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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↗

USGS2007

Pattern and potential causes of White-faced Ibis, Plegadis chihi, establishment in the northern prairie and parkland region of North America

The Northern Prairie and Parkland Waterbird Conservation Plan calls for renewed attention to determining the current status of waterbird populations, their distributions, and conservation needs. It highlights the need for baseline information on the White-faced Ibis (Plegadis chihi). In response, we examined the historical and current distribution of the ibis in North Dakota and summarized first sightings and nest records for the provinces and other states composing the northern prairie and parkland region. The establishment of breeding colonies of White-faced Ibis here may be due to climate and precipitation patterns, invasion and spread of Narrowleaf Cattail (Typha angustifolia), changes in agricultural practices, habitat loss and range expansion in the southern and western portions of the species' range, and increases in ibis populations in the Intermountain West. We placed special emphasis on North Dakota, a state for which there is scant published information concerning the current status of this species. In recent decades, the ibis has become a regular breeding-season resident in North Dakota and in other areas of the northern prairie and parkland region. From 1882 to 2002, there were 145 reports of one or more White-faced Ibis in North Dakota, including 93 reports during the breeding season (15 May to 31 August), 49 during the non-breeding season (1 September to 14 May), and three for which the season of occurrence was not reported. Prior to the 1960s, there were only three records of the species in North Dakota. Observations of White-faced Ibises in North Dakota increased dramatically between the 1960s and the early 21st century, and the species has been observed nearly annually since 1971. The first White-faced Ibis nesting activity in the state was recorded in 1978, and to date, there have been 21 known records of nesting activity in the state. The species nested in large (>300 ha) semipermanent or permanent wetlands within mixed-species colonies ranging in areal extent from small (0.1 ha) to fairly large (27 ha), and colonies were located in patches of emergent vegetation dominated by cattails (Typha) and bulrushes (Scirpus). We classify the White-faced Ibis as a fairly common migrant and a locally uncommon breeder east of the Missouri River and a casual migrant west of the Missouri River.

Canadian Field-Naturalist↗

USGS1998

Status of the white-faced ibis: Breeding colony dynamics of the Great Basin population, 1985-1997

The status of the White-faced Ibis (Plegadis chihi) in the Great Basin is of concern because of its small population size and the limited and dynamic nature of its breeding habitat. We analyzed existing annual survey data for the White-faced Ibis breeding in the Great Basin and surrounding area for 1985-1997. Methods varied among colonies and included flight-line counts and fixed-wing aircraft and helicopter surveys. The number of White-faced Ibis breeding pairs in the Great Basin area has nearly tripled since 1985, despite years of severe flooding and drought at major breeding areas. This growth is reflected in both peripheral (i.e., Oregon, California, Idaho) and core (i.e., Nevada and Utah) components of the population. Our data on colony dynamics in Oregon and Nevada illustrate the ability of the highly nomadic White-faced Ibis to compensate for poor conditions at traditional colony sites by moving among colonies and rapidly colonizing newly available wetlands. We suggest that the White-faced Ibis would benefit from a landscape mosaic of well-distributed peripheral wetlands and persistent colony sites. The nomadic nature of the White-faced Ibis and the dynamic nature of their breeding habitat necessitates that wetland management decisions and population monitoring be conducted in a regional context.

Colonial Waterbirds↗

USGS1998

Status of the White-faced Ibis: Breeding colony dynamics of the Great Basin population, 1985-1997

Waterbirds↗

USGS2009

Wintering area DDE source to migratory white-faced ibis revealed by satellite telemetry and prey sampling

Locations of contaminant exposure for nesting migratory species are difficult to fully understand because of possible additional sources encountered during migration or on the wintering grounds. A portion of the migratory white-faced ibis (Plegadis chihi) nesting at Carson Lake, Nevada continues to be exposed to dichloro-diphenyldichloro-ethylene (DDE) with no change, which is unusual, observed in egg concentrations between 1985 and 2000. About 45-63% of the earliest nesting segment shows reduced reproductive success correlated with elevated egg concentrations of >4 ??g/g wet weight (ww). Local prey (primarily earthworms) near nests contained little DDE so we tracked the migration and wintering movements of 20 adult males during 2000-2004 to determine the possible source. At various wintering sites, we found a correlation (r 2 = 0.518, P = 0.0125, N = 11) between DDE in earthworm composites and DDE in blood plasma of white-faced ibis wintering there, although the plasma was collected on their breeding grounds soon after arrival. The main source of DDE was wintering areas in the Mexicali Valley of Baja California Norte, Mexico, and probably the adjacent Imperial Valley, California, USA. This unusual continuing DDE problem for white-faced ibis is associated with: the long-term persistence in soil of DDE; the earthworms' ability to bioconcentrate DDE from soil; the proclivity of white-faced ibis to feed on earthworms in agricultural fields; the species's extreme sensitivity to DDE in their eggs; and perhaps its life history strategy of being a "capital breeder". We suggest surveying and sampling white-faced ibis eggs at nesting colonies, especially at Carson Lake, to monitor the continuing influence of DDE.

