Mycteria Americana Research Articles

Nesting Sites and Population Estimates of Seabirds and other Waterbirds of the Gulf of Chiriquí, Panamá

Abstract.— Little information exists on nesting by seabirds and coastal waterbirds in Panama. The present study of the Gulf of Chiriqui complements our previous study of nesting waterbirds of the Gulf of Panama. In April 2012, about 4,000 nests of seven species of seabirds and other colonial waterbirds were identified during a complete survey by small plane and boat within and adjacent to the Gulf of Chiriqui. Seventeen colony sites were found, 12 of which are reported here for the first time. Nesting species included Brown Booby (Sula leucogaster; the most abundant species with nearly 2,500 nests), Brown Pelican (Pelecanus occidentalis), Magnificent Frigatebird (Fregata magnificens), Bridled Tern (Onychoprion anaethetus; second nesting site for Panama), Wood Stork (Mycteria americana; third nesting site for Panama), Great Egret (Ardea alba), and Cattle Egret (Bubulcus ibis). The largest nesting site in the Gulf of Chiriqui was the Islas Ladrones, with 2,200 Brown Booby nests (the largest site for this sp...

Precipitation influences on uptake of a global pollutant by a coastal avian species

Climatic variation, including precipitation amounts and timing, has been linked to abundance and breeding success of many avian species. Less studied, but also of significance, is the consequence of climatic variability on the exposure and uptake of nutrients and contaminants by wildlife. The authors examined mercury (Hg) concentrations in nestling wood stork feathers in a coastal setting over a 16-yr period to understand the influence of rainfall amounts on Hg transfer by parental provisioning relative to habitat use, assuming differential bioavailability of Hg within freshwater and saltwater habitat types. Coastal Hg uptake by stork nestlings was linked to freshwater habitat use, as indicated by stable carbon isotope (δ(13)C) analyses. Cumulative rainfall amounts exceeding 220 cm in the 23 mo preceding the breeding seasons resulted in greater use of freshwater wetlands as foraging habitat and greater Hg accumulation by nestling storks.

Movements and Habitat Use by Fledgling Wood Storks(Mycteria Americana)Prior to Dispersal from the Natal Colony

Abstract.Activity patterns of fledgling storks (Ciconiidae) during the parental-dependency period are poorly understood for many species, including the Wood Stork (Mycteria americana). Satellite telemetry was used to track the movements of fledgling Wood Storks ( n = 50) from the time they attained minimum flight capabilities until dispersal from the natal colony. Distances traveled, range size, and habitat use by fledgling Wood Storks were quantified for early (prior to the final week before dispersal) and late (the final week before dispersal) predispersal periods and for the entire predis-persal period as a whole. Metrics were compared among three colonies and between two years at a single colony using nonparametric tests. For the entire predispersal period, the mean daily maximum distance of juvenile Wood Storks from their nest was 1.39 ± 0.2 km (median = 0.18 and maximum = 103.13) and the mean cumulative distance moved per day was 2.38 ± 0.28 km (median = 0.45 and maximum = 110.58). Movement distance...

Characterization of Tidally Influenced Wood Stork Foraging Habitats in Georgia

To characterize tidally influenced Wood Stork foraging habitats, we documented the physical structure and potential prey populations of 17 known (based primarily on satellite telemetry locations) foraging and 20 “alternate” (similar habitat) sites, tidal creeks, in coastal Georgia. The majority of sites contained reaches partially impounded by three landscape features: oyster-shell dams, root/mud dams, or the junction of two or more creeks. Potential prey species, dominated by Fundulus heteroclitus (Mummichog) and shrimp, were highly variable among the tidal habitats but generally occurred in densities (average > 140 individuals/m2) far greater than those observed in an earlier inland Georgia study. There were no differences in potential prey densities between known foraging and alternate sites, confirming that the large salt marsh region of Georgia provides excellent foraging habitat for the regional Wood Stork population.

