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C. A. Mitchell

Publications and source records attributed to C. A. Mitchell.

At least 19 recordsLinked to original sources
USGS2020

Monocrotophos and dicrotophos residues in birds as a result of misuse of organophosphates in Matagorda county Texas USA

About 1100 birds of 12 spp. [Red-winged blackbird ( Agelaius phoeniceus ), great-tailed grackle ( Quiscalus mexicanus ), brown-headed cowbird ( Molothrus ater ), mourning dove ( Zenaida macrours ), Eastern meadowlark ( Sturnella magna ), vesper sparrow ( Pooecetes gramineus ), common snipe ( Gallinago gallinago ), blue-winged teal ( Anas discors ), mottled duck ( Anas fulvigula ), common moorhen ( Gallinula chloropus ), redhead ( Aythya americana ) and ruddy turnstone ( Arenaria interpres )] died from organophosphate poisoning in Matagorda County on the Texas Gulf Coast in March and May 1982. Birds died from feeding on rice seed that was illegally treated with dicrotophos or monocrotophos and placed near rice fields as bait to attract and kill birds. Brain acetylcholinesterase inhibition of affected birds averaged 87% (range 82-89%), and contents of gastrointestinal tracts contained residues of dicrotophos (5.6-14 ppm) or monocrotophos (2.1-13 ppm). Rice seed collected at mortality sites contained 210 ppm dicrotophos or 950 ppm monocrotophos. Mortality from dicrotophos poisoning continued for almost 3 wk. The practice of illegally treating rice seed with either of the 2 organophosphates appears to be infrequent but widespread at present.

Texas↗
USGS1994

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.

Louisiana, Texas↗
USGS1993

Trace elements and organochlorines in the shoalgrass community of the lower Laguna Madre Texas

Our objectives were to measure concentrations of seven trace elements and 14 organochlorine compounds in sediment and biota of the shoalgrass ( Halodule wrightii ) community of the lower Laguna Madre of south Texas and to determine whether chemicals associated with agriculture (e.g. mercury, arsenic, selenium, organochlorine pesticides) were highest near agricultural drainages. Arsenic, mercury, selenium, lead, cadmium, and organochlorines were generally at background concentrations throughout the lower Laguna Madre. Nickel and chromium concentrations were exceptionally high in shrimp and pinfish ( Lagodon rhomboides ), which is difficult to explain because of no known anthropogenic sources for these trace elements. For sediment and blue crabs ( Callinectes sapidus ), mercury was highest near agricultural drainages. Also, DDE was more frequently detected in blue crabs near agricultural drainages than farther away. In contrast, selenium concentrations did not differ among collecting sites and arsenic concentrations were lowest in shoalgrass, blue crabs, and brown shrimp ( Penaeus aztecus ) near agricultural drainages.

Texas↗
USGS1993

Lesser scaup forage on zebra mussels at Cook nuclear plant, Michigan

Nineteen of 21 Lesser Scaup (Aythya affinis) entrained while foraging at the water intake structures of Cook Nuclear Plant, Bridgman, Michigan had consumed zebra mussels (Dreissena polymorpha). The average number of zebra mussels in the upper gastrointestinal tract was 260; maximum number was 987. Migrating Lesser Scaup found this new food source during the first winter following settlement of zebra mussels on the water intake structures of the power plant.

Journal of Field Ornithology↗
USGS1992

Redhead duck behavior on lower Laguna Madre and adjacent ponds of southern Texas

Behavior of redheads (Aythya americana) during winter was studied on the hypersaline lower Laguna Madre and adjacent freshwater to brackish water ponds of southern Texas. On Laguna Madre, feeding (46%) and sleeping (37%) were the most common behaviors. Redheads fed more during early morning (64%) than during the rest of the day (40%); feeding activity was negatively correlated with temperature. Redheads fed more often by dipping (58%) than by tipping (25%), diving (16%), or gleaning (0.1%). Water depth was least where they fed by dipping (16 cm), greatest where diving (75 cm), and intermediate where tipping (26 cm). Feeding sequences averaged 5.3 s for dipping, 8.1 s for tipping, and 19.2 s for diving. Redheads usually were present on freshwater to brackish water ponds adjacent to Laguna Madre only during daylight hours, and use of those areas declined as winter progressed. Sleeping (75%) was the most frequent behavior at ponds, followed by preening (10%), swimming (10%), and feeding (0.4%). Because redheads fed almost exclusively on shoalgrass while dipping and tipping in shallow water and shoalgrass meadows have declined in the lower Laguna Madre, proper management of the remaining shoalgrass habitat is necessary to ensure that this area remains the major wintering area for redheads.

