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

1987; Association of Field Ornithologists; Volume: 58; Issue: 4 Linguagem: Inglês

1557-9263

Thomas W. Custer, Christine A. Mitchell,

Environmental Toxicology and Ecotoxicology

-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 (x = 5.9 ppm) compared to eggs taken from nests where all the remaining eggs hatched (x = 1.9 ppm). CONTAMINANTES ORGANOCLORINADOS Y EL EXITO REPRODUCTIVO DE RHYNCHOPS NIGER DURANTE EL 1984 EN EL SUR DE TEXAS Sinopsis.-Durante el 1984 se estudi6 una colonia de rayadores de agua (Rhynchops niger) cerca de Laguna Vista, Texas. Noventa y cuatro nidos fueron monitoreados desde comienzos del periodo de incubaci6n hasta 21 dias despu6s de los huevos haber eclosionado. La probabilidad diaria de exito de nidos fue mayor durante la epoca de presencia de polluelos (99.7%/ d/nido) que durante las epocas de incubaci6n (98.5%) o de eclosionamiento (98.5%). Por el contrario el exito de huevos o crias en nidos exitosos fue mayor durante la incubaci6n (91.3%) y eclosionamiento (84.3%) que durante el periodo de polluelos. Un estamado de 1.1 polluelos/nido sobrevivieron hasta la edad de 21 dias. La concentraci6n de DDE en huevos result6 ser menor en 1984 que en analisis similar sobre la colonia en 1979-1981. La cantidad de DDE result6 mayor en huevos tomado de nidos en donde ninguno de los restantes eclosion6 (x = 5.9 ppm), que en huevos en donde el remanente de la camada produjo pichones (x = 1.9 ppm). Populations of breeding Black Skimmers (Rynchops niger) declined 24% from 11,540 to 8760 breeding pairs between 1974 and 1980 (Texas Colonial Waterbird Society 1982). A study of skimmers at three Texas colonies in 1978-1981 (White et al. 1984) found that DDE concentrations in eggs were high, and were not correlated with eggshell thickness. DDE concentrations in eggs and fledging success on a colony basis were not related; a relationship, however, could have been hidden by other variables that affect nest success such as storm tides (Blus and Stafford 1980, Burger 1982, King and Krynitsky 1986, White et al. 1984), starvation (Erwin 1977), or predation (Blus and Stafford 1980, Burger 1982, DePue 1974, King and Krynitsky 1986). DDE concentrations and hatching success were not compared, because young could not be assigned to specific nests. I Mailing address: Gulf Coast Field Station, P.O. Box 2506, Victoria, Texas 77902 USA. 2 Mailing address: LSU-School of Forestry, Wildlife and Fisheries, Baton Rouge, Louisiana 70803 USA.