Mycteria Americana Research Articles

Organochlorine Disaster in Florida—2 Years Later

In late 1996, a major wetlands restoration project was announced, designed to enhance fish and wildlife habitat in 13000 acres of drained wetlands.1,2 Restoration of the wetlands, drained during the 1940s for farming, would help improve water quality of Lake Apopka, Florida's fourth largest lake. The lake had degraded over 50 years, as farms in the former marshes had generated nutrient-rich discharges that fouled the lake.3 Among the species expected to benefit from the restoration were the federally endangered wood stork (Mycteria americana) and whooping crane (Grus americana), the federally threatened bald eagle (Haliaeetus leucocephalus), and the state threatened sandhill crane (Grus canadensis).' Muck farms were purchased on the north shore of Lake Apopka and farm production ceased at the sites.2 In the summer of 1998, 6000 acres were flooded and the former farms were covered

Nocturnal Activities of Post-breeding Wood Storks

Abstract Postbreeding season activities of Wood Storks (Mycteria americana) were examined during 24 h long observation periods at inland impoundments and a coastal roost site. Storks were present at inland impoundments and foraged more at night there than at other times of the day. Wood Stork attendance at the coastal roost site was significantly reduced during nocturnal low tides than during daytime low tides or at either period of higher tide levels. Presumably, storks were leaving the roost to forage on fish concentrated in tidal creeks by dropping tides. Nocturnal foraging in freshwater and estuarine systems may be an advantageous strategy for the tactile-feeding storks by reducing the likelihood of their being observed by their prey and possibly by reducing competition with other wading birds. Also, some prey species in both freshwater and saltwater environments are more active nocturnally than diurnally, this increasing their likelihood of capture by nocturnal-foraging Wood Storks. In the coastal setting, low tide events (two per ∼24 h) typically provide at least one “pulse” of stork prey in draining tidal creeks during the nocturnal period.

Nocturnal Activities of Post-Breeding Wood Storks

Nocturnal Activities of Post-Breeding Wood Storks

Nocturnal Activities of Post-breeding Wood Storks

Postbreeding season activities of Wood Storks (Mycteria americana) were examined during 24 h long observation periods at inland impoundments and a coastal roost site. Storks were present at inland impoundments and foraged more at night there than at other times of the day. Wood Stork attendance at the coastal roost site was significantly reduced during nocturnal low tides than during daytime low tides or at either period of higher tide levels. Presumably, storks were leaving the roost to forage on fish concentrated in tidal creeks by dropping tides. Nocturnal foraging in freshwater and estuarine systems may be an advantageous strategy for the tactile-feeding storks by reducing the likelihood of their being observed by their prey and possibly by reducing competition with other wading birds. Also, some prey species in both freshwater and saltwater environments are more active nocturnally than diurnally, this increasing their likelihood of capture by nocturnal-foraging Wood Storks. In the coastal setting, low tide events (two per ∼24 h) typically provide at least one “pulse” of stork prey in draining tidal creeks during the nocturnal period.

Foraging ecology of the endangered wood stork recorded in the stable isotope signature of feathers.

Down feathers and regurgitant were collected from nestling wood storks (Mycteria americana) from two inland and two coastal breeding colonies in Georgia. The stable isotopic ratios of carbon (13C/12C) and nitrogen (15N/14N) in these materials were analyzed to gain insights into the natal origins of juvenile storks and the foraging activities of adults. Down feathers differed in δ13C between inland and coastal colonies, having average isotopic values that reflected the sources of carbon fixed in biomass at the base of the food web. Feathers from the inland colonies differed between colonies in δ15N, while those from the coastal colonies did not. These patterns primarily reflected the foraging activities of parent storks, with individuals capturing differing percentages of prey of distinct trophic status at each colony. Collectively, the carbon and nitrogen isotopic signatures of feather keratin were used to distinguish nestlings from each colony, except for instances where storks from different colonies foraged in common wetlands. The stable isotopic composition of food items in regurgitant was used to reconstruct the trophic structure of the ecosystems in which wood storks foraged. Predicted foraging activities based on the isotopic composition of keratin were generally consistent with the percentage of prey types (freshwater vs. saltwater and lower trophic level vs. upper trophic level consumer) observed in regurgitant, except for the coastal colony at St. Simons Island, where the δ13C of feathers strongly suggested that freshwater prey were a significant component of the diet. This inconsistency was resolved by aerial tracking of adults during foraging excursions using a fixed-wing aircraft. Observed foraging activities supported interpretations based on the stable isotope content of feathers, suggesting that the latter provided a better record of overall foraging activity than regurgitant analysis alone. Observed foraging patterns were compared to the predictions of a statistical model that determined habitat utilization based on habitat availability using a geographic information system (GIS) database. Observed foraging activities and those predicted from feathers both suggested that some adult storks preferred to feed their young freshwater prey, even when saltwater resources were more accessible in the local environment. This conclusion supports the contention that wood stork populations are sensitive to changes in the distribution of freshwater habitats along the southeastern coastal plain of the United States.