Southwestern Naturalist↗
USGS1991

Contaminant exposure of willets feeding in agricultural drainages of the lower Rio Grande valley of south Texas

Willets ( Catoptrophorus semipalmatus ) were collected in June and August 1986 at the outlets of two agricultural drainages into the Lower Laguna Madre of South Texas and at two other Texas coastal sites. Mean liver concentration of arsenic was higher in August than June. Over 20% of the livers had arsenic concentrations elevated above a suggested background level of 5.0 ppm dry weight (DW), but concentrations (maximum 15 ppm) were below those associated with acute toxicity. Selenium concentration in livers varied from 2.3 to 8.3 ppm DW for all locations and represented background levels. Mercury concentrations in livers for all locations (means = 2.0 to 3.4, maximum 17 ppm DW) were below those associated with avian mortality and similar to levels found in other estuarine/marine birds. DDE in carcasses was higher in adults (mean = 1.0 ppm wet weight) than juveniles (0.2 ppm), and higher in August (1.0 ppm) than June (0.5 ppm); however, DDE concentrations were generally at background levels. Based on brain cholinesterase activity, willets were not recently exposed to organophosphate pesticides.

Environmental Monitoring and Assessment↗
USGS1990

Body mass and lipid content of shorebirds overwintering on the south Texas coast

Three species of shorebirds were collected at bimonthly intervals in 1979-1980, from the time of their arrival in early autumn to mid-February, on the south Texas coast. Female Long-billed Dowitchers (Limnodromus scolopaceus) and Western Sandpipers (Calidris mauri) were heavier (P < 0.05) than males, but the reverse was true for American Avocets (Recurvirostra americana). Lipid content, relative to whole body mass, did not differ (P > 0.05) between sexes in any of the three species. During the wintering period, fat stores in Long-billed Dowitchers and Western Sandpipers declined 70% and 44%, respectively, but not in American Avocets. Lipid content was highly correlated (P < 0.001) with body mass in all three species, providing further evidence that fat accumulation is responsible for the major variation in total mass of some shorebird species.

Journal of Field Ornithology↗
USGS1989

Organochlorine contaminants in white-faced ibis eggs in southern Texas

White-faced ibis eggs collected from 2 colonies in southern Texas in 1985 had low mean concentrations of DDE. DDD, the only other organochlorine contaminant detected, was found in only 1 of 20 eggs. DDE concentrations in eggs were not significantly correlated with eggshell thickness. Mean DDE concentrations were significantly higher in eggs collected from nests where not all of the remaining eggs hatched than in eggs collected from nests where all the remaining eggs hatched.

Colonial Waterbirds↗
USGS1987

Exposure to insecticides of brushland wildlife within the Lower Rio Grande Valley, Texas, USA

Brushland wildlife within the Lower Rio Grande Valley of south Texas were studied following applications of eleven insecticides to nearby sugarcane or cotton fields. During the study no wildlife were found dead. Mean brain acetylcholinesterase (AChE) activity of great-tailed grackles ( Quiscalus mexicanus ) and mourning doves ( Zenaida macroura ) was significantly lower than controls following application of some organophosphorous insecticides. Brain AChE activity varied significantly among chemicals, days after exposure and application rates. Mean brain AChE activity of white-winged doves ( Zenaida asiatica ) and three small mammal species was not significantly different than their respective controls following application of insecticides. Mean brain AChE activity of grackles was inhibited significantly more than white-winged doves after application of Bolstar®, EPN-methyl parathion, and Azodrin® and significantly more than that of mourning doves after applications of Bolstar® and EPN-methyl parathion. Our data indicate that there were no adverse effects on most brushland wildlife. Exposure was probably dependent upon use of the agricultural fields as feeding or resting sites and only grackles and mourning doves were regularly present in the fields.