Wood Storks (Mycteria americana) Prey on Eggs and Hatchlings of Olive Ridley Sea Turtles (Lepidochelys olivacea) at Ostional, Costa Rica

Abstract. The foraging behavior of Wood Storks (Mycteria americana) has been studied extensively because of their dramatic population decline and endangered status. The foraging by Wood Storks at an arribada beach with olive ridley sea turtles (Lepidochelys olivacea; turtle) at Ostional, Costa Rica, was examined to determine their depredation behavior on turtle eggs and hatchlings. Wood Storks, in association with Black Vultures (Coragyps atratus), foraged on turtle nests exposed by stream, tidal, and wind erosion, and on nests dug up by dogs (Canis familiaris). Wood Storks also foraged on emerging turtle hatchlings and those crawling to the sea. Wood Storks concentrated near stream beds where nearly half of the predation events (eggs/hatchlings being eaten) occurred. Usually, one to three Wood Storks fed at a turtle nest; an average of 87% of the Wood Storks that were within 5 m of a turtle nest obtained eggs or hatchlings. The number of Wood Storks present and feeding, and the percent feeding, depended ...

Blood Parasites in Nestlings of Wood Stork Populations from Three Regions of the American Continent

This study documents the prevalences and lineages of hemoparasites in wood stork nestlings from 3 regions of the American continent: southeastern United States (n = 90), northern Brazil (n = 74), and central-western Brazil (n = 125). Identification was based on PCR amplification of a mitochondrial small subunit ribosomal RNA gene. A fragment of the hemoparasite cytochrome B gene in infected individuals was utilized for Bayesian phylogenetic analysis. Four wood stork nestlings were infected by Haemoproteus, 1 from northern Brazil and 3 from the United States, and all shared the same haplotype. Morphological analysis confirmed the infection of the U.S. birds by Haemoproteus. Infection by Plasmodium was found in wood stork nestlings from northern (6) and central-western Brazil (14). Five Plasmodium lineages (MYCAMP1-2, and MYCAMP4-6) were found in the Brazilian central-western region and 3 Plasmodium lineages (MYCAMP2-3, and MYCAMP7) were found in the northern region. The most prevalent haplotype (MYCAMP2) differs from the others by 1 mutation, and the less prevalent haplotypes are derived from MYCAMP2. We did not find Plasmodium or Haemoproteus in nestlings younger than 15 and 30 days old, respectively. This is the first documentation of Plasmodium and Haemoproteus infection in wood storks in Brazilian breeding populations. Potential connectivity among wood stork populations was indirectly supported by the presence of identical Haemoproteus lineages in U.S. and northern Brazilian populations, and by the presence of identical Plasmodium haplotypes in the northern and central-western Brazilian populations.

Productivity and Habitat Modeling of Wood Storks Nesting in North and Central Florida

Abstract Rainfall, surface water levels, location within the state, and area and types of habitats (n = 29) surrounding wood stork Mycteria americana colonies in North and Central Florida were analyzed at 10-km, 20-km, and 30-km radii around each colony to examine their relationship with fledging rate and number of nests during 2003–2005. Seven variables within 10 km, 14 variables within 20 km, and 6 variables within 30 km of colonies were correlated with fledging rates. Fledging rate and number of nests were significantly associated with both wetland and nonwetland area and habitats. Among all the variables, fledging rate was most strongly associated with rainfall during the preceding 12–24 mo. Both larger colonies and colonies in North Florida had higher fledging rates. Although some variables had a positive association and other variables had a negative correlation with fledging rates, results were not consistent across all three radii, which suggests that the effects of hydrologic and habitat variables differs with increasing distance from a colony. The size of a wood stork colony was sensitive to a larger number of variables and varied by distances from the colony. Colonies were smaller in the northern part of Florida, and coastal colonies were larger than interior colonies. Because wood storks often use ephemeral foraging sites closer to a colony early in the season and those sites may not be available later in the season, wood storks may shift to alternate, more distant sites and habitats later in the season. A hypothesis is proposed whereby wood storks establish their colonies using proximate clues of prey availability based on the effects of past rainfall and certain preferred habitat types. These proximate cues to prey availability and foraging substrate surrounding a colony are detected by wood storks before the onset and during the initial nesting season. However, the long-term stability of a colony may ultimately be determined by yearly rainfall patterns and habitat variables at larger distances and by fledging rates that contribute to recruitment of nesting birds and an increase in number of nests.