First karyotypical description of two American Ciconiiform birds, Mycteria americana (Ciconiidae) and Platalea ajaja (Threskiornithidae) and its significance for the chromosome evolutionary and biological conservation approaches

The karyotypes of Mycteria americana (Ciconiidae) and Platalea ajaja (Threskiornithidae) are described. Both species have a diploid number of 2n = 72. There are slight chromosome morphology differences, which could be related to distinct chromosome evolution pathways of these two families. Besides a better understanding of the chromosome relationships among Ciconiiformes, this first chromosome characterization of M. americana and P. ajaja is an important tool for the conservation of both species.

Aves acuáticas del estero La Manzanilla, Jalisco, México

Con la finalidad de conocer la distribución temporal y el uso del hábitat por las especies de aves acuáticas costeras del estero La Manzanilla, Jalisco, México, se realizaron censos mensuales de marzo de 1997 a febrero de 1998, excepto septiembre. En las once visitas realizadas en el estero se observó un total de 4180 aves (95.24% residentes y 4.76% migratorias), distribuidas en 45 especies (29 residentes y 16 migratorias). Las aves migratorias y residentes presentaron fluctuaciones estacionales en su abundancia; en el primer grupo la mayor abundancia se observó en enero y febrero y estuvo determinado principalmente por la presencia del Cormorán Bicrestado (Phalacrocorax auritus) y el Petrel Mínimo (Oceanodroma microsoma), mientras que en el segundo grupo las mayores abundancias fueron observadas en marzo y junio, y en todos los casos fueron influenciadas por el Cormorán Neotropical (Phalacrocorax brasilianus) y la Cigüeña Americana (Mycteria americana). El estero no fue un paradero importante para las aves migratorias. Sin embargo, para las aves residentes fue apostadero durante la mayor parte del año.

Low Levels of Genetic Variability in North American Populations of the Wood Stork (Mycteria americana)

The breeding population of Wood Storks (Mycteria americana) in the southeastern United States has declined since the 1930s, resulting in the listing of all United States populations of the species as endangered in 1984. We assessed genetic structure within and among nine colonies of Wood Storks from Georgia and Florida. Levels of band sharing based on multilocus oligonucleotide DNA fingerprinting of individuals from seven colonies ranged from 58% among nests within the same tree to approximately 55% within the same colony. Levels of band sharing were similar to those reported for other populations of birds that have experienced drastic reductions in population size. A more thorough analysis of four polymorphic microsatellite loci for 136 individuals from nine colonies indicated low levels of allelic diversity and low genetic divergence among colonies. Genetic differentiation (F ST = 0.015) was similar to levels detected from allozymes for 15 colonies of Wood Storks in Florida (F ST = 0.019). These data, together with demographic studies of these populations, indicated high levels of gene flow among colonies (N m = 16.4). In agreement with previous studies, we recommend that all colonies of Wood Storks in the southeastern United States be managed on a regional basis as a single interbreeding population. Similar genetic surveys of the disjunct breeding populations of Wood Storks in South America and Central America would be beneficial in understanding the total genetic differentiation in the species.

Managing Fish and Invertebrate Resources in a Wood Stork Feeding Pond

ABSTRACT We monitored densities and growth of juvenile bluegills (< 45 mm sl) stocked in autumn into a coastal Georgia freshwater pond that was managed as a wood stork feeding habitat. Cage experiments were used to examine how fish stocking rates and detrital supplements affected fish survival, fish growth, and the availability of invertebrate food supplies. As fish became large enough (> 50 mm standard length) to be useful wood stork food, the majority sought refuge in beds of vegetation and were thus not readily available to storks until July when a complete drawdown concentrated them in residual water. Bluegill growth and survival were not affected by detrital supplements or fish stocking rates (even as high as 450,000/ha). However, detrital hay supplements increased densities of tadpoles and most invertebrates. Fish density did not significantly affect invertebrate abundance.

