Ardea Herodias Research Articles

Elemental profiles in feather samples from a mercury-contaminated lake in central california

Flight feathers from six bird species at Clear Lake, CA were analyzed to determine the extent and distribution of mercury contamination from an abandoned mercury mine and associated levels of 14 other elements. Feather samples were collected from adult and juvenile osprey (Pandion haliaetus), including juvenile osprey from three additional comparison sites; adult western grebes (Aechmophorus occidentalis); adult great blue herons (Ardea herodias); adult mallards (Anas platyrhynchos); adult turkey vultures (Cathartes aura); and juvenile double-crested cormorants (Phalacrocorax auritus). Samples were analyzed by a multielemental x-ray fluorescence method. The osprey from Clear Lake showed significantly elevated mercury concentrations relative to the comparison sites. Different species at Clear Lake had different mercury concentrations based on trophic status; osprey exhibited the highest mercury concentrations and the mallards showed the lowest. Lastly, we quantified differences in elemental concentrations, including mercury, between adult and juvenile osprey from Clear Lake. Elements known to be nutrients, such as sulfur and zinc, did not vary significantly among species or sites. Reproductive success of osprey at Clear Lake was monitored from 1992 to 1996 to determine if osprey reproduction was depressed. During this five-year period, the breeding population grew from 10 to 20 nesting pairs and the average reproductive rate was 1.4 fledglings per nesting attempt. Although the osprey showed the highest mercury levels of any species sampled, their reproduction does not appear to be depressed.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) Induces Hepatic Cytochrome P450-Dependent Arachidonic Acid Epoxygenation in Diverse Avian Orders: Regioisomer Selectivity and Immunochemical Comparison of the TCDD-Induced P450s to CYP1A4 and 1A5

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) markedly induced cytochrome P450 (CYP)-dependent arachidonic acid metabolism in liver microsomes from hatchlings of four avian species belonging to four different orders: chick, pigeon, cormorant, and great blue heron, increasing formation of arachidonic acid epoxides (EETs), monohydroxyeicosatetraenoic acids (HETEs), ω−1, and ω−2 OH arachidonic acid products by fivefold or more. Microsomes from TCDD-induced hatchling chicks had the highest activity and the least restricted EET regioselectivity. ω-OH arachidonic acid, the principal constitutive metabolite in chick and pigeon liver microsomes and a major product for cormorant and great blue heron was not induced by TCDD. Constitutive EET formation in avian liver microsomes was very low except in cormorant microsomes where 8,9-EET was generated almost exclusively. Western blots of liver microsomes using polyclonal antisera to chick embryo-derived CYP1A4 and 1A5 recognized two TCDD-induced bands in each of the species. The chick bands had the same molecular weights as CYP1A4 and 1A5 (55 and 55.5 kDa, respectively) but those of the other species differed. Immunopurified antiserum monospecific for CYP1A5 recognized a band in microsomes from all of the avian species, and monospecific antiserum for CYP1A4 recognized a band in microsomes from chick, pigeon, and great blue heron. AntiCYP1A4 and 1A5 IgG immunoinhibited TCDD-induced mixed function oxidase activity completely in chick and chick embryo microsomes and only partially in the other avian microsomes. The results demonstrate that (1) TCDD causes much greater induction of CYP-dependent arachidonic acid metabolism, and of arachidonic acid epoxygenation in particular, in avian than in mammalian species; (2) TCDD induces two CYP1A-related enzymes in birds as in mammals; (3) CYP1A enzymes in the birds other than chicks are not identical to CYP1A4 and 1A5 but share some enzymatic and immunochemical characteristics with them; (4) constitutive ω-OH arachidonic acid in all of the avian species and 8,9-EET in cormorant are formed by CYP enzymes unrelated to CYP1A; and (5) two distinct characteristics of avian CYP1A enzymes are the acquisition by avian CYP1A4-related P450 of unique epitope(s) and by CYP1A5-related P450 of unusual catalytic effectiveness for arachidonic acid epoxygenation.

