Nycticorax Nycticorax Research Articles

Comparison of nestling nutrition and growth of Black-crowned Night Heron, Nycticorax nycticorax, and Little Egret, Egretta garzetta

Comparison of nestling nutrition and growth of Black-crowned Night Heron, Nycticorax nycticorax, and Little Egret, Egretta garzetta

Responses of Nestling Black-crowned Night Herons (Nycticorax nycticorax ) to Aquatic and Terrestrial Recreational Activities: a Manipulative Study

We assessed the effects of the presence and the frequency of canoe and pedestrian disturbance during two breeding seasons on multiple behavioral responses (scanning, freezing, grooming, sleeping, moving, wing-raising, and standing-up) of Black-crowned Night Heron (Nycticorax nycticorax) nestlings in a breeding colony in southeast Chicago. Short-term responses (min) of Black-crowned Night Heron nestlings showed that they were sensitive to the presence of aquatic and pedestrian disturbance by increasing vigilant (scanning) and anti-predator (freezing) behaviors and decreasing maintenance (grooming, sleeping) behaviors. Nestlings were also sensitive to recreationist behavior, with less time allocated to sleeping and more time to freezing and scanning in the presence of inquisitive pedestrians than pedestrians who passed by the colony without stopping. However, medium-term responses (days) were insensitive to the frequency of disturbance, but spatial proximity to the source of disturbance influenced time scanning, sleeping, and freezing). Our results have wide implications for the protection of the Black-crowned Night Heron in States in which it is considered a species of conservation concern. We recommend that boating activities should be precluded during the initial part of the breeding season and buffer zones of 50 m should be established around the colony to minimize human disturbance. However, under these conditions, restrictions on the number of visitors during the breeding period may not be necessary.

The Status of Colonial Nesting Wading Bird Populations Within the Chesapeake Bay and Atlantic Barrier Island-Lagoon System

Colonially nesting wading birds (herons, egrets, and ibis) are a highly visible, biologically significant component of the mid-Atlantic coastal avifauna. Populations of these species were decimated by extensive market hunting in the late nineteenth century, recovered, and additional species colonized the region. Herein, we summarize changes in species, numbers of breeding pairs, and colony sites for ten species of wading birds surveyed four times over a 26-year period (1977 to 2003) within the Chesapeake Bay and Atlantic coastal barrier island region. Over the period of surveys, wading bird breeding colonies increased 246% (to 537) and numbers of breeding pairs increased 67% (to 26,589). Expansion among Great Blue Herons (Ardea herodias), Great Egrets (Ardea alba), Yellow-Crowned Night-Herons (Nyctanassa violacea) and Glossy Ibis (Plegadis falcinellus), primarily accounted for the dramatic increase, while declines were recorded for Snowy Egrets (Egretta thula), Cattle Egrets (Bubulcus ibis) and Black-crowned Night-Herons (Nycticorax nycticorax). Rapid loss of breeding wading birds along the Atlantic coastal lagoon system during the last decade is of particular conservation concern.

Contaminant Exposure and Biomarker Response in Embryos of Black-crowned Night-herons ( Nycticorax nycticorax) Nesting near Lake Calumet, Illinois

We examined a suite of environmental contaminants and exposure endpoints in blackcrowned night-heron ( Nycticorax nycticorax, BCNH) embryos collected in 2002 from colonies in Illinois, Minnesota, and Virginia. Embryos from the Lake Calumet, IL, colony had greater exposure to polychlorinated biphenyls (PCBs), 4,4’-dichlorodiphenyldichloroethylene (DDE), dieldrin, transnonachlor, oxychlordane, cobalt, copper, and selenium than did those from northwest MN and coastal VA. Embryos from IL and VA contained greater concentrations of mercury and zinc than those from MN, whereas the latter had greater accumulation of lead. Greater exposure of IL embryos to PCBs was reflected in greater ethoxyresorufin-O-deethylase and benzyloxyresorufin-O-dealkylase induction. However, measures of oxidative stress and genotoxicity were similar to those in embryos from the other colonies examined, and no overt toxic effects of contaminant exposure such as embryo mortality or malformations were observed. Although efforts to clean up the south Chicago environment are ongoing, Lake Calumet BCNH, and undoubtedly other piscivorous wildlife foraging in the region, continue to be exposed to a variety of environmental contaminants. Life-history characteristics of this species make it ideal as an environmental sentinel for the success of the cleanup of the south Chicago environment.