Temporal variation in local wetland hydrology influences postdispersal survival of juvenile Wood Storks (Mycteria americana)

Since the 1960s, anthropogenic shifts in the timing and distribution of surface-water flows in the Everglades have pushed back the onset of reproduction in Wood Storks (Mycteria americana). Late nesting increases the probability that juveniles leave the colony during the summer rainy season, when water levels are high and prey animals unavailable. We used satellite telemetry to track firstyear survival of 85 Wood Storks from southern Florida over 4 years. We further evaluated survival in relation to hydrologic and physiologic variables, including water depths, surface-water recession rates, May rainfall, use of wetland habitats, sex, total feather mercury, whiteblood-cell counts, and heterophih:lymphocyte ratios for a subset of 71 birds, using a known-fates model in Program MARK. Juveniles that dispersed from the colony during favorable conditions (surface water depths <25 cm) had a first-year survival rate of 0.37 ± 0.06 (SE), compared with 0.15 ± 0.04 for those that dispersed into unfavorable conditions (depths >25 cm). General hydrologie conditions (favorable vs. unfavorable), wetland habitat use, and white-blood-cell counts were the best predictors of monthly survival, and the strongest effects were associated with the first month postdispersal. Our study is the first to show a relationship between temporally fluctuating hydrologic variables and survival of juvenile Wood Storks, highlighting the need to consider the timing of hydrologic manipulations when managing wetlands for birds. We conclude that human-induced changes in the temporal patterns of hydrology may have important consequences for the phenology and, ultimately, the demography of wetland birds.

Adapting foraging to habitat heterogeneity and climate change: an individual-based model for wading birds

In an effort to assess the role of adaptive foraging behaviour to the spatial and temporal heterogeneity as a factor determining the success of the colony, we used single-colony individual-based spatial models for a visual foraging, the Great Blue Heron and a tactile foraging bird, the Wood Stork. The model followed simultaneously daily activities of individuals, their spatial movements, foraging efficiency, bioenergetics and growth of the nestlings during a nesting season. For each colony we used two scenarios; in the first, that depicted a normal nesting season, the extent and distribution of feeding sites led to successful reproduction for both species. In the second, we simulated increased precipitation regimes resulting in reversals in water depth (i.e. increases in depth during the dry season when water levels are normally falling). The results reveal that Wood Storks were significantly more adversely affected than Great Blue Herons by the prey dilution caused by the reversals in water depth. In the latter scenario where resources became scarce, resource predictability decreased. The foraging birds that foraged in groups exhibited low foraging success, resulting in poor reproductive performance. This result was more pronounced in the case of storks that foraged in groups than for herons foraging in groups. Concluding, increased variance in precipitation regimes is more likely to affect tactile rather than visual foraging bird species. Further, in harsh climatic conditions (increased precipitation and water level regimes) solitary foraging was more beneficial for wading birds than group foraging.

Foraging Habitat use by Breeding Wood Storks and the Core Foraging Area Concept

Abstract. Wood Stork (Mycteria americana) foraging flight studies at 20+ colonies throughout the US range were reviewed to summarize foraging ranges and compared to 20, 25 and 30 km-wide regulatory buffers (“core foraging areas”) created to provide sufficient foraging habitats for breeding storks. Mean (per colony) direct distances to foraging sites ranged from 2.7 to 18.1 km, and between 75-100% of all follow flights went to foraging sites within 20 km of their colony. Overall, reviewed follow flight data suggested that the 20-km buffer would be sufficient for all breeding colonies in the US. However, such a reduction is not supported at this time due to limited recent data for certain regions of the Wood Stork breeding range (e.g. central and southern Florida). Additional, preferably multi-year, foraging habitat use studies are needed to fill data gaps for these areas to better assess the validity of the CFA buffers.