The great blue heron: a natural history and ecology of a seashore sentinel

The great blue heron: a natural history and ecology of a seashore sentinel

Evaluation of Bioenergetics Models for Predicting Great Blue Heron Consumption of Rainbow Trout at Hatcheries

Abstract We predicted consumption of rainbow trout Oncorhynchus mykiss by great blue herons Ardea herodias by combining a population estimate of predators with bioenergetics models of (1) existence metabolism (ME), (2) existence metabolism plus reproductive costs (MEBreeding), and (3) field metabolic rate (FM) for individual great blue herons. We then compared predicted consumption to directly estimated consumption by a free-ranging population of great blue herons foraging at a fish hatchery. Although the FM model predicted annual population consumption rates similar to observed annual consumption, model predictions differed significantly from directly estimated consumption for 6 months. Monthly consumption predicted by the existence metabolism models agreed with directly estimated consumption from October to June. During the breeding season (May–July), directly estimated consumption was higher than predicted by the ME model for nonbreeders but was lower than predicted by the MEBreeding model. This result...

Winter management of Californian rice fields for waterbirds

1. Recent legislation designed to reduce air pollution has restricted Californian rice‐farmers from burning rice stubble after harvest. Intentional flooding of fields during winter to speed straw decomposition is becoming increasingly common as growers seek alternatives to burning residual straw. The potential for flooded fields to act as a surrogate for destroyed wetland habitat may be an additional benefit in a region that hosts a large proportion of North America’s wintering waterbirds. We investigated the degree to which waterbirds use flooded fields and whether the method of flooding affects their use. Specifically, we tested whether waterbird use (a) was greater in intentionally flooded fields than in unflooded fields, (b) differed among flooded fields receiving different straw manipulations and (c) varied with water depth. 2. Intentionally flooded rice fields received significantly greater use by 24 of 31 species studied. Only great blue herons Ardea herodias and sandhill cranes Grus canadensis were significantly more common in unflooded fields. Geese densities did not differ between flooded and unflooded fields. 3. We found no differences in the densities of most species in flooded fields that received different straw manipulations to improve decomposition rates. Exceptions included several small shorebirds which occurred at highest densities in fields where straw was incorporated into the soil. 4. Species differed in their use of different water depths. For 14 species we tested whether preferred depths, suggested in the literature, received disproportionately higher use. Most of these species were more likely to be encountered within the suggested depth ranges. Depth, however, was a poor predictor of bird density. Depths of 15–20 cm resulted in frequent use by the greatest number of species. 5. We conclude that flooding rice fields increased suitable habitat for most, but not all, species studied. Different straw manipulation methods had little effect on most species. Water depth, however, was important in determining species occurrence. During the first half of the winter, water depths were greater than the median depths used by most species.

Two Capture Techniques for American White Pelicans and Great Blue Herons

-We describe two techniques for capturing American White Pelicans (Pelecanw erythmhynchos), Great Blue Herons (Ardea harodias), and other large wading birds in aquatic habitats. One technique involved using #3 padded jaw leghold traps modified by replacing both factory coil springs with weaker #1.5 coil springs, to reduce the closing force of the jaws, and replacing the factory chain with a length of aircraft cable and an elastic shockcord, to minimize injury caused by lunging. The second technique involved using a modified portable rocket net that can be set in shallow water. We captured 142 American White Pelicans and 23 Great Blue Herons using these two techniques. We describe situations best suited for the optimum use of each technique. Both methods are humane and cost, labor, and time efficient. Received 15 January 1998, accepted 26 May 1998.

Great Blue Heron (Ardea herodias) Uses Bread as Bait for Fish

Great Blue Heron (Ardea herodias) Uses Bread as Bait for Fish

The Great Blue Heron: A Natural History and Ecology of a Seashore Sentinel, by Robert W. Butler [Review

The Great Blue Heron: A Natural History and Ecology of a Seashore Sentinel, by Robert W. Butler [Review

Organochlorines, Mercury, and Selenium in Great Blue Heron Eggs from Indiana Dunes National Lakeshore, Indiana

