Ecology of a restored wetland in the Trinity River floodplain of Texas.

摘要

I examined bird use and ecology of pasture converted to a wetland cell complex with water management capability. Ducks (Anatidae) and wading birds (Ciconiiformes) were the dominant birds during winter and summer, respectively. Avian community similarity (after Schoener 1968) did not correlate with habitat similarity (from principal components score plots) in both winter and summer. This result has implications for those who use birds as an index of restoration success. This result also suggests that interspecific competition does not drive the structuring of wetland avian communities. This may relate either to the absence of resource limitation, or to the absence of niche partitioning due to generalism. Alternatively, this result may reveal the inadequacy of this method for detecting the influence of habitat variation on avian community structuring. In regression analyses, only area significantly (P 0.05) predicted bird species richness (BSR) during the first winter, this result was not duplicated in the second winter validation model. Benthic invertebrate (BINV) taxa richness and crayfish biomass significantly (P 0.05) predicted bird species diversity (BSD) in summer 1997. This model was not subjected to validation procedure, however. BSR and BSD declined from the first to second winter (P 0.05), however MANOVA suggested no change in the avian community. Conversely, MANOVA suggested change in both limnetic invertebrate (LINV) and plant communities during the same period. Crayfish abundance increased significantly during the second winter (P 0.05). Light, continuous summer grazing (1 AU/ha) had no effect on BSR or BSD. Likewise, grazing did not affect algae production, percent vegetative cover, or moist soils plant height and seed-bearing stem density. A nearby, older comparison wetland had higher mean LINV taxa richness (P .05), while the new wetland had higher mean BINV taxa diversity and biomass (both P .05). Water in the study area impoundments had lower turbidity, specific conductance, NO3=, and PO 43- than Trinity River source water (P .05). Dense submerged vegetation is conducive to high invertebrate production, which may be the key to providing adequate food resources for water birds at this site. Careful water management may preserve the grass substrate, thereby optimizing benefits to cattle and water birds.