Sedentary nestlings of Wood Stork as monitors of mercury contamination in the gold mining region of the Brazilian Pantanal

Sedentary organisms that are at top trophic levels allow inference about the level of local mercury contamination. We evaluated mercury contamination in feather tissue of nestling Wood Storks (Mycteria americana), sampled in different parts of the Brazilian Pantanal that were variably polluted by mercury releases from gold mining activities. Levels of mercury in feathers sampled in seven breeding colonies were determined by atomic absorption spectroscopy, and the mean value of mercury concentration was 0.557μg/g, dry weight (n=124), range 0.024–4.423μg/g. From this total sample, 21 feathers that represent 30% of nestlings collected in Porto da Fazenda and Tucum colonies, in the northern region, ranged from 1.0 to 4.43μg/g, dry weight (median value=1.87μg/g). We found significant differences among regions (H=57.342; p=0<0.05). Results suggest that permanently flooded areas, or along mainstream rivers are more contaminated by mercury than dry areas, regardless of the distance from the gold mining center, which is located in the northern Pantanal. Highest values found in nestlings feathers were similar to those found in feathers of adult birds and in tissues of adult mammals that are less sedentary and were captured in the same region of Pantanal. These findings indicate that mercury released has been biomagnified and it is present in high concentrations in tissues of top consumers. We suggest a program to monitor mercury availability in this ecosystem using sedentary life forms of top predators like Wood Storks or other piscivorous birds.

Reconstructing genetic mating systems in the absence of parental information in colonially breeding waterbirds

BackgroundDNA-based studies have demonstrated that avian genetic mating systems vary widely, with many species deviating from long-assumed monogamy by practicing extra-pair paternity and conspecific brood parasitism. Colonially breeding waterbirds provide interesting models in which to investigate this question because they show nesting habits proposed to promote alternative reproductive strategies. However, little is known about the genetic mating systems of this group of birds, mainly due to difficulties in obtaining genetic data from incubating adults at nests that are necessary for conducting conventional parentage studies. Here, we inferred kinship patterns among offspring in broods of three co-distributed waterbird species, Wood Stork (Mycteria americana), Roseate Spoonbill (Platalea ajaja) and Great Egret (Ardea alba egretta), to investigate genetic mating system in the absence of parental data.ResultsMulti-step analyses combining estimates of relatedness coefficients, formulation of relationship-hypotheses, significance testing of alternative hypotheses, and maximum-likelihood sibship reconstruction techniques revealed evidence that alternative reproductive strategies may be present in natural populations of Wood Storks and Roseate Spoonbills, whereas relatedness of co-nestlings diagnosed in the Great Egrets did not deviate from a hypothesis of genetic monogamy. Specifically, under this analytical framework, inferred kinship relationships revealed that Great Egret nests contained full-sibling nestlings (100%), with the Roseate Spoonbill (RS) and Wood Stork (WS) exhibiting proportions of half-siblings (RS: 5%) and/or unrelated nestlings (RS: 24%; WS: 70%), patterns consistent with extra-pair paternity and conspecific brood parasitism, respectively.ConclusionsWe provide evidence that genetic monogamy occurs in Brazilian natural breeding colonies of the Great Egret, but is not the sole reproductive strategy employed by the Wood Stork and the Roseate Spoonbill. In fact, extra-pair paternity and conspecific brood parasitism were common in the latter two species, with a combined frequency of 7.5% and 11.3% in Roseate Spoonbill and Wood Stork, respectively. Although geographically co-distributed, differences among these species may be due to variation in their life histories. From a methodological standpoint, the approach implemented here, although not free from limitations, can have broad application for analyzing systems with limited genealogical information and/or in studying similarly challenging organisms in which obtaining genetic data on complete families is problematic.

Resource Selection Functions for Wood Stork Foraging Habitat in the Southern Everglades

Modeling habitat selection of species with specific foraging requirements is an effective means to evaluate landscape quality for restoration and conservation purposes. Proportional hazards regression, a discrete choice model, was used to develop resource selection functions for breeding Wood Stork in the southern Everglades during the 2006 nesting season. Wood Storks showed the highest probability of habitat selection in a narrow range of shallow water depths. The quadratic form of water depth (depth depth2) was an important indicator of habitat selection with mean water depths between -25 and 25 cm receiving the highest probability of use (a negative water depth is below average ground elevation). Foraging sites within 20 km of nesting colonies were selected over farther sites. Shrub swamp, mangrove swamp and saltwater marsh vegetation types were used in higher proportions than they occurred in the landscape. Results exemplify the importance of shallow water depths near established stork breeding colonies throughout the breeding season.