Ecotoxicology↗

USGS2003

An index of biological integrity (IBI) for Pacific Northwest rivers

The index of biotic integrity (IBI) is a commonly used measure of relative aquatic ecosystem condition; however, its application to coldwater rivers over large geographic areas has been limited. A seven-step process was used to construct and test an IBI applicable to fish assemblages in coldwater rivers throughout the U.S. portion of the Pacific Northwest. First, fish data from the region were compiled from previous studies and candidate metrics were selected. Second, reference conditions were estimated from historical reports and minimally disturbed reference sites in the region. Third, data from the upper Snake River basin were used to test metrics and develop the initial index. Fourth, candidate metrics were evaluated for their redundancy, variability, precision, and ability to reflect a wide range of conditions while distinguishing reference sites from disturbed sites. Fifth, the selected metrics were standardized by being scored continuously from 0 to 1 and then weighted as necessary to produce an IBI ranging from 0 to 100. The resulting index included 10 metrics: number of native coldwater species, number of age-classes of sculpins Cottus spp., percentage of sensitive native individuals, percentage of coldwater individuals, percentage of tolerant individuals, number of alien species, percentage of common carp Cyprinus carpio individuals, number of selected salmonid age-classes, catch per unit effort of coldwater individuals, and percentage of individuals with selected anomalies. Sixth, the IBI responses were tested with additional data sets from throughout the Pacific Northwest. Last, scores from two minimally disturbed reference rivers were evaluated for longitudinal gradients along the river continuum. The IBI responded to environmental disturbances and was spatially and temporally stable at over 150 sites in the Pacific Northwest. The results support its use across a large geographic area to describe the relative biological condition of coolwater and coldwater rivers with low species richness.

Transactions of the American Fisheries Society↗

USGS1989

DDE, selenium, mercury, and white-faced ibis reproduction at Carson Lake, Nevada

We studied organochlorine, mercury (Hg), and selenium (Se) contamination in white-faced ibis ( Plegadis chihi ) nesting at Carson Lake, Nevada, in 1985 and 1986. Dichloro diphenyl dichloroethylene (DDE) was related to fewer young produced/nesting attempt (P = 0.0001), fewer young produced/successful nest (P = 0.0075), and eggshell thinning (P = 0.0001). As DDE in eggs increased to >4 ppm (wet wt), and especially > 8 ppm, productivity decreased significantly (P < 0.05) and the incidence of cracked eggs increased. Assuming that 4 ppm DDE is the critical residue level, 40% of the nesting population in 1985 and 1986 was adversely impacted by DDE, with a net loss of 20% of the population's expected production (to about 10 days old). Most eggs containing exceptionally high DDE levels (8-29 ppm) also had substantial amounts of dichloro diphenyl trichloroethane (DDT), which implies recently-used DDT as the source. No evidence of breeding ground DDE-DDT contamination was found. The white-faced ibis winter in Mexico, and mostly in the interior agricultural region. Concentrations of DDE-DDT in ibis eggs, unlike most other wading bird species from the Great Basin, did not decline during the last decade. Other organochlorine contaminants were generally low and detected in 533% of the eggs. Selenium and Hg were accumulated by ibis on the Nevada breeding grounds, but concentrations in eggs did not reach levels sufficient to impact the production of 7-10 day old young. Potential Se and especially Hg accumulation during the remainder of the summer was high, but actual effects on growing young and adults remain unknown.

Nevada↗

USGS2022

Terrestrial ecosystem modeling with IBIS: Progress and future vision

Dynamic Global Vegetation Models (DGVM) are powerful tools for studying complicated ecosystem processes and global changes. This review article synthesizes the developments and applications of the Integrated Biosphere Simulator (IBIS), a DGVM, over the past two decades. IBIS has been used to evaluate carbon, nitrogen, and water cycling in terrestrial ecosystems, vegetation changes, land-atmosphere interactions, land-aquatic system integration, and climate change impacts. Here we summarize model development work since IBIS v2.5, covering hydrology (evapotranspiration, groundwater, lateral routing), vegetation dynamics (plant functional type, land cover change), plant physiology (phenology, photosynthesis, carbon allocation, growth), biogeochemistry (soil carbon and nitrogen processes, greenhouse gas emissions), impacts of natural disturbances (drought, insect damage, fire) and human induced land use changes, and computational improvements. We also summarize IBIS model applications around the world in evaluating ecosystem productivity, carbon and water budgets, water use efficiency, natural disturbance effects, and impacts of climate change and land use change on the carbon cycle. Based on this review, visions of future cross-scale, cross-landscape and cross-system model development and applications are discussed.