Breeding Site Preferences and the Effects of Breeding Black-crowned Night Herons (Nycticorax nycticorax) on Soil Characteristics at Bamsum Island in Seoul

Nest density was determined and tree and soil characteristics around Nycticorax nycticorax breeding sites and non-breeding sites on Bamsum Island in Seoul were analyzed from May 2005 to October 2006 to identify breeding site preferences of N. nycticorax and the effects of N. nycticorax nesting density on nesting tree structure and soil characteristics. N. nycticorax preferred trees of low height (3.5~6 m) and small diameter at breast height in high density Salix communities. Excrement of heron juveniles was dropped on the soil under the nests. The soil nutrient content under nests (P: 126.0 mg/kg, N: 202.8 mg/kg, EC: 549 μS/cm, pH 4.7) was much higher than that of control soils from Bamsum Island not enriched by heron excrement (P: 41.5 mg/kg, N: 42.0 mg/kg, EC: 342 μS/cm, pH 5.1). Formation of Salix communities on the shores of Bamsum Island is ongoing, and their structure has been directly influenced by annual flooding. After flooding, the nutrient content differences between heron-affected soils and control soils were not significant. This might be the reason that Salix communities on Bamsum were not affected by nesting herons as in other terrestrial communities where herons nest. This result indicates that flooding plays an important role in sustaining Salix communities on Bamsum Island where herons nest. The results of this study may increase understanding of N. nycticorax breeding behavior which may be useful for conservation planning.

Mercury and drought along the lower Carson River, Nevada: II. Snowy egret and black-crowned night-heron reproduction on Lahontan Reservoir, 1997–2006

Mercury concentrations in the floodplain of the Carson River Basin in northwestern Nevada are some of the highest ever reported in a natural system. Thus, a portion of the basin including Lahontan Reservoir was placed on the U.S. Environmental Protection Agency's Natural Priorities List for research and cleanup. Preliminary studies indicated that reproduction in piscivorous birds may be at risk. Therefore, a 10-year study (1997--2006) was conducted to evaluate reproduction of snowy egrets (Egretta thula) and black-crowned night-herons (Nycticorax nycticorax) nesting on Gull Island in Lahontan Reservoir. Special attention was given to the annual flow of the Carson River, the resultant fluctuation of this irrigation reservoir, and the annual exposure of snowy egrets and night-herons to methylmercury (MeHg). The dynamic character of the river due to flooding and drought (drought effect) influenced snowy egret and night-heron reproduction more so than did MeHg contamination of eggs. During an extended drought (2000--2004) in the middle of the study, snowy egret nests containing eggs with concentrations of MeHg (measured as total mercury [THg] approximately 100% MeHg) > or =0.80 microg THg/g, ww, all failed, but in 1997 and 2006 (wet years with general flooding), substantial numbers of young were produced (but fewer than at nests where eggs contained <0.80 microg/g). Thus, a variable reproductive threshold of tolerance to MeHg may be associated with habitat quality (food type and abundance). Clearly, drought was the most important factor affecting snowy egret annual productivity. In contrast to snowy egrets, night-herons generally had fewer nests meeting the 0.80 microg THg/g criterion, and those above the criterion were less sensitive to mercury than were snowy egrets. Furthermore, night-herons appeared more tolerant of drought conditions than snowy egrets because they nested earlier, selected more protected nesting sites, and had a more generalist diet that provided additional food options including terrestrial organisms, which also reduced exposure to MeHg. A putative biological effect threshold of 2.0 microg THg/g in whole blood for young of both species was evaluated, which was frequently exceeded, but with no evidence, while still in the colony, of an association with direct mortality. An evaluation of physiological associations with blood residues and post-fledging survival will be presented in future reports in this series.