In 1993, 20 great blue heron (Ardea herodias; GBH) eggs (one per nest) were collected from a colony at the Indiana Dunes National Lakeshore, Indiana (INDU). The eggs were artificially incubated until pipping and were then analyzed for organochlorines, mercury, and selenium. Livers of embryos were analyzed for hepatic microsomal ethoxyresorufin-O-dealkylase (EROD) activity. Brains were measured for asymmetry. Egg-laying began in early April and the mean clutch size was 4.2 eggs per clutch. Organochlorine concentrations were generally low (geometric mean p,p’-DDE = 1.6 /μg/g wet weight; polychlorinated biphenyl [PCB] = 4.9 μg/g); however, one egg had elevated concentrations of p,p -DDE (13 /μg/g) and PCBs (56 /μg/g). EROD activity in the embryos analyzed from INDU was not elevated. The frequency (11%) of brain asymmetry was low. Eggshells averaged 3.4% thinner than eggshells collected prior to the use of DDT. Mercury (geometric mean = 0.9 μg/g dry weight) concentrations in GBH eggs were within background levels. Selenium (4.0 μg/g dry weight) concentrations in eggs were above background levels, but below a concentration threshold associated with reproductive impairment.

Mercury Distribution in the Biota of a Great Lakes Estuary: Old Woman Creek, Ohio

A study of mercury contamination in a wetland ecosystem was undertaken to assess degree of contamination in various compartments of the food web, and determine the most important routes for mercury to enter fish species. Old Woman Creek is a freshwater estuary on the southern shore of Lake Erie and has been recognized as an important nursery area for fish. Although there is no point source of mercury to the wetland, there is evidence of biomagnification of mercury in the food web. Mercury concentrations in water were not detectable (< 20 ng/L) by methods used in this study. The sediments had a mean concentration of 0.04 /μg total Hg/g wet weight. Zooplankton, benthos, and macro-phytes had less than 0.05 μg total Hg/g wet weight, but mean concentrations in fish tissue ranged from 0.001 to 0.636 μg total Hg/g wet weight. There was a positive correlation between mercury concentration and both length and weight in channel catfish Ictalurus punctatus and common carp Cyprinus carpio. In general, channel catfish accumulated higher levels of mercury than common carp, suggesting that the pelagic food web may be more efficient in delivery of mercury (to channel catfish) than the benthic pathway (to common carp). The highest value for fish occurred in a bowfin Amia calva. Tissue from one great blue heron Ardea herodias had the highest concentration at 1.62 μg total Hg/g wet weight. In this system, as in others, top predators tended to accumulate the highest mercury levels and were therefore most susceptible to mercury poisoning, even at sublethal levels.

First Record of the Great Blue Heron for Brazil

First Record of the Great Blue Heron for Brazil

Assessment of cerebral hemispheric symmetry in hatchling chickens exposed in ovo to polychlorinated biphenyl congeners.

Previous investigators have reported that exposure to a mixture of environmental contaminants, including polychlorinated biphenyls, results in morphologic asymmetry of the cerebral hemispheres in hatchling great blue herons (Ardea herodias) and have suggested that this asymmetry may be a useful biomarker for contamination. This study was made to determine whether exposure to PCB congeners 3,3',4,4'-tetrachlorobiphenyl (IUPAC #77) and 3,3',4,4',5-pentachlorobiphenyl (IUPAC #126) causes similar asymmetry in hatchling domestic chickens (Gallus domesticus). Eggs were injected at day 0 of incubation with either a high dose, low dose, or combination of each congener. At hatching, the chicks were perfused with 10% formalin-saline. The brains were removed, sectioned and stained with cresyl violet. Width and height measurements of each hemisphere were taken at eight locations, caudal to rostral, 400 microm apart starting at the level of the anterior commissure (CA) and ending at the lobus paraolfactorius (LPO). The absolute differences between measurements of the left and right sides were used to run a univariate split plot analysis of variance to determine if the amount of asymmetry present was associated with specific congeners or doses. Significant differences in asymmetry were found between noninjected control groups and vehicle-injected control groups (p </= 0.05), but not between noninjected controls and treatment groups. A first degree orthogonal polynomial contrast analysis illustrated a linear trend with asymmetry increasing from the most caudal section at the CA to the most rostral section at the LPO for both non-injected control and treatment groups (p </= 0.05). These data indicate that asymmetry may be normal in avian brains resulting from both intrinsic structural asymmetry and extrinsic molding forces acting on the head during development. Both of these factors should be taken into consideration when assessing the usefulness of cerebral asymmetry as a biomarker.