Texas↗
USGS1986

Hatching success of Caspian terns nesting in the lower Laguna Madre, Texas, USA

The average clutch size of Caspian Terns nesting in a colony in the Lower Laguna Madre near Laguna Vista, Texas, USA in 1984 was 1.9 eggs per nest. Using the Mayfield method for calculating success, one egg hatched in 84.1% of the nests and 69.8% of the eggs laid hatched. These hatching estimates are as high or higher than estimates from colonies in other areas.

Texas↗
USGS1986

Bird poisoning from misuse of the carbamate Furadan in a Texas rice field

More than 100 birds consisting largely of dickcissels and savannah sparrows, as well as 9 other species of songbirds and sandpipers, died from feeding on planted rice seed treated illegally with Furadan 4F. Brain ChE activity was depressed between 32-85% in 44% of the birds. Carbofuran residues in GI tract contents of birds averaged 3.4 ppm (0.54-10 ppm). Two samples of planted rice seed contained 91 ppm and 22 ppm carbofuran. Known mortality of birds continued for about 2 weeks.

Wildlife Society Bulletin↗
USGS1986

Dieldrin and endrin residues in fulvous whistling-ducks in Texas in 1983

Fulvous Whistling-Ducks were collected near nesting areas in the rice fields of Texas in 1983 to determine if these birds continue to carry residue levels of organochlorine contaminants, and if the contaminants were acquired in Texas or Mexico. Adults were collected immediately after they arrived from wintering grounds and juveniles were collected in late summer before their departure to wintering grounds. Carcasses of 7 of 15 adults, some of which had been feeding in rice fields, contained residues of dieldrin in low to moderately high levels and 4 contained low levels of endrin. None of 16 flightless juveniles contained organochlorine residues. The contaminated adults were most likely exposed to aldrin or dieldrin via illegal treatment of rice seed with aldrin in some nesting areas of Texas.

Journal of Field Ornithology↗
USGS1985

Organochlorine concentrations, whole body weights, and lipid content of black skimmers wintering in Mexico and in south Texas, 1983

Since 1978, a large proportion of the black skimmers (Rynchops niger) nesting along the Texas coast have had high concentrations of DDE in their eggs. Of 284 eggs collected from 5 sites during 1978-81, 99.5% contained detectable (> 0.i0 ppm) w levels of DDE, ranging up to 86 ppm wet-weight; 36% of the eggs contained > i0 ppm DDE (White et al., 1984). During the 4-year period, geometric mean concentrations of DDE remained strikingly similar, with no significant decline in egg contaminant levels. The sources of DDE contamination in skimmers are unknown. Recoveries of juvenile skimmers banded in Texas, Louisiana, and Mississippi indicate that a large proportion of the birds (60%) spend the winter on the east and west coasts of Mexico. Therefore, it is possible that the DDE exposure to Texas skimmers occurs in Mexico during the winter, although some birds remain along the Gulf Coast year-round.\ This study was conducted to determine the degree of DDE and other organochlorine contamination in black skimmers and their food items from sites in Mexico and Texas, and to statistically compare residue concentrations and body condition in individuals from the 2 areas.

Texas, Veracruz↗
USGS1984

Reproductive success of black skimmers in Texas relative to environmental pollutants

We studied the nesting ecology of Black Skimmers along the lower Texas coast during 1978-1981 to learn more of their reproductive status and to evaluate the effects of organochlorine pollutants, such as DDE, on productivity. For 542 nests, the average clutch size was 3.3 eggs. Flooding was the major cause of colony destruction and abandonment. Clutch size in renest attempts decreased significantly from that in first attempts. Overall fledging success (fledglings/total pairs) averaged 1 0 fledgling per pair. There was a significant negative correlation between number of nest attempts and fledging success on a colony basis. Also, clutch size and fledging success were significantly correlated. DDE residues in some skimmer eggs were high (up to 51 ppm, wet weight), with 35% of all eggs sampled containing- >1 0 ppm DDE. However, eggshell thinning of only 4-12% was demonstrated on a colony basis and log DDE residues in individual eggs were not significantly correlated with shell thickness. DDE residues in Texas eggs were 5-fold higher than in South Carolina eggs where no shell thinning was detected.

Journal of Field Ornithology↗