Heavy Metal Distribution in Chicks of Two Heron Species from Korea

This study presents concentrations of iron, manganese, zinc, copper, lead, and cadmium in tissues of black-crowned night heron (Nycticorax nycticorax) (n = 8) and grey heron (Ardea cinerea) (n = 9) chicks from Pyeongtaek heronry, Gyeonggi-do, Korea, 2001. Iron (respectively, 45.8 +/- 24.0 microg/wet g, 155 +/- 123 microg/wet g), zinc (38.3 +/- 5.34 microg/wet g, 50.9 +/- 14.0 microg/wet g), and copper (9.93 +/- 2.26 microg/wet g, 30.2 +/- 12.9 microg/wet g) concentrations in feathers, manganese concentrations in livers (3.26 +/- 0.68 microg/ wet g, 1.50 +/- 0.58 microg/wet g), kidneys (1.43 +/- 0.27 microg/wet g, 0.84 +/- 0.34 microg/wet g), and bones (1.34 +/- 0.50 microg/wet g, 3.17 +/- 1.31 microg/wet g) were different between black-crowned night heron and grey heron chicks. Lead concentrations in bones (0.11 +/- 0.04 microg/wet g, 0.61 +/- 0.42 microg/wet g) and cadmium concentrations in liver (13.5 +/- 2.30 microg/wet kg, 10.3 +/- 1.59 microg/wet kg), kidney (6.61 +/- 2.54 microg/wet kg, 2.31 +/- 1.29 microg/wet kg), and muscle (5.25 +/- 5.91 microg/wet kg, 1.37 +/- 0.90 microg/wet kg) differed between chicks of the two heron species. The differences of heavy metal concentrations in tissues in herons and egrets were reported to other similar studies. Heavy metal concentrations for both heron species were at background levels. In both species, lead concentrations were higher in livers than in bones and cadmium concentrations were higher in livers than in kidneys. We suggest that it is not chronic exposure but acute exposure to lead and cadmium contamination around breeding site that leads to these observations. Therefore, lead and cadmium concentrations in tissues can be used as a bioindicator of acute local contamination.

Seabird and Colonial Wading Bird Nesting in the Gulf of Panama

The Gulf of Panama is a highly productive marine ecosystem at the southern edge of North America. Although the Gulf’s aquatic bird populations have been remarked upon by ornithologists for over 50 years, nesting populations have been neither systematically studied nor completely characterized. In 2005 and 2006, the entire Gulf of Panama was inventoried to document the nesting status of seabirds and other colonial waterbirds. Over 50,000 birds of 20 species nesting at 57 sites were documented. Seabirds nested during the dry season, the period of oceanographic upwelling. Coastal colonial waterbirds nested at the end of the dry season and in the early wet season, when inland feeding habitats were optimal. Brown Pelicans (Pelecanus occidentalis) were the most numerous seabird with over 4,800 nests and 10,000 individuals counted. Over 3,600 Neotropic Cormorant (Phalacrocorax brasilianus) nests and over 2,200 Magnificent Frigatebird (Fregata magnificens) nests were documented. Cattle Egrets (Bubulcus ibis) were the most abundant colonial wading birds, followed by Great Egrets (Ardea alba). Great Egrets were the first wading birds to nest, Cattle Egrets the last. Seven sites contained over 1,000 nests. Colony locations and numbers differed markedly from the historic literature. Some historic information is erroneous, but other differences reflect changes in distribution. More nesting Brown Pelicans and Sooty Terns (Sterna fuscata) and fewer Neotropic Cormorants were found than expected from the literature. New sites documented included some of global or regional conservation importance. This paper presents the first breeding records for Panama of Little Blue Heron (Egretta caerulea), Glossy Ibis (Plegadis falcinellus), and Bridled Tern (Sterna anaethetus), and third record for Cocoi Heron (Ardea cocoi). There is no evidence for long-term declines of seabirds or colonial wading birds in the Gulf of Panama. Populations reaching conservation thresholds globally or biogeographically include Brown Pelican, Bare-throated Tiger-Heron (Tigrisoma mexicanum), White Ibis (Eudocimus albus), Glossy Ibis, and Bridled Tern. The Black-crowned Night-Heron (Nycticorax nycticorax) exceeded conservation thresholds for Central America. Six new sites of global importance for bird conservation were identified and the continued importance of another site confirmed. The continued health of the waterbird populations of Panama will depend on environmental education and protection of important colony sites from disturbance and development.