Journal of Resources and Ecology↗

USGS2023

Cryptic tolerant fish species and their potential effect on index of biotic integrity (IBI) scores

Indices such as the Index of Biotic Integrity (IBI) are often used by management agencies to estimate the abstract property of stream health. These indices are usually predicated on the belief that certain fish species are tolerant to environmental perturbation while others are sensitive. Species are usually designated as either tolerant or sensitive in these analyses based on inherent ecological or taxonomic characteristics. However, previous literature has shown that certain species from ecological or taxonomic “sensitive” groups experience increased abundance in degraded streams. We term such species “cryptic tolerants”. Using a stream fish assemblage dataset of 433 unique sample locations across the state of Alabama and the National Landcover Dataset, our objectives were to 1) identify the most common cryptic tolerant species, 2) investigate how cryptic tolerant species might inflate indices of stream health, and 3) compare an alternative measure of stream health in which species are statistically defined rather than defined using the traditional trait-based approach. We identified cryptic tolerants using Nonmetric Multidimensional Scaling in six ecoregions. A series of regressions revealed that the proportion of cryptic tolerant species decreased in response to an increasing proportion of forested land in catchments while the proportion of true sensitives increased in all ecoregions except for the Cumberland Plateau. An index that simply used the percentage of statistically defined, non-tolerant species generally had lower p-values and higher r 2 values than IBI scores when both were regressed against percentage of forest in catchment. However, both indices had low degrees of correlation with expected disturbance, indicating a univariate index may be inadequate to characterize stream health. Our results highlight a potential issue with applying the IBI to diverse southeastern systems in the United States, which may be alleviated by designating species sensitivity based on empirical response to disturbance rather than taxonomic or ecological characteristics.

Alabama↗

USGS2009

Feather mercury concentrations and physiological condition of great egret and white ibis nestlings in the Florida Everglades

Mercury contamination in the Florida Everglades has reportedly played a role in the recent decline of wading birds, although no studies have identified a mechanism leading to population-level effects. We assessed feather mercury levels in great egret (Ardea alba; n = 91) and white ibis (Eudocimus albus; n = 46) nestlings at breeding colonies in the Florida Everglades during a year (2006) with excellent breeding conditions (characterized by hydrology leading to concentrated prey) and a year with below average breeding conditions (2007). We also assessed the physiological condition of those nestlings based on levels of plasma and fecal corticosterone metabolites, and stress proteins 60 and 70. Mercury levels were higher in both species during the good breeding condition year (great egret = 6.25????g/g ?? 0.81 SE, white ibis = 1.47????g/g ?? 0.41 SE) and lower in the below average breeding year (great egret = 1.60????g/g ?? 0.11 SE, white ibis = 0.20????g/g ?? 0.03 SE). Nestlings were in better physiological condition in 2006, the year with higher feather mercury levels. These results support the hypothesis that nestlings are protected from the harmful effects of mercury through deposition of mercury in growing feathers. We found evidence to suggest shifts in diets of the two species, as a function of prey availability, thus altering their exposure profiles. However, we found no evidence to suggest they respond differently to mercury exposure. ?? 2008 Elsevier B.V. All rights reserved.

Science of the Total Environment↗

USGS2020

Nesting ecology of White-faced Ibis (Plegadis chihi) in Great Salt Lake, Utah

We studied the nesting ecology of White-faced Ibis ( Plegadis chihi ) at 3 sites within the Bear River Migratory Bird Refuge, Great Salt Lake, Utah, USA. Ibises built nests in small mounds (mean height = 14.4 ± 4.3 cm) above shallow water (mean depth = 12.0 ± 6.6 cm) located within patchy vegetation (mean percent vegetative cover = 17.2 ± 17.8% vegetative cover) with mean vegetation height of 31.7 ± 9.8 cm. White-faced Ibis typically laid a clutch of 3 or 4 eggs (mean clutch size = 3.08 ± 0.76) and initiated nests over a 50 d period between 24 April 2012 and 12 June 2012. Mean nest success was 38% (95% CI: 31–45%) and hatching success of eggs from successful nests was 76 ± 26%. Although most of the breeding parameters estimated for White-faced Ibis nesting in Utah were comparable to other populations in Oregon and Idaho (USA), nest success may now be lower than has been historically documented.

