Plegadis Chihi Research Articles

Transboundary pollution: Persistent organochlorine pesticides in migrant birds of the Southwestern United States and Mexico

AbstractThe hypothesis that migratory birds accumulate persistent organochlorine pesticides (POPs) during the winter in Latin America has been prevalent for many years, particularly since 1,1,1‐trichloro‐2,2–bis(p‐chlorophenyl)ethane (DDT) was banned in the United States in 1972. It has been suggested that peregrine falcons (Falco peregrinus), black‐crowned night herons (Nycticorax nycticorax), white‐faced ibises (Plegadis chihi), various migratory waterfowl and shorebirds, and other avian species accumulate higher concentrations of POPs while on migration or on their wintering grounds in Latin America. Nonetheless, the data obtained thus far are limited, and there is no clear pattern to suggest that such accumulation occurs on a widespread basis. In this review wildlife contaminant studies conducted along the U.S.‐Mexico border and throughout Mexico are discussed. The results for the most part seem to indicate that no major accumulation of 2,2‐bis(p‐chlorophenyl)‐1,1‐dichloroethylene) (DDE), the most persistent organochlorine compound, has occurred or been reported for most parts of Mexico. The majority of the DDE values in birds from Mexico were similar to those reported in birds from the southwestern United States during the same years. More work needs to be done, particularly in those cotton‐producing areas of Mexico where DDT was applied heavily in the past (e.g., Chiapas and Michoacan). Because DDT is still used for malaria control and may still be used in agriculture in Chiapas, this state is probably the one where most migrant species would still be at a significant risk of increased accumulation of DDE and DDT.

Foraging Behavior of White-Faced Ibises (Plegadis chihi) in Relation to Habitat, Group Size, and Sex

Foraging Behavior of White-Faced Ibises (Plegadis chihi) in Relation to Habitat, Group Size, and Sex

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

AbstractData 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.

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, fewer young produced/successful nest and eggshell thinning. As DDE in eggs increase to >4ppm (wet wt), and especially >8ppm, productivity decreased significantly 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 poplation'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. Concentration 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 {le}33% of the eggs. Selenium and Hg were accumulated by ibis on the Nevada breeding grounds, but concentrationsmore » 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.« less

Organochlorine Contaminants in White-Faced Ibis Eggs in Southern Texas

-White-faced Ibis (Plegadis chihi) eggs collected from two colonies in southern Texas in 1985 had low mean concentrations of DDE (0.14-0.27 ppm wet weight). 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 (1.0 ppm) than in eggs collected from nests where all the remaining eggs hatched (0.15 ppm). Received 20 April 1988, accepted 28 August 1988.

Feeding Ecology of White-Faced Ibises in a Great Basin Valley, USA

-We studied feeding-site characteristics of agricultural fields selected by White-faced Ibises (Plegadis chihi) at Lahontan Valley, Nevada, USA. Feeding-site characteristics considered were field types, field size, soil types, vegetation height, irrigation, water depth, and proximity to the nesting colony. Ibises had a greater preference for alfalfa fields and less preference for corn, wheat-barley, pastures, and oat fields. Greater preferences were also found for fields that were closer to the colony, larger in size, having clay and clay-loam soils, and irrigated. We found no clear preference for vegetation height or water depth. Irrigation water was present at virtually all (99.9%) feeding-sites. Earthworms, the principal prey item found in 16 White-faced Ibis esophagi, were made available to ibises because of irrigation. We show that irrigated fields are valuable feeding habitat for White-faced Ibises.

Trends and Effects of Organochlorine Residues on Oregon and Nevada Wading Birds, 1979-83

-The incidence of DDT (parent compound) declined significantly in the eggs of Blackcrowned Night-Herons (Nycticorax nycticorax), White-faced Ibis (Plegadis chihi), and Black-necked Stilts (Himantopus mexicanus), and showed a downward trend in Snowy Egrets (Egretta thula). Mean DDE residues (breakdown product of DDT) in eggs declined significantly in Black-crowned NightHerons and showed a downward trend in Black-necked Stilts and Snowy Egrets; however, no trend was apparent for White-faced Ibis. Some night-herons, egrets, and ibis laid thin-shelled eggs that cracked; eggshell thickness was negatively correlated with DDE residues in the egg contents. Ibis were the most sensitive species to DDE-induced shell thinning. Generally, reduced reproductive success for ibis started at lower DDE egg residues (3 ppm) than for either Snowy Egrets (5 ppm) or night-herons (8 ppm). Egg residue profiles, band recoveries, biotelemetry studies, and residues in fish and other prey items implicate the southwestern United States (a wintering area) as an important source of DDT-DDE that caused the most serious reproductive problem encountered during the study (in night-herons nesting at Ruby Lake, Nevada). Available evidence indicates that the three other species, together with night-herons from Oregon and Idaho, winter in Latin America.