Foraging Habitat Preferences of Herons and Egrets

We investigated the foraging habitat preferences of herons and egrets in an agricultural area in Asan city, Chungcheongnam-do, Korea. In the study area, rice fields were the most abundant habitat type (86.8%) and total suitable feeding habitat was greater in the northern area (59.0%) than the southern area (22.5%) of the colony. Most feeding herons and egrets were located in the northern area of the colony. The number of feeding individuals in a given area was related to the available feeding area (Pearson correlation, r=0.773, p< 0.001 for field habitats; r=0.901, p< 0.001 for freshwater habitats). Feeding habitat preferences differed among species. Grey herons ( Ardea cinerea ), great egrets ( Egretta alba ), and black-crowned night herons ( Nycticorax nycticorax ) used reservoirs and ditches. However, intermediate egrets ( E. intermedia ) and cattle egrets ( Bubulcus ibis ) were dependent on rice fields. The little egret ( E. garzetta ) was a habitat generalist using all types of habitats. The two largest species, grey herons and great egrets, fed at deeper site than little egrets and foraged in deeper sites in reservoirs than in ditches ( χ 2 -test, χ 2 3=26.6 and p< 0.001 for grey herons, χ 2 3 =17.5 and p< 0.001 for great egrets). All species displayed seasonal changes in feeding habitat use and these changes were related with changes in availability of feeding habitats.

The Use of Feathers to Monitor Heavy Metal Contamination in Herons, Korea

This study measured concentrations of iron, manganese, zinc, copper, lead, and cadmium in environmental substrates (water and sediment) as well as in the diet and feathers of Black-crowned Night Heron Nycticorax nycticorax and Grey Heron Ardea cinerea chicks from Pyeongtaek heronry, Gyeonggi-do, Korea. Zinc and cadmium concentrations in sediment were relatively high, but lead was low. In the diet, only copper concentrations were higher in Black-crowned Night Herons than in Grey Herons. Cadmium concentrations in the diet of two heron species from a Pyeongtaek heron colony were also higher than reported in other studies. In feathers, iron, copper, and lead concentrations were significantly different between heron species. Iron and copper concentrations were higher in Black-crowned Night Heron chicks than in Grey Heron chicks, but lead concentrations were not. Therefore, with the exception of lead, heavy metal concentrations in feathers were not related to concentrations in the diet. Zinc, iron, and lead concentrations in heron feathers were within the ranges reported by other heron studies, but manganese, copper, and cadmium were much higher. Lead and cadmium concentrations in feathers of Black-crowned Night Heron and Grey Heron chicks were elevated to lead and cadmium concentrations in the diet. Therefore, we suggest that lead and cadmium concentrations in heron feathers reflect contamination of breeding sites and are useful bioindicators of local contamination.

Health assessment of Black-crowned Night-herons ( Nycticorax nycticorax) of the New York Harbor estuary

Blood samples from 145 Black-crowned Night-heron ( Nycticorax nycticorax, BCNH) chicks (mean age 3 weeks) were taken from four island colonies (Goose (2004), Canarsie Pol (2005), Hoffman (2004 and 2005) and North Brother (2004 and 2005)) in New York Harbor in 2004 and 2005 to establish baseline health reference ranges for this species and to compare health indices of birds reared on different islands. Packed cell volume (PCV) and total solids (TS) did not differ among islands in either year. Herons raised on Hoffman Island in 2004 had lower white blood cell count (WBC), and higher activities of creatine phosphokinase (CPK), lactate dehydrogenase (LDH), aspartate amino transferase (AST), higher concentrations of potassium (K) and phosphorous (PHOS) and lower liver derived proteins (TP, prealbumin, albumin, alpha 1 globulins, alpha 2 globulins, beta globulins and gamma globulins) compared to herons from Goose and North Brother Islands. These changes suggest compromised health in chicks reared on Hoffman Island in 2004. On Hoffman in 2005, these biochemical analytes did not differ from concentrations and enzyme activities measured from birds on other islands. Although no single etiology can explain these extensive changes, it is likely that exposure to contaminants at foraging sites used by birds nesting on Hoffman and/or changes in prey availability and abundance causing birds to forage in different locations between years, led to differences measured in blood-based health indices. Avian health assessments coupled with foraging ecology serve as an excellent method for evaluating ecosystem health of the New York Harbor estuary system.

