surveyed for presence of mottled duck pairs. Mottled ducks selected for ponds in fresh marsh with short surrounding vegetation associated with recent cattle grazing, but avoided recently (<3 mo prior) burned areas. Pond area was greater with shallower water depth for used compared to unused ponds. The presence and coverage of submergent and emergent vegetation did not influence use of pair ponds by mottled ducks. Development of breeding habitat (pair ponds, nesting cover, brood habitat) in fresh marsh will benefit mottled ducks. Our results indicate development of breeding habitat on the Texas Gulf Coast, and vegetation management using cattle grazing timed for disturbance in fresh marsh during mid- to late winter and early spring will further attract breeding mottled ducks.