Quantitative analysis of foraging habitat use by ciconiiformes in the upper Paraná river Floodplain, Brazil

The aim of this study was to analyze the seasonal variations in habitat selection and abundance of Ciconiiformes species in four foraging habitats (rivers, channels, connected and disconnected lagoons) on the upper Parana River floodplain, Brazil, and to conduct the surveys of wading birds in 2002 and 2003. The largest number of species and highest abundances of most species were observed in the connected lagoons. Snowy Egrets (Egretta thula), Wood Storks (Mycteria americana), Roseate Spoonbills (Platalea ajaja), and Jabirus (Jabiru mycteria) frequently used connected lagoons (habitat with the highest fish abundance) and abandoned the areas during floods, suggesting that they were able to find high quality patches for foraging. Cocoi Herons (Ardea cocoi), Great Egrets (Ardea alba), and Rufescent Tiger-Herons (Tigrisoma lineatum) used habitats with lower fish abundance and did not totally abandon these areas during floods, suggesting they were not dependent on high quality patches. Differences in foraging techniques and social behavior explained the difference between the two groups. The results showed that opportunism did not totally explain the foraging habitat selection and in low water level seasons there were higher differences in foraging behavior among the species.

Birds Consumed by the Invasive Burmese Python (Python molurus bivittatus) in Everglades National Park, Florida, USA

We identified 25 species of birds representing nine avian Orders from remains in digestive tracts of 85 Burmese pythons (Python molurus bivittatus) collected in Everglades National Park, Florida, USA, from 2003 to 2008. Four species of birds identified in this study are of special concern in Florida and a fifth, the Wood Stork (Mycteria americana), is listed as federally endangered. This represents the first detailed analysis of the avian component of the diet of the introduced Burmese python, now established in Everglades National Park, Florida and highlights the potential for considerable negative impact of this invasive species on native bird populations. Received 9 June 2010. Accepted 27 September 2010.

Genetic status of the wood stork (Mycteria americana) from the southeastern United States and the Brazilian Pantanal as revealed by mitochondrial DNA analysis

The wood stork (Mycteria americana) is a colonial wading bird that inhabits the Neotropical region from the southeastern United States (US) to northern Argentina. The species is considered to be endangered in the US due to degradation of its foraging and breeding habitat. In other parts of its range, such as in the Brazilian Pantanal region, breeding populations of this species appear to be stable. We compared the levels of genetic variability and population structuring of the US and the Pantanal breeding populations using mitochondrial DNA (mtDNA) control region sequences. Twenty-seven haplotypes were identified among 88 wood stork samples collected from eight breeding colonies in the US and eight in the Pantanal. Patterns indicative of heteroplasmy were observed in 35.3% of the mtDNA sequences that were examined. Significantly higher levels of haplotype diversity were observed in the Pantanal samples compared to those from the US, suggesting that during the last century, demographic declines or a recent evolutionary bottleneck reduced the levels of mtDNA variability of the US population. Analyses of genetic structuring revealed non-significant genetic differentiation between these regions, indicating that either the populations were only recently separated or that gene flow continues to occur at low levels. Haplotype network analysis indicated low current levels of gene flow between populations that were closely related in the past.

Isolation and characterization of a new suite of microsatellite markers in the European White Stork, Ciconia ciconia

The White Stork (Ciconia ciconia) has an extensive European breeding distribution. There have been significant demographic changes since the 1930s, with country-specific extinctions throughout the western distribution since the mid-1940s. Following various reintroduction programs significant concerns have been raised about the geographic origins of introduced storks, and the effect this may have on individual biology, particularly breeding success. Here we report on seven new microsatellite markers developed for C. ciconia that have been successfully combined in a series of multiplex PCR’s with six markers previously described for the Wood Stork.