Dietary Exposure to Mercury in Nestling Wood Storks (Mycteria americana) in Georgia

The United States breeding population of the wood stork (Mycteria americana) was listed as endangered in 1984; the U.S. Fish and Wildlife Service has listed the determination of potential contaminant hazards as a task important to the recovery of the species. Storks nest in colonies and adult storks forage over wide areas and return with prey items to feed to nestlings. The most recently consumed prey items are usually regurgitated by nestlings when they are handled. In 1995, over 200 food items from four wood stork colonies were collected while banding nestlings between 20 and 40 days old, and total mercury determined in individual food items. Two colonies were located on the Atlantic coast and two in inland areas. Overall dietary mercury concentration for each colony was calculated based on the biomass of each type of food item within the diet. Freshwater prey items had higher mercury concentrations than saltwater items most frequently chosen by storks. Daily Hg doses were estimated for a range of nestling sizes and daily food consumption rates. Risk factors were calculated based on two lowest observable adverse effect concentrations (LOAECs) from previous avian mercury ingestion studies. Based on one LOAEC, all four colonies in this study were at risk of sublethal effects due to mercury in the diet of nestling wood storks. More extensive studies of sublethal effects in avian species from mercury contamination are necessary for more accurate risk assessment.

The occurrence of Rhodnius prolixus Stal, 1859, naturally infected by Trypanosoma cruzi in the state of Rio de Janerio, Brazil (Hemiptera, Reduviidae, Triatominae).

Rhodnius prolixus, one of the most importantvector of Chagas’ disease in Venezuela, was ba-sically considered in this country as related to thedomiciliar transmission cycle (O Cova-Garcia etal. 1959 Publ Div Malariol 11: 209-253). In thesylvatic environment it was observed that this spe-cies was mainly adapted to palm tree crowns andnests of Mycteria americana . R. prolixus is a veryeclectic species feeding on marsupials, rats, birdsand reptilians. Moreover, it is agreed that the ad-aptation of R. prolixus to human dwellings was aconsequence of human colonization of the naturalfoci of Trypanosoma cruzi (F Pifano1973 ArchVenezol Med Trop Parasitol Med 5: 3-29).During a search for triatomids performed in anAtlantic rain forest area in Teresopolis, State ofRio de Janeiro, we collected a total of 23 speci-mens (2 adults and 21 nymphs) of R. prolixus fromwhich 13 were infected by T. cruzi . Eleven nymphswere found in the axils of Pteridophyta leaves; 2adults and 4 nymphs in leafages, probably opos-sum nests and 6 nymphs were collected on the trunkof palm-tree. Several eggs could be found in theaxils of 1 Pterydophyta (Fig. 1). The studied area, Granja Florestal, Teresopolis,can be characterized as a secondary rain forest withpoor human dwellings on the forests borders. Thelocal population live basically on small agricul-ture and hunting. Weekly searches were performedbetween September and March (1994-95) and in-cluded palm-trees, bracts of pteridophyta, bird andmammal nests, leafages and bromeliaceae. The collected insects were maintained in glassflasks, fed through a membrane (ES Garcia et al.1975 Rev Brasil Biol 35 : 207-210) and the nymphswere allowed to moult. Seven isolates of T. cruziwere obtained through inoculation of swiss micewith the feces of the infected bugs. Axenic me-dium derived metacyclic forms (10

Hematozoa in the endangered wood stork from Georgia.

Thin blood smears of 75 wood storks (Mycteria americana) from Georgia (USA) were made during the summers of 1994-96 and examined for blood parasites. Haemoproteus crumenium was found in one of 71 juveniles and in two adults from a sample of two subadults and two adults. Intensity of infection in the juvenile and in each of the two adults was 11, 3, and 2 parasites/5,000 erythrocytes, respectively. This is the first record of H. crumenium in the wood stork from Georgia and the second published record of H. crumenium infecting this host in North America. Additionally, one juvenile was infected with a microfilarid.

