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C. A. Mitchell

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

28 records · Page 2Linked to original sources
USGS1983

Parathion alters incubation behavior of laughing gulls

One member of each pair of incubating laughing gulls at 9 nests was trapped, orally dosed with either 6 mg/kg parathion in corn oil or corn oil alone, and marked about the neck with red dye. Each nest was marked with a numbered stake and the treatment was recorded. A pilot study with captive laughing gulls had determined the proper dosage of parathion that would significantly inhibit their brain AChE activity (about 50% of normal) without overt signs of poisoning. After dosing, birds were released and the nests were observed for 21/2 days from a blind on the nesting island. The activities of the birds at each marked nest were recorded at 10-minute intervals. Results indicated that on the day of treatment there was no difference (P>0.05, Chi-square test) in the proportion of time spent on the nest between treated and control birds. However, birds dosed with 6 mg/kg parathion spent significantly less time incubating on days 2 and 3 than did birds receiving only corn oil. By noon on the third day, sharing of nest duties between pair members in the treated group had approached normal, indicating recovery from parathion intoxication. These findings suggest that sublethal exposure of nesting birds to an organophosphate (OP) insecticide, such as parathion, may result in decreased nest attentiveness, thereby making the clutch more susceptible to predation or egg failure. Behavioral changes caused by sublethal OP exposure could be especially detrimental in avian species where only one pair member incubates or where both members are exposed in species sharing nest duties.

Texas↗
USGS1983

Azodrin poisoning of waterfowl in rice fields in Louisiana

During the period 2-4 April 1981 about 100 birds, mostly ducks and geese, were found dead and dying in a rice field near Sweet Lake, Calcasieu Parish, Louisiana. Fresh specimens were collected to determine the cause of mortality. Birds were placed individually in polyethylene freezer bags, tagged, and frozen soon after collection. Four snow geese (Chen caerulescens), two blue-winged teal (Anas discors), one green-winged teal (Anas crecca), and one mottled duck (Anas fulvigula) were shipped to the National Wildlife Health Laboratory (NWHL), Madison, Wisconsin, for necropsy and pathological examination. Ten snow geese, 10 blue-winged teal, three green-winged teal, three great-tailed grackles (Quiscalus mexicanus), and eight red-winged blackbirds (Agelaius phoeniceus) were transported to the Gulf Coast Field Station, Victoria, Texas, for brain acetylcholinesterase (AChE) activity determinations and preparation for chemical residue analysis. Additionally, apparently healthy specimens of the affected species were collected near Lake Charles, Louisiana, and Victoria, Texas, to serve as controls in the analyses.

Louisiana;Texas↗
USGS1983

Elevated DDE and toxaphene residues in fishes and birds reflect local contamination in the lower Rio Grande Valley, Texas

A potential organochlorine pesticide problem was identified near Mission, Texas, by the National Pesticide Monitoring Program. Fish samples from this site have consistently contained elevated levels of DDE since 1968. Surveys were made in 1976, 1978, and 1979 to determine the extent of organochlorine pesticide contamination in fishes and birds of the area. Freshwater fishes of the Arroyo Colorado, a major waterway traversing the lower Rio Grande Valley, were highly contaminated with DDE and toxaphene residues compared to samples from other areas in the Valley; both DDE and toxaphene ranged up to 31.5 ppm wet weight in whole-fish composite samples. In addition, median DDE residues in fish-eating bird carcasses from this area ranged up to 34 ppm wet weight, and 81 ppm in individual specimens. The levels of contaminants detected in fishes and birds were within, or above, the range producing adverse effects in certain species. The major sources of contamination to the Arroyo Colorado system likely stem from past and present use of persistent pesticides on surrounding croplands, and possibly from an abandoned pesticide plant at Mission, Texas.

Southwestern Naturalist↗
USGS1983

Nesting biology of laughing gulls in relation to agricultural chemicals in south Texas USA 1978-1981

Various aspects of the breeding biology of Laughing Gulls ( Larus atricilla ) have been studied extensively in Florida (Dinsmore and Schreiber 1974, Schreiber et al. 1979, Schreiber and Schreiber 1980), New Jersey (Bongiorno 1970, Burger and Beer 1976, Burger 1976, Montevecchi 1978), and Massachusetts (Noble and Wurm 1943), but little is known of their yearly fledging success in Texas or elsewhere. The Laughing Gull is a common colonial nester along most of the Texas coast, second only to the Cattle Egret ( Bubulcus ibis ) in breeding abundance; however, the Laughing Gull may be threatened in Texas because of suspected declines at certain traditional nesting locales (Blacklock et al. 1979). Since Laughing Gulls often nest in proximity to agricultural and industrial areas, we were concerned that environmental pollutants might be adversely affecting productivity. In 1978-1981 we conducted studies along the south Texas coast to learn more about the nesting ecology of Laughing Gulls and to evaluate the effects of environmental contaminants on reproduction.

Texas↗
USGS1982

Seasonal brain acetylcholinesterase activity in three species of shorebirds overwintering in Texas

There was no seasonal variation in average brain AChE activity for the 3 species of wild birds collected between October and February. Further work needs to be done, however, covering an even broader time frame which includes the reproductive cycle. It appears that some birds feeding at the mouth of an agricultural drain, at some distance from the nearest pesticide applications, were affected by AChE inhibitors.

Bulletin of Environmental Contamination and Toxico↗
USGS1982

Organophosphate insecticide poisoning of Canada geese in the Texas panhandle

Sixteen hundred waterfowl, mostly Canada Geese, died near Etter, Texas, in late January 1981 from anticholinesterase poisoning. Winter wheat in the area of the die-off had been treated with organophosphate insecticides to control greenbugs. Cholinesterase (ChE) levels in brains of a sample of geese found dead were 75% below normal, enough to account for death (Ludke et al. 1975). The gastrointestinal (G I) tracts of geese found dead were packed with winter wheat; gas chromatography techniques identified parathion and methyl parathion in the GI tract contents. Residues of both chemicals were confirmed by mass spectrometry. We recommend that less toxic materials, such as malathion, be used on grain crops when waterfowl are in the vicinity of treatment.

Texas↗
USGS1981

Body lipids and pesticide burdens of migrant blue-winged teal

Blue-winged Teal were collected before and after their migration to wintering grounds in Latin America. Pesticide burdens, body weights, and lipid levels of carcasses were determined. Only DDE and dieldrin were detected in a small proportion of the samples and then at concentrations far below known-effect levels. Residue loads, because of their infrequency, were not significantly correlated with overall body weight and percent lipid. Body weights among most age and sex classes did not differ in either fall or spring, nor did percent lipid in any instance. However, body weights and lipid levels were significantly correlated; as body weight increased so did percent lipid. Thus, the extreme variability in body weight appears to be a function of the amount of fat present and not overall body size, age, or sex.

Journal of Field Ornithology↗
USGS1979

Parathion causes secondary poisoning in a laughing gull breeding colony

Use of organophosphate insecticides as replacements for the more persistent organochlorine compounds has increased dramatically in recent years. Organophosphates are desirable for field application because they break down rapidly in the environment and do not persist in animal tissues (Stickel 1974). Nevertheless, certain organophosphates are extremely toxic to wildlife for short periods after application and have caused widespread mortality among exposed animals (Mills 1973, Stickel 1974, 1975, Mendelssohn 1977, and Zinkl et al. 1978).

Texas↗