Cytochrome P450 and organochlorine contaminants in black-crowned night-herons from the Chesapeake Bay region, USA

Black-crowned night-heron (Nycticorax nycticorax) offspring were collected from a relatively uncontaminated coastal reference site (next to Chincoteague National Wildlife Refuge, VA, USA) and two sites in the Chesapeake Bay watershed (Baltimore Harbor, MD and Rock Creek Park, Washington, DC, USA). Hepatic microsomal activities of benzyloxyresorufin-O-dealkylase and ethoxyresorufin-O-dealkylase were significantly elevated (up to sixfold and ninefold induction, respectively) in pipping embryos from the Baltimore Harbor colony compared to the reference site, whereas values in embryos from the Rock Creek Park colony were intermediate. Concentrations of organochlorine pesticides and metabolites in pipping embryos from both sites in the Chesapeake watershed were greater than at the reference site but below the known threshold for reproductive impairment. However, concentrations of 10 arylhydrocarbon receptor-active polychlorinated biphenyl (PCB) congeners and estimated toxic equivalents were up to 37-fold greater in embryos collected from these two sites in the Chesapeake Bay region, with values for toxic congeners 77 and 126 exceeding those observed in pipping heron embryos from the Great Lakes. Monooxygenase activity of pipping embryos was associated with concentrations of several organochlorine pesticides, total PCBs, arylhydrocarbon receptor-active PCB congeners, and toxic equivalents (r = 0.30–0.59), providing further evidence of the value of cytochrome P450 as a biomarker of organic contaminant exposure. Organochlorine contaminant levels were greater in 10-d-old nestlings from Baltimore Harbor than the reference site but had no apparent effect on monooxygenase activity or growth. These findings demonstrate induction of cytochrome P450 in pipping black-crowned night-heron embryos in the Chesapeake Bay region, probably by exposure to PCB congeners of local origin, and the accumulation of organochlorine pesticides and metabolites in nestling herons from Baltimore Harbor. Bio-monitoring with additional waterbird species (e.g., bald eagle, common tern, great blue heron) that appear to be more sensitive to PCBs than black-crowned night-herons is recommended to document health of waterbirds and remediation of the Chesapeake Bay.

Effects of embryonic and adult exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin on hepatic microsomal testosterone hydroxylase activities in great blue herons (Ardea herodias)

AbstractIn a continuing effort to evaluate biomarkers of exposure of great blue herons (Ardea herodias) to 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD) and related halogenated aromatic hydrocarbons, we examined the effect of TCDD on hepatic microsomal testosterone hydroxylase activities. Heron embryos were exposed in ovo to 2 μg TCDD/kg egg (or corn oil vehicle) and sacrificed at hatch or 7 d posthatch. Adult herons were exposed intraperitoneally to 20 μg TCDD/kg and sacrificed 2 weeks later. The sex of the birds was known for the adults only. Hepatic microsomes of herons of each age group were able to hydroxylate testosterone at the 2β, 6β, 15α, 16α, or 16β positions. In 7‐d‐old chicks, an additional unidentified compound was formed. The age of the untreated herons had a strong influence on the activities of the five hydroxylases, with changes of up to 17‐fold. The TCDD significantly (p &lt; 0.05) induced 2β‐, 6β‐, and 15α‐testosterone hydroxylase activities in the adult females, 15α‐ in the adult males, and 6β‐testosterone hydroxylase activity in the hatchlings. In the 7‐d‐old chicks, induction was no longer apparent. A significant correlation existed between hepatic microsomal ethoxyresorufin O‐deethylase (EROD) and 6β‐testosterone hydroxylase activity in hatchlings (r = 0.91; n = 12) and adult female herons (r = 1.0; n = 4). The TCDD‐induced changes in testosterone hydroxylase activities occurred at doses that resulted in tissue concentrations and levels of EROD induction that were environmentally relevant, but did not result in overt toxicities.

Effects of acute 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin exposure on plasma thyroid and sex steroid hormone concentrations and estrogen receptor levels in adult great blue herons

AbstractAdult great blue herons (Ardea herodias) were exposed intraperitoneally to a single dose of 20 μg/kg body weight of 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD) and sacrificed after 14 d. Approximately 1.9% of the total TCDD dose was measured in the liver. No differences were found in liver weight or liver to body weight ratio between control and TCDD‐treated birds. Hepatic microsomal ethoxyresorufin O‐deethylase (EROD) activity was induced sixfold above control activities in TCDD‐exposed herons (p &lt; 0.001). Plasma total T4 concentration was significantly elevated in TCDD‐exposed herons (p &lt; 0.05). The TCDD treatment had no effect on plasma total T3 levels, or on the plasma T3 to T4 ratio. No effect of this TCDD exposure was found on plasma 17β‐estradiol or testosterone concentrations, or on hepatic estrogen receptor affinities and concentrations is male or female herons.

