Geology topics
A.J. Nault
Publications and source records attributed to A.J. Nault.
Environmental contaminants in redheads wintering in coastal Louisiana and Texas
Whole body and liver analyses indicated that wintering redheads (Aythya americana; n = 70) in coastal Louisiana (one site) and Texas (two sites) were relatively free of contamination with common trace elements, organochlorines, and hydrocarbons. Most trace elements, including As, Cr, Hg, Mg, Mn, Ni, Pb, Se, Sr, and Zn, were within background concentrations in livers; levels of B, Cd, Cu, and Fe were elevated in some specimens. Only one organochlorine, DDE, was detected in redhead carcasses, but its concentration was below reported toxic levels in waterfowl. Body burdens of aliphatic and aromatic hydrocarbons were generally low, but levels of pristane, total hydrocarbons, and the ratios of phytane:n-octadecane and pristane:n-heptadecane were indicative of possible chronic exposure to petroleum. Based on brain cholinesterase assays, redheads were not recently exposed to organophosphorous or carbamate pesticides. Of 30 elements or compounds tested for seasonal differences, only Se increased from early to late winter at one of the three sites. Eight of 57 contaminants differed among the three sites; no sex or age differences were found.
Diet differences in Redheads from nearshore and offshore zones in Louisiana
Habitat management decisions for diving ducks in winter are limited by the lack of information concerning their use of nearshore and offshore zones. Therefore, we compared diets of redheads ( Aythya americana ) collected from nearshore (n = 206) and offshore (n = 72) zones during winters at the Chandeleur Islands, Louisiana, 1987-89. A greater (P < 0.05) proportion of redheads from nearshore had food in their esophagus and proventriculus than redheads from offshore. Feeding redheads in the offshore zone consumed more (P < 0.05) animal matter (42% in esophagus) and less plant material (58%) than conspecifics feeding nearshore (13% animal, 87% plant). Contents of proventriculi showed the same trend (P < 0.05). Zone-related diet differences occurred in both sexes and in early and late winter. Food availability and nutritional needs may affect these differences.