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T. W. Custer

Publications and source records attributed to T. W. Custer.

At least 73 records · Page 4Linked to original sources
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↗
USGS1994

Flow cytometry for monitoring contaminant exposure in black-crowned night-herons

The flow cytometry method (FCM) was employed to determine cellular DNA content of black-crowned night-heron ( Nycticorax nycticorax ) embryos and 10-day-old chicks collected at sites differing in types of chemical contamination. The coefficient of variation of DNA content (CV) in blood collected from embryos suggested cytogenetic damage at a site in Louisiana known to be contaminated with petroleum. Blood CV from chicks suggested genetic damage at a site in Texas also known to be contaminated with petroleum. Spleen CVs in chicks were significantly lower than respective means from the reference site. The CVs of chick blood and liver and spleen negatively correlated, suggesting recovery of spleen and liver cells after exposure to a clastogenic compound. Thus, the lower CVs may also have been indicative of genetic damage. Based on the findings of this study, FCM is a potential indicator of certain environmental contaminants in black-crowned night-herons.

Archives of Environmental Contamination and Toxico↗
USGS1994

Reproductive success of barn swallows nesting near a selenium-contaminated lake in east Texas, USA

Reproductive success and contaminant levels in 1986 and 1987 were compared between Barn Swallows nesting at selenium-contaminated Martin Lake, Texas, USA, and swallows nesting at a reference site. Nests were initiated about the same time or earlier at Martin Lake than at the reference site and clutch size was similar between the two locations. Nest success was significantly higher at Martin Lake than at the reference site and no embryo or chick deformities were documented. Selenium concentrations in 14 of 20 eggs from Martin Lake were above background (> 3 ppm, dry weight); two of 20 eggs contained > 5 ppm, a concentration associated with a 20% embryo mortality/deformity rate in some bird species. Selenium concentrations in the kidneys of adult swallows were higher at Martin Lake (mean = 14 ppm dry weight) than at the reference site (5·8 ppm). DDE, the only detected organochlorine compound, was in two of 10 eggs from Martin Lake; these concentrations were below those associated with chronic poisoning and reproductive problems. The maximum mercury concentration in livers of adult Barn Swallows (0·83 ppm, dry weight) was within the range for background levels (>5 ppm).

Texas↗
USGS1994

Prevalence of eustrongylidosis in wading birds from colonies in California, Texas, and Rhode Island, USA

Snowy Egret (Egretta thula) and Black-crowned Night-Heron (Nycticorax nycticorax) nestlings from colonies in Texas, Rhode Island, and California and Great Egret (Casmerodius albus) nestlings from Texas were examined for eustrongylidosis, or infection by the parasitic nematode Eustrongylides spp. In 31% (24/77) of all broods examined, at least one nestling was infected. Snowy Egret broods from Texas were more frequently (100%) infected than those from California (20%) or Rhode Island (10%), and the prevalence of eustrongylidosis in 5- and 10-day-old Snowy Egret nestlings was higher in the Texas colony than the other two. Within the Texas colony, the frequency of eustrongylidosis was greater for Snowy Egret (100%) and Great Egret (80%) broods than for Black-crowned Night-Heron broods (12.5%). Also in Texas, eustrongylidosis was more frequent in 5-day-old Snowy Egret nestlings than 5-day-old Black-crowned Night-Heron or Great Egret nestlings, and in 10-day-old Snowy Egret nestlings than in 10-day-old Black-crowned Night-Heron nestlings. Eustrongylides spp. caused perforations of the gastrointestinal tract and peritonitis, particularly in Snowy Egrets.

California, Rhode Island, Texas↗
USGS1993

Biomonitoring environmental contamination with pipping black-crowned night heron embryos: Induction of cytochrome P450

Cytochrome P450-associated monooxygenase activities and cytochrome P450 proteins were measured in pipping black-crowned night heron ( Nycticorax nycticorax ) embryos collected from a reference site (next to the Chincoteague National Wildlife Refuge, VA) and three polluted sites (Cat Island, Green Bay, Lake Michigan, WI; Bair Island, San Francisco Bay, CA; West Marin Island, San Francisco Bay, CA). In a laboratory study, artificially incubated night heron embryos from the reference site were treated with 3-methylcholanthrene (200 μg administered into the air cell 2 d before pipping) or phenobarbital (2 mg daily for 2 d before pipping). Compared to controls (untreated + vehicle-treated embryos), 3-methylcholanthrene induced a greater than fivefold increase in activities of several monooxygenases (arylhydrocarbon hydroxylase, AHH; benzyloxyresorufin- O -dealkylase, BROD; ethoxyresorufin- O -dealkylase, EROD; pentoxyresorufin- O -dealkylase, PROD) and a greater than 100-fold increase in the concentration of immunodetected cytochrome P450 1A (CYP1A). Phenobarbital treatment resulted in only a slight increase in BROD activity but induced proteins recognized by antibodies to cytochrome P450 2B (CYP2B) by 2,000-fold. In a field study, activities of AHH, BROD, EROD, and ethoxycoumarin- O -dealkylase (ECOD) were up to 85-fold higher in pipping black-crowned night herons collected from Cat Island compared to other sites. Hepatic CYP1A and CYP2B cross-reactive proteins were detected in significantly more individuals from Cat Island than from the reference site. Greatest burdens of total PCBs and p,p ′-DDE were detected in embryos from Cat Island. Cytochrome P450-associated monooxygenase activities and cytochrome P450 proteins (AHH, BROD, EROD, ECOD, CYP1A, CYP2B) were significantly associated with total PCB burdens ( r = 0.50-0.72). These data indicate that cytochrome P450 may be a useful biomarker of exposure to some PCB mixtures in black-crowned night heron embryos.