Mercury and Drought Along the Lower Carson River, Nevada: I. Snowy Egret and Black-Crowned Night-Heron Annual Exposure to Mercury, 1997–2006

The dynamic nature of the annual volume of water discharged down the Carson River over a 10-year period, which included a century flood and drought, was examined in order to gain a better understanding of mercury movement, biological availability, and exposure to waterbirds nesting at Lahontan Reservoir. Total annual water discharge directly influenced total mercury (THg) in unfiltered water above the reservoir and downstream of a mining area, whereas methyl mercury (MeHg) at the same site was negatively related to annual discharge. Annual water storage at Lahontan Reservoir in the spring and early summer, as expected, was directly related to annual Carson River discharge. In contrast to the findings from above the reservoir, annual MeHg concentrations in water sampled below the reservoir were positively correlated with the total discharge and the amount of water stored in the reservoir on 1 July; that is, the reservoir is an important location for mercury methylation, which agrees with earlier findings. However, unfiltered water MeHg concentrations were about 10-fold higher above than below the reservoir, which indicated that much MeHg that entered as well as that produced in the reservoir settled out in the reservoir. Avian exposure to mercury at Lahontan Reservoir was evaluated in both eggs and blood of young snowy egrets (Egretta thula) and black-crowned night-herons (Nycticorax nycticorax). Annual MeHg concentrations in unfiltered water below the reservoir, during the time period (Julian Days 90-190) when birds were present, correlated significantly with mercury concentrations in night-heron blood (r(2 )= 0.461, p = 0.027), snowy egret blood (r(2 )= 0.474, p = 0.024), and night-heron eggs (r(2) = 0.447, p = 0.029), but not snowy egret eggs. A possible reason for lack of an MeHg water correlation with snowy egret eggs is discussed and relates to potential exposure differences associated with the food habits of both species. THg concentrations in water collected below the reservoir were not related to egg or blood mercury concentrations for either species.

Selenium and Metal Concentrations in Waterbird Eggs and Chicks at Agassiz National Wildlife Refuge, Minnesota

Exceptionally high cadmium (Cd) and chromium (Cr) concentrations were reported in eggs, feathers, or livers of selected waterbird species nesting at Agassiz National Wildlife Refuge (Agassiz) in 1994. Ten- to 15-day-old Franklin's gull (Larus pipixcan), black-crowned night-heron (Nycticorax nycticorax), and eared grebe (Podiceps nigricollis) chicks were collected in 1998, 1999, and 2001 at Agassiz and analyzed for selenium (Se) and metals including Cd and Cr. Freshly laid eggs were collected in 2001 from Franklin's gull, black-crowned night-heron, eared grebe, and pied-billed grebe (Podilymbus podiceps) nests at Agassiz. Based on a multivariate analysis, the pattern of Se and metal concentrations differed among species for eggs, chick feathers, and chick livers. Low Cd and Cr concentrations were measured in eggs, chick livers, and chick feathers of all four species. Mercury concentrations in black-crowned night-heron and eared grebe eggs collected from Agassiz in 2001 were lower than concentrations reported in 1994. Se and metal concentrations, including Cd and Cr, in waterbird eggs and chicks collected at Agassiz in 1998, 1999, and 2001 were not at toxic levels.