The White Ibis and Wood Stork as indicators for restoration of the everglades ecosystem

Large numbers of colonially nesting herons, egrets, ibises, storks and spoonbills were one of the defining natural phenomena of the historical Everglades. Reproduction of these species has been tracked over at least a century, and some clear responses to dramatic anthropogenic hydrological alterations have been established. These include a marked decline in nesting populations of several species, and a movement of colonies away from the over-drained estuarine region. Ponding in a large portion of the freshwater marsh has favored species that hunt by sight in deep water (egrets, cf. 25–45 cm), while tactile feeders (ibises and storks) that depend on concentrated prey in shallow water (5–25 cm) have become proportionately much less common. There has been a marked increase in the interval between exceptionally large breeding aggregations of White Ibises (Eudocimus albus). Loss of short hydroperiod wetlands on the margins of the Everglades have delayed nest initiations 1–2 months by Wood Storks (Mycteria americana) resulting in poor nesting success. These responses are consistent with mechanisms that involve foraging, and the availability and production of prey animals, and each of the relationships is highly dependent on hydrology. Here, we define a group of characteristics about wading bird dynamics (= indicators) that collectively track the specific ecological relationships that supported ibises and storks in the past. We suggest four metrics as indicators of restoration success: timing of nesting by storks, the ratio of nesting ibises + storks to Great Egrets, the proportion of all nests located in the estuarine/freshwater ecotone, and the interval between years with exceptionally large ibis nestings. Each of these metrics has historical (e.g., predrainage) data upon which to base expectations for restoration, and the metrics have little measurement error relative to the large annual variation in numbers of nests. In addition to the strong scientific basis for the use of these indicators, wading birds are also a powerful tool for public communication because they have strong aesthetic appeal, and their ecological relationships with water are intuitively understandable. In the interests of communicating with the public and decision-makers, we integrate these metrics into a single-page annual “traffic-light” report card for wading bird responses. Collectively, we believe these metrics offer an excellent chance of detecting restoration of the ecosystem functions that supported historical wading bird nesting patterns.

Blood Parasites in Wood Storks (Mycteria americana) From the Southeastern United States

Wood storks (Mycteria americana) are endangered throughout their breeding range in the United States. Because of this, researchers have had little opportunity to thoroughly examine the continental wood stork population for endoparasites. The blood protozoan Haemoproteus crumenium has been identified from several populations of wood storks in North America. However, there have been no reports of wood storks being infected with species of Plasmodium or Leucocytozoon. During 2003, 42 nestling wood storks were captured at sites in Georgia and 27 free-ranging wood storks were captured at postbreeding dispersal sites in Mississippi and Louisiana. Two thin blood smears were made from each bird, and they were examined for parasites. Haemoproteus crumenium was found in 5 wood storks (7.2%), whereas Leucocytozoon sp., Plasmodium sp., and microfilariae were not observed. Mean intensity of H. crumenium was 4.4 +/- 0.7 (SE) per 2,000 erythrocytes counted. All infected wood storks were subadult or adult and were from postbreeding dispersal sites in Mississippi.

Ecological risk of methylmercury in Everglades National Park, Florida, USA

Dramatic declines in mercury levels have been reported in Everglades biota in recent years. Yet, methylmercury (MeHg) hot spots remain. This paper summarizes a risk assessment of MeHg exposure to three piscivorous wildlife species (bald eagle, Haliaeetus leucocephalus; wood stork, Mycteria americana; and great egret, Ardea albus) foraging at a MeHg hot spot in northern Everglades National Park (ENP). Available data consisted of literature-derived life history parameters and tissue concentrations measured in 60 largemouth bass (Micropterus salmoides), 60 sunfish (Lepomis spp.), and three composite samples of mosquitofish (Gambusia holbrooki) collected from 2003 to 2005. To assess risk, daily MeHg intake was estimated using Monte Carlo methods and compared to literature-derived effects thresholds. The results indicated the likelihood was very high, ranging from 98-100% probability, that these birds would experience exposures above the acceptable dose when foraging in northern ENP. Moreover, the likelihood that these birds would experience exposures above the lowest-observed-adverse-effect level (LOAEL) ranged from a 14% probability for the wood stork to 56% probability for the eagle. Data from this study, along with the results from several other surveys suggest that biota in ENP currently contain the highest MeHg levels in South Florida and that these levels are similar to or greater than other known MeHg hot spots in the United States. Given these findings, this paper also outlines a strategic plan to obtain additional measured and modeled information to support risk-based management decisions in ENP.