Environmental Toxicology and Chemistry↗
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↗
USGS1992

Feeding flights of breeding double-crested cormorants at two Wisconsin colonies

Unmarked Double-crested Cormorants (Phalacrocorax auritus ) were followed by airplane from Cat Island and Spider Island, two nesting colonies in Wisconsin, to their first landing site. Cormorants flew an average of 2.0 km from Cat Island (maximum 40 km) and 2.4 km from Spider Island (maximum 12 km). The mean direction of landing sites differed seasonally for flights from Spider Island, but not from Cat Island, Cormorants generally landed in Green Bay or Lake Michigan and rarely landed in inland lakes or ponds. The most frequent water depth at landing sites for each colony was < 9.1 m. Water depths greater than or equal to 9.1 m were used less frequently than available within the maximum observed flight distance for each colony. The average flight speed for cormorants was 61 km/h.

Wisconsin↗
USGS1992

Determination of hatching date for eggs of black-crowned night-herons, snowy egrets and great egrets

Floatation of eggs in water and specific gravity of eggs of Black-crowned Night-Herons (Nycticorax nycticorax ), Snowy Egrets (Egretta thula ) and Great Egrets (Casmerodius albus ) were evaluated as methods to determine date of hatching. Although specific gravity was a better predictor of hatching date than egg flotation, both techniques were imprecise. The regression between specific gravity and the number of days before hatching differed among clutches, but not among eggs within clutches. Specific gravity of eggs predicted hatching date only to within 3.8 d for Snowy Egrets, and 4.7 d for Black-crowned Night-Herons and Great Egrets. The mean incubation period was 27.3 d for Great Egrets, 23.7 d for Snowy Egrets and 22.8 d for Black-crowned Night- Herons. For all three species, the A egg (first egg laid) had a longer incubation period than the B or C egg.

Journal of Field Ornithology↗
USGS1992

Feeding flights of breeding double-crested cormorants at two Wisconsin colonies

Unmarked Double-crested Cormorants (Phalacrocorax auritus) (n = 523) were followed by airplane from Cat Island and Spider Island, two nesting colonies in Wisconsin, to their first landing site. Cormorants flew an average of 2.0 km from Cat Island (maximum 40 km) and 2.4 km from Spider Island (maximum12 km). The mean direction of landing sites differed seasonally for fights from Spider Island, but not from Cat Island. Cormorants generally landed in Green Bay or Lake Michigan (>99%) and rarely landed in inland lakes or ponds. The most frequent (> 80%) water depth at landing sites for each colony was < 9,1 m. Water depths >9.l m were used less frequently than available within the maximum observed flight distance for each colony. The average flight speed for cormorants was 61 km/h.

Wisconsin↗
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↗
USGS1992

Determination of hatching date for eggs of black-crowned night-herons, snowy egrets and great egrets

Flotation of eggs in water and specific gravity of eggs of Black-crowned Night-Herons (Nycticorax nycticorax), Snowy Egrets (Egretta thula) and Great Egrets (Casmerodius albus) were evaluated as methods to determine date of hatching. Length of incubation and duration of hatching period were also documented for each species. Although species gravity was a better predictor of hatching date than egg flotation, both techniques were imprecise. The regression between specific gravity and the number of days before hatching differed among clutches, but not among eggs within clutches. Specific gravity of eggs predicted hatching data only to within 3.8 d for Snowy Egrets, adn 4.7 d for Black-crowned Night-Herons and Great Egrets. The mean incubation period was 27.3 d for Great Egrets, 23.7 d for Snowy Egrets and 22.8 d for Black-crowned Night-Herons. For all three species, the A egg (first egg laid) had a longer incubation period than the B or C egg. For all three species, the number of days between hatching of A and B eggs was significantly less (median - 1 d) than between hatching of B and C eggs (median = 2 d).