Utah↗

USGS1997

DDE still high in white-faced ibis eggs from Carson Lake, Nevada

White-faced Ibis (Plegadis chihi) eggs collected in 1996 at Carson Lake, Nevada, showed no decrease in p,p′-DDE (DDE) concentrations from levels in 1985 and 1986 which is contrary to DDE patterns shown for most avian species. An estimated 40-45% of the population was adversely affected by DDE in 1985, 1986, and 1996 with a probable net loss of about 20% of the expected productivity. One segment of the nesting population at Carson Lake in 1996 averaged 18.3% eggshell thinning, although the mean for the whole population is not known. Obvious population declines of White-faced Ibis have not been reported, although quantitative population data are incomplete; however, the excellent and predictable food sources on the breeding grounds in Nevada (due to flood irrigation by farmers) appear to contribute to a high reproductive potential. While adverse consequences of DDE were not documented at the population level, it is important to locate the source(s) of the DDE/p,p′-DDT (DDT). Results of a previous study showed that prey from the breeding grounds were not contaminated with DDE/DDT. The White-faced Ibis DDE/DDT loads are suspected to originate from localized areas on the wintering grounds and/or staging areas. Use of satellite transmitters placed on nesting birds is proposed to locate the source of the DDE/DDT.

Nevada↗

USGS1997

Development of an IBI-based assessment of depressional wetlands in Maryland and Delaware

The hydrogeomorphic approach (HGM) of wetland assessment emphasizes functional components of wetlands such as water storage, transformation and cycling of elements, accumulation of sediments, and preservation of habitats. Many of the elements measured in HGM are physical rather than ecological or biological. The HGM approach, therefore, provides information on certain aspects of wetlands and omits other aspects. In contrast, the Index of Biological Integrity (IBI) approach focuses on biological components of wetlands such as species richness, the presence or proportion of certain 'indicator' species, representation of different trophic levels, and measures of wildlife or fish health. Here too, some aspects of a wetland are omitted and others not covered by HGM are included. We contend that these differences in focus add strengths and weaknesses to each method. This paper reviews progress on the development of IBIs for restored depressional wetlands in the Mid-Atlantic States, especially Maryland and Delaware. During our first field season we identified 25 wetlands ranging from 1-10 acres, most of which were restored with federal, state, and private landowner cooperation over hydric soils. Separate IBIs are being created for macrophytes, macroinvertebrates, amphibians, and data on mammal and avian populations are being collected. Simultaneously, chemical and physical data are being collected on water DO, turbidity, temperature, conductivity, nitrates, ammonia, chlorophyll, pH; soil metal levels and texture; and wetland size, configuration, hydrology, drainage area, and surrounding land use.

Book chapter↗

USGS1990

Comparison of breaking strength and shell thickness as evaluators of white-faced ibis eggshell quality

Data from a 1986 field study of white-faced ibis ( Plegadis chihi ) nesting at Carson Lake, Nevada, were used to compare the utility of eggshell strength measurement and eggshell thickness as indicators of eggshell quality. The ibis population had a history of reproductive failure correlated with elevated egg concentrations of p, p '-DDE, hereafter referred to as DDE. Eggs from 80 nests (one egg/nest) were tested for shell strength and thickness. Egg contents were analyzed for organochlorines, mercury and selenium; productivity at each nest (minus one egg) was monitored in the field. DDE-DDT concentrations in the eggs ranged from none detected (<0.1) to 29 ppm (wet weight). Shell thickness and shell strength were both negatively correlated with DDE (−0.60, −0.61, respectively), but shell strength deteriorated at a faster rate than shell thickness. Scanning electron micrographs indicated the deterioration in strength was related to changes in ultrastructure as well as to decreased thickness. Fourteen eggs with <0.40 ppm DDE were used to exemplify normal “control” eggs. Of the eggs with higher concentrations of DDE (i.e., ≥0.40 ppm), 11 of 66 were thinner (>2 SD below “control” mean) than normal, 11 of 59 were weaker than normal and 7 eggs were cracked so their strength could not be tested, although thickness was measured. Therefore, 17% of the eggs with ≥0.40 ppm DDE were thinner than normal and 27% were either weaker than normal or cracked. Further, six eggs (four with ≥15 ppm DDE) did not have abnormally thin shells, but did have abnormally weak shells. Nests with abnormal test eggs (thinner, weaker or cracked) produced fewer young than nests with normal eggs. Use of the shell strength parameter provides additional information for better evaluations of reproductive problems. The potential utility of monitoring eggshell quality goes beyond evaluating effects of organochlorines since recent work indicates that other environmental hazards can affect shell quality.

