Organochlorine contaminants and reproductive success of black skimmers in south Texas, 1984

Ninety-four Black Skimmer (Rhynchops niger) nests on a dredged-material island colony near Laguna Vista, Texas, were fenced and monitored in 1984 from early incubation until 21 d after the last egg hatched. The daily probability of success was greater during the nestling (99.7%/d/nest) period than during the incubation (98.5%) or hatching (98.5%) periods. By contrast, the success of eggs or young in successful nests was greater during the incubation (91.3%) and hatching (84.3%) periods than the nestling period (63.8%). An estimated 1.1 young/nest survived to 21 d of age. DDE concentrations in eggs were lower in 1984 than in eggs from the same colony in 1979-1981. DDE was higher in eggs taken from nests where none of the remaining eggs hatched (x̄ = 5.9 ppm) compared to eggs taken from nests where all the remaining eggs hatched (x̄ = 1.9 ppm).