Journal of Field Ornithology↗
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↗
USGS1991

Growth rates of great egret, snowy egret and black-crowned night-heron chicks

Growth rates of Great Erget (Casmerodius albus), Snowy Erget (Egretta thula), and Black-crowned Night-Heron (Nycticorax nycticorax) chicks to 18 days-of-age were estimated from repeated measurements of chicks in broods of three young. Weight gain (g/day) or increase in length (mm/day) of forearm, tarsus, or culmen did not between Black-crowned Night-Heron chicks at a colony in Rhode Island and a colony in Texas (USA). In Black-crowned night-Herons and Great Egrets, the last chick (C-chick) to hatch had lower growth rates than the first (A-) or second (B-) hatched chick. Black-crowned Night-Heron and Great Egret A-chicks gained weight faster than Snowy Egret A-chicks; however growth rates of the forearm, tarsus, or culmen each were not different among the three species. Equations based on the growth rate of culmen, forearm, or tarsus for repeatedly measured A-chicks estimated age of Great Egret, Snowy Egret, and Black-crowned Night-Heron chicks collected elsewhere to within two days of known age.

Colonial Waterbirds↗
USGS1991

Green coloration of recently laid black-crowned night-heron eggs

Color of Black-crowned Night-Heron (Nycticorax nycticorax) eggs of known laying order was quantified in a Wisconsin (USA) colony. Eggs were of greener intensity on the day of laying and one day thereafter than earlier laid eggs within a clutch. Egg color can be used to identify clutches within one day after clutch completion and to assign laying order within clutches during this period.

Colonial Waterbirds↗
USGS1991

Herons and egrets as proposed indicators of estuarine contamination in the United States

The National Contaminant Biomonitoring Program of the U.S. Fish and Wildlife Service Includes the sampling of freshwater fish, starlings, and duck wings. In order to include an estuarine component, herons and egrets are being evaluated. Organochlorine concentrations were measured In eggs and chicks of Snowy Egrets Egretta thula, Great Egrets Casmerodius albus, and Black-crowned Night-Herons Nycticorax nycticorax collected In Rhode Island, Texas, and California. Chicks of all species at all locations accumulated DDE and polychlorinated biphenyls (PCBs), and accumulation rates may serve as the basis for an indicator program of estuarine contamination. Biochemical re-sponses of embryos and chicks were also evaluated. Microsomal arylhydrocarbon hydroxylase and benzyloxyresorufin-O-dealkylase activities in livers of 10-day-old night-heron chicks were elevated at a contaminated site in San Francisco Bay, CA, when compared to a 'reference' site in Vlrginia. Quantification of liver enzyme activities may serve as a rapid cost-effective biomarker of pollutant exposure.

Book chapter↗
USGS1991

Organochlorines accumulate in heron and egret chicks sampled in the Houston Ship Channel

The National Contaminant Monitoring Program (NCBP) is an effort of the U.S. Fish and Wildlife Service to measure concentrations of DDT and other persistent chemicals in the environment and to quantify changes in these levels. The NCBP has established a network of sampling stations in segments of the environment for which Federal agencies have authority. The wildlife component of this program, administered by the Patuxent Wildlife Research Center, includes the periodic sampling of European starlings (Sturnus vulgaris), mallards (Anas platyrhynchos), and American black ducks (Anas rubripes). In order to include an estuarine component into the NCBP, herons and egrets are being evaluated. Eggs and chicks (five, ten, and 15 days of age) of snowy egrets (Egretta thula), and black-crowned night-herons (Nycticorax nycticorax) were collected in Naragansett Bay, RI; the Houston Ship Channel (HSC), TX; and San Francisco Bay, CA. Great egret (Casmerodius albus) eggs and chicks also were collected at the Texas colony. Eggs and chicks were analyzed for organochlorines; trace element and petroleum hydrocarbon analyses are pending. DDE and polychlorinated biphenyls (PCBs) were detected in all eggs and chicks, and they accumulated as the chicks grew. At each location, black-crowned nightheron chicks accumulated both DDE and PCBs more rapidly than snowy egrets or great egrets. PCBs accumulated more rapidly in night-heron chicks in Rhode Island than California; however, PCB accumulation for snowy egret chicks did not differ among locations. Contaminant accumulation rates in heron and egret chicks could be used as a new wetland component of the NCBP.

Book chapter↗
USGS1990

Within- and among-clutch variation of organochlorine residues in eggs of black-crowned night-herons

Within-clutch variability of DDE and PCB residues in eggs from 62 clutches of black-crowned night-herons ( Nycticorax nycticorax ) was small (12% and 17%) compared to among-clutch variability (88% and 83%). Significant correlations between concentrations of DDE (median r =0.8885) and of PCBs (median r =0.8244) occurred when 501 correlations were run on two randomly selected eggs from within the same clutch; no significant correlation occurred for either concentrations of DDE (median r =0.0353) or PCBs (median r =−0.0843) when eggs were not restricted to the same clutch but were restricted to the same colony. The probability of finding infrequently detected organochlorine contaminants (e.g., DDT, cis -chlordane) in eggs from the same clutch varied from 43–96% and increased as the chemical became more prevalent and the number of eggs per clutch became smaller. These results further support one of the basic assumptions of the sample egg technique, that the chemical residues in one egg in a clutch accurately reflect residues in the remaining eggs of the clutch.

Environmental Monitoring and Assessment↗