Environmental Toxicology and Chemistry↗

USGS1972

Pesticide mortality of young white-faced ibis in Texas

The combination of the symptoms observed in sick and dying birds and the high brain residues in the three birds collected dying, as well as in two of the four collected dead, implicate dieldrin as at least one of the causes of mortality of young ibis at the Lavaca Bay colony. Mercury residues in the kidneys of all four dead young, including those with low brain residues of dieldrin, suggest that birds were exposed to mercury in rice fields and that mercury may also have contributed to the mortality. Since adult ibis normally feed their young on invertebrates collected in rice fields treated with aldrin and Ceresan L, the use of these rice pesticides appears to be a serious hazard to this species, and probably to other wild birds with similar habits.

Texas↗

USGS2021

Egg morphometrics and egg shape coefficients for White-faced Ibis (Plegadis chihi)

Egg size is a useful metric for maternal investment, offspring quality, and contaminant studies. Yet these values and the egg shape coefficients required to estimate egg size are not available for many species, including White-faced-Ibis ( Plegadis chihi ). We provide egg morphometrics derived from 319 White-faced Ibis eggs sampled at Bear River Migratory Bird Refuge, Great Salt Lake, Utah, from 2010 to 2012. Measured egg length (mean ± SD) was 51.20 ± 1.99 mm, egg width was 36.08 ± 1.15 mm, and whole egg mass was 34.1 ± 3.3 g. Estimated whole egg volume was 34.63 ± 3.73 cm 3 and estimated egg shape coefficients were 0.507 for K v (whole egg and egg contents), 0.547 for K w (whole egg), and 0.524 for K w (egg contents only). In addition, we documented expected declines in egg mass over time due to incubation (–0.22 g/d) and desiccation during storage (–0.03 g/d), that should be accounted for prior to analyses that use egg mass of freshly laid eggs.

Utah↗

USGS1957

Eastern glossy ibis nesting in southeastern Maryland

On June 25, 1956, Don P. Fankhauser and I investigated a large heron colony of mixed species, on Mills Island in Chincoteague Bay, Worcester County, Maryland. Large numbers of American Egrets ( Casmerodius albus ), Snowy Egrets ( Leucophoyx thula ), Louisiana Herons ( Hydranassa tricolor ), Little Blue Herons ( Florida caerulea ), and Black-crowned Night Herons ( Nycticorax nycticorax ) were found, all nesting in a dense grove of young red cedar ( Juniperus virginiana ). Much to our surprise, the colony also included at least two pairs of the Eastern Glossy Ibis ( Plegadis falcinellus ). Four adults of this species were repeatedly observed flying low overhead and frequently perching in nearby tree-tops. In addition, two young ibis, about three-fourths grown, were found. These two birds, still unable to fly, would hop and flutter among the tree branches whenever they were approached too closely. The large white crown patch and the peculiar barred markings of the bill were especially noticeable on both of the young.

Maryland↗

USGS1980

White-faced ibis populations and pollutants in Texas, 1969-1976

Eggshell thickness, levels of pollutant residues, and population status of the white-faced ibis (Plegadis chihi) were monitored in Texas from 1969 through 1976. Texas ibis nesting populations declined by 42%. Reproductive success apparently was limited by DDE-induced shell thinning and by dieldrin-caused mortality. Eggshells averaged 4% to 10% thinner than the pre-1943 mean thickness. Shells of numerous crushed eggs exceeded 20% thinning. Mean DDE residues in randomly collected eggs decreased from 0.94 ppm in 1970 to 0.25 ppm in 1976. DDE was higher, averaging 2.5 ppm, in thin-shelled eggs. DDE was negatively correlated with shell thickness. Dieldrin and PCB residues increased slightly from 1970 to 1976, but neither was correlated significantly with shell thickness. Residues in brains of many dead and dying ibises collected during years of extreme reproductive failure, 1970 and 1973, contained between 5 and 25 ppm dieldrin. Ibises were exposed to aldrin and dieldrin by feeding in rice fields where aldrin-treated rice seed was planted. Improved nesting success in 1976 may have been related to declining residues of DDE and to the discontinued use of aldrin in rice fields.

Southwestern Naturalist↗