Heavy metal concentrations in diet and livers of Black-crowned Night Heron Nycticorax nycticorax and Grey Heron Ardea cinerea chicks from Pyeongtaek, Korea

This study presents concentrations of iron, manganese, zinc, copper, lead and cadmium in diet and livers of Black-crowned Night Heron Nycticorax nycticorax and Grey Heron Ardea cinerea chicks from Pyeongtaek, Gyeonggi-do, Korea. Heavy metal concentrations of heron chicks were not related to concentrations in the diet. Copper concentrations were significantly greater in the diet of Black-crowned Night Herons (geometric mean = 13.6 wet microg/g) than Grey Herons (7.45 wet microg/g), other metal concentrations did not differ between the diet of two species. Manganese (respectively 3.20 wet microg/g, 1.41 wet microg/g) and cadmium (respectively 13.4 wet microg/kg, 1.41 wet microg/kg) concentrations were higher in livers of Black-crowned Night Heron chicks than Grey Heron chicks, but zinc, iron, copper and lead concentrations in livers did not differ in between two herons. The essential elements were at background levels, however copper concentrations were relatively higher than previously reported from Korea. Lead and cadmium concentrations were within background levels for herons.

Trace element residues in eggshells of grey heron (Ardea cinerea) and black-crowned night heron (Nycticorax nycticorax) from Nallihan Bird Paradise, Ankara-Turkey

Concentrations of four trace elements (Cd, Ni, Cu and Pb) were determined in eggshells of grey heron (Ardea cinerea) and black-crowned night herons (Nycticorax nycticorax) from Nallihan Bird Paradise, which is located in the northern part of Sariyar Dam Reservoir, Turkey. Results indicated that, within the same area, these ardeid species differed in the levels of Cd, Cu and Pb in their eggshells (generally grey heron > night heron), possibly because females may have foraged in different habitats and regions. Geometric means found for Cd, Ni, Cu and Pb in eggshells were 0.931 mg/kg, 0.405 mg/kg, 6.755 mg/kg and 4.567 mg/kg, respectively, for grey heron; and 0.230 mg/kg, 0.220 mg/kg, 1.369 mg/kg and 1.108 mg/kg, respectively, for night heron. High bioaccumulation from sediments to eggshells occured for Cu and Pb, while Cd and Ni exhibited low accumulation. Bioaccumulation ratios were calculated as 19.63 (Cu) and 22.9 (Pb) in eggshells of grey herons. In conclusion, eggshells of grey herons appeared to be good bioindicators for monitoring of Cu and Pb in Nallihan Bird Paradise.

Clutch Size, Reproductive Success, and Growth Rate of Black-Crowned Night Herons Nycticorax nycticorax

We studied the breeding ecology of Black-crowned Night Herons (Nycticorax nycticorax) in three mixed species heronries in Pyeongtaek, Gyeonggi-Do, Korea during 2000 and 2001. Population size and breeding species changed between 2000 and 2001. Mean clutch size, hatching success and fledging success was not significantly different between years. Fledging success varied significantly in 2000 but not in 2001 with regard to number of hatchlings per nest. Mass, culmen-length, and wing-length growth rates of Black-crowned Night Heron chicks did not differ between years. With regard to hatching order in 2000 and in 2001, only tarsus-length growth rates differed between years. Clutch size, reproductive success, and growth rate of Black-crowned Night Herons did not differ between years.

Waterbirds (other than Laridae) nesting in the middle section of Laguna Cuyutlán, Colima, México

Laguna de Cuyutlán, in the state of Colima, Mexico, is the only large coastal wetland in a span of roughly 1150 km. Despite this, the study of its birds has been largely neglected. Between 2003 and 2006 we assessed the waterbirds nesting in the middle portion of Laguna Cuyutlán, a large tropical coastal lagoon, through field visits. We documented the nesting of 15 species of non-Laridae waterbirds: Neotropic Cormorant (Phalacrocorax brasilianus), Tricolored Egret (Egretta tricolor), Snowy Egret (Egretta thula), Little Blue Heron (Egretta caerulea), Great Egret (Ardea alba), Cattle Egret (Bubulcus ibis), Black-crowned Night-heron (Nycticorax nycticorax), Yellow-crowned Night-heron (Nyctanassa violacea), Green Heron (Butorides virescens), Roseate Spoonbill (Platalea ajaja), White Ibis (Eudocimus albus), Black-bellied Whistling-duck (Dendrocygna autumnalis), Clapper Rail (Rallus longirostris), Snowy Plover (Charadrius alexandrinus), and Black-necked Stilt (Himantopus mexicanus). These add to six species of Laridae known to nest in that area: Laughing Gulls (Larus atricilla), Royal Terns (Thalasseus maximus), Gull-billed Terns (Gelochelidon nilotica), Forster's Terns (S. forsteri), Least Terns (Sternula antillarum), and Black Skimmer (Rynchops niger), and to at least 57 species using it during the non-breeding season. With such bird assemblages, Laguna Cuyutlán is an important site for waterbirds, which should be given conservation status.