Foraging Habitat Use by Wood Storks Nesting in the Coastal Zone of Georgia, USA

-We studied foraging habitat use of Wood Storks (Mycteria americana) from three coastal colonies using United States Fish and Wildlife Service National Wetlands Inventory data within a geographic information system (GIS). Observers followed storks from breeding colonies to foraging sites in a fixed-winged aircraft. The main objectives of the study were to estimate the foraging range of each Wood Stork colony, determine what wetland types were used in relation to their availability and spatial distribution, and determine how foraging habitat use was related to tidal stage. Storks foraged in tidal creeks during lower tide levels when prey were concentrated in shallower water, and foraged more in palustrine (freshwater) wetlands when tide levels were high. Predictability of foraging habitat use based on habitat distribution varied among colonies and depended on how wetland types were aggregated. Foraging locations were spatially clustered, in some cases by habitat type (estuarine vs. palustrine). These spatial clusterings may be explained by the proximity of a foraging location to the colony and by the habitat types around the colony. Storks also flew longer distances to forage in palustrine sites than in estuarine sites. Received 29 July 1997, accepted 1 January 1998.

Food of Nestling Wood Storks in Coastal Georgia

Food of Nestling Wood Storks in Coastal Georgia

Seasonal Variation in the Foraging Ecology of the Wood Stork in the Southern Llanos of Venezuela

The southern llanos of Venezuela are tropical wet savannas distinguished by a severe flood-drought alternation throughout the year. I analyzed the seasonal variation in use of habitat, foraging behavior and diet exhibited by the Wood Stork (Mycteria americana) in response to the changing conditions of this environment. With the beginning of the rainy season, streams and lagoons overflowed and inundated extensive marshes, which became the preferred foraging sites for storks. Amphibians and aquatic invertebrates proliferated in these flooded areas and accounted for half of the food consumed; the remaining half was composed of fish. The Wood Stork population was dispersed over the widely inundated area, and individuals foraged solitarily or in small groups. Groping and foot-stirring were the most common foraging behaviors. These patterns changed gradually with the cessation of rains. Shallow marshes dried up rapidly and became inadequate as feeding sites. Wood Storks then formed large foraging aggregations in the few ponds and lagoons that still kept water, where they foraged by groping together in close proximity. Fish accounted for more than 99% of the diet of Wood Storks during the dry season. n. Los llanos inundables de Venezuela son sabanas tropicales humedas caracterizadas por una marcada alternancia inundacion-sequia a lo largo del ano. Se analizaron las variaciones estacionales exhibidas por el Gaban (Mycteria americana) en cuanto a seleccion de habitat, comportamiento alimentario y dieta, como respuesta a las condiciones cambiantes del medio. Con la llegada de las primeras lluvias, los canos y lagunas se desbordaron inundando los esteros, que se convirtieron en los habitats mas frecuentados por los Gabanes. Los anfibios e invertebrados acuaticos proliferaban en estas areas inundadas y constituyeron la mitad de la dieta consumida, estando el resto compuesto por peces. La poblacion de Gabanes estaba dispersa y los individuos se alimentaban en solitario o en pequenos grupos. El tanteo y el pateo fueron las pautas de forrajeo mas utilizadas. Todos estos patrones cambiaron gradualmente con el cese de las lluvias. Los bajios y esteros se secaron rapidamente convirtiendose en lugares inadecuados para la alimentacion. Los Gabanes comenzaron entonces a formar grandes bandadas en los escasos prestamos y lagunas que todavia mantenian algo de agua, donde forrajeaban tanteando juntos en estrecha proximidad. Los peces representaron mas del 99% de la dieta consumida por los Gabanes durante la epoca de sequia.

NONLINEAR POPULATION DYNAMICS OF SIX SPECIES OF FLORIDA CICONIIFORMES ASSESSED BY CHRISTMAS BIRD COUNTS

We analyzed 30 years of Christmas Bird Count (CBC) data for Florida populations of six species of wading birds: Great, Cattle, and Snowy Egrets; Little Blue and Tricolored Herons; and the Wood Stork, a federally listed endangered species. These species are conspicuous components of wetland ecosystems, and the target of numerous management efforts in the state and region. The nonlinear dynamics of these populations were assessed through time series of birds seen during volunteer-based surveys and the first differences of successive annual counts, autocorrelations, and two new metrics: cor- relation time and a momentum oscillator. CBCs have the advantage of being conducted regularly over a large geographic scale. When properly analyzed, CBCs are among the few available sources of reliable population information for small, dark-plumaged species such as Little Blue and Tricolored Herons. Population trends assessed for all species by CBCs paralleled the known or suspected trends determined by breeding-season aerial and ground surveys, conducted by professional biologists. Cattle Egret populations have declined fol- lowing rapid expansion through the 1960s and 1970s; Snowy Egret and, to a lesser extent, Tricolored Heron populations have declined throughout the study period; Little Blue Heron and Great Egret numbers have been relatively stable. Wood Storks, following a period of decline that lasted into the mid-1970s, slowly recovered through the 1980s. Only Cattle Egrets displayed strongly deterministic population dynamics, indicating that predictions of population trends for the other species will require stochastic models with broad confidence bands.