White-Faced Ibis Nesting in the Southern San Joaquin Valley of California

White-Faced Ibis Nesting in the Southern San Joaquin Valley of California

Effects of Pesticides on Reproductive Success of White-Faced Ibis in Utah, 1979

Effects of Pesticides on Reproductive Success of White-Faced Ibis in Utah, 1979

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. Eggshell thinning has been detected in a number of declining species of fish-eating birds in the United States (Hickey and Anderson 1968, Blus 1970, Anderson and Hickey 1972, Blus et al. 1979). Laboratory investigations have shown that DDT or its metabolites, primarily DDE, induced shell thinning in susceptible species at concentrations found in some wild birds and their eggs (Heath et al. 1969, Wiemeyer and Porter 1970, Haegele and Hudson 1973). The recent population decline in the brown pelican (Pelecanus occidentalis) and the apparent decline in the white-faced ibis (Plegadis chihi) on the Texas Gulf Coast (King et al. 1977, 1978) prompted us to study the extent of eggshell thinning and the impact of organochlorine and heavy metal contamination on these species. The present paper presents information on eggshell thickness changes and chemical resi-

Neottialges (Pelecanectes) ibisicola sp. n. (Acari: Hypoderidae) from the Subcutaneous Tissues of the White-Faced Ibis, Plegadis chihi (Ciconiiformes: Threskiornithidae)

Neottialges (Pelecanectes) ibisicola sp. n. is described from the subcutaneous tissues of the White-faced Ibis, Plegadis chihi, from west Texas. The new species is similar to N. (P.) plegadicola Fain, but differs from this and other species of the subgenus by idiosomal chaetotaxy, presence of a bifurcate apical extension on Tarsus III, solenidion phi on Tibia I less than 1/2 as long in the new species, lateroventral seta of Tibia I whiplike, structure of the genital sclerite and suckers, and presence of punctations on the dorsal idiosoma. The morphology and host-parasite relationships of the new species are compared with those of related species of hypopi from the host family Threskiornithidae.

DDE residues in blood and other tissues of white-faced ibis

Adult white-faced ibis were collected three times during the nesting season to study the relationship of DDE levels in blood and in subcutaneous fat and breast muscle. DDE residues in blood serum were strongly related to DDE levels in both fat and breast muscle lipids. Residues of DDE varied significantly throughout the season in all tissues sampled. This variation was associated with the seasonal cycle of body fat mobilisation and accumulation. Males apparently utilised more fat during the nesting season than did females and consequently had higher levels of DDE in the blood. Blood samples from white-faced ibis may be used to monitor body burdens of DDE provided variation due to seasonal fat deposition is eliminated.

White-Faced IBIS at Last Mountain Lake, Saskatchewan

White-Faced IBIS at Last Mountain Lake, Saskatchewan

White-Faced IBIS and Cattle Egret at Little Quill Lake

White-Faced IBIS and Cattle Egret at Little Quill Lake

Evaluating the Impact of Pesticides on the White-Faced Ibis in Utah

Evaluating the Impact of Pesticides on the White-Faced Ibis in Utah

Colony and Nest Site Selection in White-Faced and Glossy Ibises

The factors determining colony and nest site selection in the White-faced and Glossy Ibises (Plegadis) were examined from 1972 through 1975. White-faced Ibises were studied in Texas and Argentina, Glossy Ibises in New Jersey and New York. White-faced Ibises generally nest in tule marshes, infrequently on dry land. In selecting a dry land site, White-faced Ibises preferred to nest on the ground among low shrubs and in mixed forbs rather than in habitats containing grass and cactus. Glossy Ibises' habitat varies from Phragmites, Iva, and Smilax to other low shrubs. They did not always nest on the ground. White-faced Ibises nested next to conspecifics, whereas in Glossy Ibises the choice of nearest neighbor was random with respect to the species present. The mean distance to the nearest neighbor was generally less for Glossy Ibis when compared to White-faced Ibis. The space around nests that was devoid of any other nest was examined graphically. Nearest neighbors were farther away when they were on the same level than when the nearest neighbor was above the nest being examined for both species. The visibility index from the nests of Glossy and White-faced Ibises was low, and was less than the mean visibility index for heron and egret species nesting in the same colonies. Visibility was less in the direction of the closest nest compared to that in other directions for all colonies examined. In some colonies, the visibility index in the direction of the closest nest was directly related to the distance to the closest nest. Glossy Ibises nested in denser habitats than did White-faced Ibis, and this was reflected in lower visibility indices for Glossy Ibis. Possible reasons for the recent range changes in the two Plegadis species are discussed.

Spread-wing sunbathing by juvenile White-faced Ibis

Spread-wing sunbathing by juvenile White-faced Ibis

New Seasonal and Distributional Records of Idaho Birds

White-faced Ibis. Plegadis chihi. Summer resident, with earliest spring records on 14 May 1963 and 12 May 1964. Approximately 250 ibis were found on the Minidoka National Wildlife Refuge in 1963 (primarily in Blaine County), and 100 in 1964. About 25 nests had eggs on 29 May 1963, and about 20 nests were located in the same area on 25 May 1964. .The earliest nestlings were seen 14 June 1964. Burleigh (1972) did not list any Idaho breeding records for this species.

Vagrancy of Neotropical Cormorant, Egrets, and White-Faced Ibis

Vagrancy of Neotropical Cormorant, Egrets, and White-Faced Ibis

White-faced Ibis photographed in British Columbia

White-faced Ibis photographed in British Columbia