Effects of Contaminants on Reproductive Success of Aquatic Birds Nesting at Edwards Air Force Base, California

Contamination by organochlorine pesticides (OCs), polychlorinated biphenyls, metals, and trace elements at Edwards Air Force Base (EAFB), located in the Mojave Desert, could adversely affect nesting aquatic birds, especially at the sewage lagoons that comprise Piute Ponds. Estimates of avian reproduction, in conjunction with analyses of eggs and avian foods for contaminant residues, may indicate the potential for negative effects on avian populations. From 1996 to 1999, we conducted studies at the Piute Ponds area of EAFB to evaluate the impacts of contaminants on nesting birds. Avian reproduction was evaluated in 1999. Eggs were collected for chemical analyses in 1996 and 1999, and African clawed frogs (Xenopus laevis), a likely food source, were collected for chemical analyses in 1998. Avian species occupying the higher trophic levels--black-crowned night-heron (Nycticorax nycticorax), white-faced ibis (Plegadis chihi), and American avocet (Recurvirostra americana)--generally bioaccumulated higher concentrations of contaminants in their eggs. Reproductive success and egg hatchability of night-herons and white-faced ibises in the Piute Ponds were similar to results observed at other western colonies. Deformities were observed in only one embryo in this study, but concentrations of contaminants evaluated in this ibis embryo were considered insufficient to have caused the deformities. Because clawed frogs, a primary prey item for night-herons at Piute Ponds, had no detectable levels of any OCs, it is likely that OCs found in night-heron eggs were acquired from the wintering grounds rather than from EAFB. The presence of isomers of dichlorodiphenyltrichloroethane (DDT) in ibis eggs indicated recent exposure, but invertebrates used for food by ibises were not sampled at Piute Ponds, and conclusions about the source of OCs in ibis eggs could not be made. Concentrations of contaminants in random and failed eggs of individual species were not different, and we concluded that contaminants did not cause the observed egg failures.

Diel activity patterns of presence and absence from a heronry and post-breeding roosts observed in radio-tagged Black-crowned Night Herons Nycticorax nycticorax

ABSTRACT We studied the diel activity patterns of presence and absence from a heronry and post-breeding roosts of ten free-living Black-crowned Night Herons Nycticorax nycticorax in Honshu, Japan. We described their diel activity patterns and examined whether the patterns of individual herons varied while living in a heronry, and whether those patterns changed as the individual lived in the heronry or in a post-breeding roost. Six tagged herons were frequently absent from their heronries during the daytime. There were four distinctive types among the observed diel activity patterns: 1) absence of individual herons observed every other day, 2) presence at the heronry occurred largely after sunrise and before sunset, 3) individuals made many short foraging trips and short visits to the heronry throughout both the day and night, 4) absent only at night (nocturnal) and individuals left the roosting place exactly at sunset every day. The six herons that were absent from the heronry during the daytime varied th...

Seroprevalance and Identification of Influenza A Virus Infection from Migratory Wild Waterfowl in China (2004–2005)

Outbreaks of a highly pathogenic avian influenza (H5N1) were reported in birds in more than eight Asian countries. We sought to identify the origin of this infection, and herein report the results of serological and virological monitoring of migrant wild waterfowl in mainland China. From a total of 493 serum samples, collected from 15 migratory wild waterfowl species for 9 months (from June 2004 to May 2005) in mainland China, we detected only low-level antibodies against influenza subtypes H2, H9 and H10 in the relict gull, little egret, black-crowned night heron, bar-tailed godwit, whimbrel and the common greenshank. No virus was identified from the 1052 cloacal and oropharyngeal swabs except dead bar-headed geese. These data show that the influenza type A virus subtypes H2-H13 did not circulate at detectable levels within the sampled population.