Measurement of wetland hydroperiod using harmonic analysis

The pattern of water-level fluctuations in a wetland is its hydroperiod. Characterization of this pattern cannot be accomplished by measuring a single parameter, but some means of measuring hydroperiod is needed so that comparisons can be made both between wetlands and within a single wetland over time Harmonic analysis can be used to characterize hydroperiod quantitatively by obtaining the amplitude and timing of the dominant periodic component in a time series of water levels. The utility of this method is demonstrated by investigating the link between water management in South Florida and nesting failure by wood storks in the Everglades wetland. With the quantitative measures of hydroperiod derived by harmonic analysis, I am able to demonstrate statistically the relationships between water management and hydroperiod in the Everglades and between hydroperiod and the probability of nesting failure. The simplicity and directness by which these results are achieved suggests the potential for harmonic analysis of hydroperiod as a general tool for wetland science.

Philopatry and Nomadism: Contrasting Long-Term Movement Behavior and Population Dynamics of White Ibises and Wood Storks

Philopatry and Nomadism: Contrasting Long-Term Movement Behavior and Population Dynamics of White Ibises and Wood Storks

Breeding success and chronology of Wood Storks Mycteria americana in northern and central Florida, U.S.A.

The breeding success and chronology of Wood Storks Mycteria americana were studied at eight colonies in northern and central Florida during 1981–1985. Mean ± s.d. clutch size for all colony‐years was 3.07 ± 0.56 (n = 2694 nests), with three‐egg clutches (72%) most frequent. Mean clutch size among all colonies and years ranged from 2.73 ± 0.55 to 3.41 ± 0.61. Many colonies exhibited significant negative trends in clutch size with, hatching date because of a proportional decrease in four‐egg clutches later in the season. Mean colony clutch size was not correlated with nest numbers, nesting density or mean hatching date within most years. Mean ± s.d. number of fledglings for all colonies and years was 1.29 ± 1.16 fledglings per nest (n = 2812 nests). Mean annual fledging rates in colonies ranged from 0 (colony failed) to 2.66 fledglings per nest. Most breeding failure occurred prior to egg hatching, and the second highest mortality occurred between hatching and 2 weeks of age. Four‐egg clutches fledged more storks than three‐egg clutches, which in turn were more successful than two‐egg clutches. However, all clutch sizes showed similar fledgling per egg rates. The seasonal decline in productivity was associated proportionally with smaller clutch sizes later in the breeding season. An increase in mean hatching date was correlated with an increase in latitude. There was greater within‐year breeding synchrony among colonies than interyear breeding synchrony within each colony. Breeding synchrony was not correlated with mean hatching date, latitude, longitude, nest numbers or nesting density.

Modeling effects of chemicals on a population: application to a wading bird nesting colony

An approach for the study of effects of chemical contamination of an avian population is described. The protocol consists of four components: (1) an individual model that is coupled with (2) a chemical exposure model; and (3) a population model together with (4) an effects model. The model-based protocol is generic, delineates types of information required for ecological assessment and lays the framework for the implementation of toxic effects in an individual-oriented model. The protocol is illustrated by modifying an existing individual-oriented model of a wood stork colony to incorporate sublethal and lethal effects of mercury contamination. Because of the paucity of available data on effects of chemicals on wading birds, information from experiments on other avian species is, by necessity, frequently extrapolated to dose-response formulations for wading birds; consequently, the results are qualitative in character and portray relationships determined to exist between certain species of birds and the toxic effects of mercury pollution. Simulation results and applications focus on a population level effect, colony survival of the endangered species Mycteria americana in the Everglades of Florida. Because of the lack of information about model processes and parameter values for mercury effects on wood storks, model sensitivity studies were performed. Given the results for sublethal contamination levels along with the information on levels of mercury found in fish of the Everglades, it would seem that if our assumptions are even close to accurate, this model suggests that wood stork colony losses due to mercury contamination are feasible, possibly in the short term, but definitely in the long term.