Contaminant concentrations and biomarker response in great blue heron eggs from 10 colonies on the upper Mississippi River, USA

AbstractIn 1993, great blue heron (Ardea herodias; GBH) eggs were collected from 10 colonies on the upper Mississippi River (UMR). They were then artificially incubated until pipping and analyzed for mercury, selenium, and organochlorines. Livers of embryos were analyzed for hepatic microsomal ethoxyresorufin‐O‐dealkylase (EROD) activity and four measures of oxidative stress. Brains were measured for asymmetry and blood was measured for the coefficient of variation of DNA (DNA CV). Organochlorine concentrations were generally low (geometric mean DDE = 1.3 μg/g wet weight; polychlorinated biphenyl [PCB] = 3.0 μg/g; 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin [TCDD] = 11.5 pg/g). Eggshell thickness was negatively correlated with DDE concentrations. Mercury (geometric mean = 0.8 μg/g dry weight) and selenium (3.1 μg/g dry weight) concentrations in GBH eggs were within background levels. EROD activity was not correlated with total PCBs, TCDD, or toxic equivalents (TEQs), based on the relative contribution of individual PCB congeners, dibenzodioxins (PCDDs), and dibenzofurans (PCDFs) to total calculated TEQs. Three of the four measures of oxidative stress were correlated with mercury concentrations. Twenty of 43 (47%) embryo brains were asymmetrical and the embryos with asymmetrical brains had higher EROD concentrations in the liver and higher DNA CV in the blood than embryos with symmetrical brains.

Siblicidal attacks by Great Blue Heron, Ardea herodias, chicks in a southern Ontario heronry

Siblicidal attacks by Great Blue Heron, Ardea herodias, chicks in a southern Ontario heronry

Determinants of the Size and Location of Great Blue Heron Colonies

Determinants of the Size and Location of Great Blue Heron Colonies

Morphometric Brain Abnormalities in Double-Crested Cormorant Chicks Exposed to Polychlorinated Dibenzo- p-Dioxins, Dibenzofurans, and Biphenyls

We examined brains from double-crested cormorant hatchlings from colonies known to be contaminated with low, moderate, and high levels of PCBs, as well as PCDDs and PCDFs, in order to evaluate whether such chemical exposure during embryonic development would result in a TCDD- and TEQ-related induction of gross brain asymmetry as described previously in similarly exposed great blue herons. Our results demonstrate that cormorant embryos exposed in ovo to elevated mixtures of PCBs, PCDDs, and PCDFs in the environment are likely to hatch with asymmetric brains, when the width (medial-lateral), angle (oblique to the medio-lateral axis), height (rostro-caudal), and depth (dorso-ventral) were measured both from dorsal and ventral perspectives. The degree and frequency of this asymmetry correlates to dose based on both TCDD alone and TEQs. This indicates that the TEQ-related brain asymmetry is not a species-specific response. The gross brain asymmetries are present in hatchlings and are readily quantifiable. Thus, they could potentially be used as a biomarker of the effects of TCDD-related compounds on neuromorphological development.

Effectiveness of Alarm–Distress Calls for Frightening Herons from a Fish Rearing Facility

Abstract We evaluated the effectiveness of using alarm-distress calls of the black-crowned night heron Nycticorax nycticorax and the great blue heron Ardea herodias for frightening these piscivorous bird species from a rearing unit for rainbow trout Oncorhynchus mykiss. Heron alarm–distress calls reduced black-crowned night heron numbers 48% during the 11-d treatment period, compared with the pretreatment period, but did not affect the number of great blue herons. The number of black-crowned night herons using the rearing unit and the proportion that remained immediately after the broadcast of alarm–distress calls increased from nights 1 through 11 of the treatment period, which indicates that this predator quickly habituated to the calls. We did not find any differences between the proportions of black-crowned night herons and great blue herons that remained on the rearing unit immediately after playing calls of the respective species. Alarm–distress calls were mostly ineffective in reducing heron predat...