Thomas M. Murphy

ESTABLISHING A FOOD-CHAIN LINK BETWEEN AQUATIC PLANT MATERIAL AND AVIAN VACUOLAR MYELINOPATHY IN MALLARDS (ANAS PLATYRHYNCHOS)

Avian vacuolar myelinopathy (AVM) is a neurologic disease primarily affecting bald eagles (Haliaeetus leucocephalus) and American coots (Fulica americana). The disease was first characterized in bald eagles in Arkansas in 1994 and then in American coots in 1996. To date, AVM has been confirmed in six additional avian species. Attempts to identify the etiology of AVM have been unsuccessful to date. The objective of this study was to evaluate dermal and oral routes of exposure of birds to hydrilla (Hydrilla verticillata) and associated materials to evaluate their ability to induce AVM. Mallards (Anas platyrhynchos) were used in all trials; bobwhite quail (Colinus virginianus) also were used in one fresh hydrilla material exposure trial. Five trials were conducted, including two fresh hydrilla material exposure trials, two cyanobacteria exposure trials, and a frozen hydrilla material exposure trial. The cyanobacteria exposure trials and frozen hydrilla material trial involved gavaging mallards with either Pseudanabaena catenata (live culture), Hapalosiphon fontinalis, or frozen hydrilla material with both cyanobacteria species present. With the exception of one fresh hydrilla exposure trial, results were negative or inconclusive. In the 2002 hydrilla material exposure trial, six of nine treated ducks had histologic lesions of AVM. This established the first cause-effect link between aquatic vegetation and AVM and provided evidence supporting an aquatic source for the causal agent.

MERCURY IN BALD EAGLE NESTLINGS FROM SOUTH CAROLINA, USA

Bald eagles (Haliaeetus leucocephalus) may be at risk from contaminants in their diet and young birds may be particularly sensitive to contaminant exposure. To evaluate potential risks from dietary mercury exposure to eagle nestlings in South Carolina (USA), we surveyed mercury concentrations in 34 nestlings over two breeding seasons (1998 and 1999). Samples were also obtained from several post-fledging eagles in the region. Nestling feather mercury ranged from 0.61–6.67 μg Hg/g dry weight, nestling down mercury from 0.50–5.05 μg Hg/g dry weight, and nestling blood mercury from 0.02–0.25 μg Hg/g wet weight. We did not detect significant differences in tissue mercury between nestlings from coastal and inland regions in contrast to some other studies of piscivorous birds. Mercury concentrations were much higher in the post fledging birds we sampled. Our data show that nestling eagles in South Carolina are accumulating mercury, and that concentrations in older birds may exceed regulatory guidelines.

THE PARASITE FAUNA OF THE AMERICAN ALLIGATOR (Alligator mississippiensis) IN SOUTH CAROLINA1

Twelve American alligators (Alligator mississippiensis) were obtained from three different areas of South Carolina. One species of pentastome (Sebekia oxycephala), two species of nematodes (Dujardinascaris waltoni and Multicaecum tenuicolle), four species of trematodes (Polycotyle ornata, Acanthostomum coronarium, Archaeodiplostomum acetabulatum and Pseudocrocodilicola americaniense) and one species of hemogregarine (Haemogregarina crocodilnorum) were recovered. Polycotyle ornata was observed only in alligators from Par Pond while P. americaniense was found in Par Pond and coastal hosts, A. acetabulatum from Kiawah Island and coastal alligators, and A. coronarium only at Kiawah Island. These patterns suggest disjunct distributions for the trematode species in South Carolina alligators. The other parasites were found in alligators from all three locations. The only parasite observed to initiate damage or lesions in the alligator was the pentastome.

INVESTIGATION OF THE LINK BETWEEN AVIAN VACUOLAR MYELINOPATHY AND A NOVEL SPECIES OF CYANOBACTERIA THROUGH LABORATORY FEEDING TRIALS

Avian vacuolar myelinopathy (AVM) is a neurologic disease affecting Bald Eagles (Haliaeetus leucocephalus), American Coots (Fulica americana), and other birds in the southeastern United States. The cause of the disease has not yet been determined, although it is generally thought to be a natural toxin. Previous studies have linked AVM to aquatic vegetation, and the current working hypothesis is that a species of cyanobacteria growing epiphytically on that vegetation is producing a toxin that causes AVM. Surveys of epiphytic communities have identified a novel species of cyanobacteria in the order Stigonematales as the most likely suspect. The purpose of this study was to further examine the relationship between the suspect Stigonematales species and induction of AVM, by using animal feeding trials. Adult Mallards and domestic chickens were fed aquatic vegetation from two study sites containing the suspect cyanobacterial epiphyte, as well as a control site that did not contain the Stigonematales species. Two trials were conducted. The first trial used vegetation collected during mid-October 2003, and the second trial used vegetation collected during November and December 2003. Neither treatment nor control birds in the first trial developed AVM lesions. Ten of 12 treatment Mallards in the second trial were diagnosed with AVM, and control birds were not affected. This study provides further evidence that the novel Stigonematales species may be involved with AVM induction, or at the least it is a good predictor of AVM toxin presence in a system. The results also demonstrate the seasonal nature of AVM events.

Accuracy and precision of techniques for counting great blue heron nests

Managing colonially nesting wading bird populations is often hampered by the lack of reliable information on colony sizes and population status. Therefore, we evaluated 9 techniques for accuracy and precision of counting great blue heron (Ardea herodias) nests in South Carolina. We examined accuracy by comparing percent deviation of technique estimates from corresponding ground counts. Precision of the different techniques was evaluated by comparing 95% confidence intervals for predicting individual colony size and the statewide nesting population. Techniques included point count, perimeter count, 40% sampling with 4-m-wide transects, 20% sampling with 2- and 4-m-wide transects, aerial estimate, aerial count, aerial photographic count, and post-nesting ground count. Error rates varied among techniques and for colonies containing 320 nests) colonies, post-nesting ground counts, aerial estimates, and all transect techniques had acceptable confidence interval widths ( 20%). Although couting techniques were not precise enough to be used for an estimate of the statewide nesting effort, managers using a combination of aerial counts of small (<50 nests) colonies and ground counts of other colonies should be able to detect a 15% change in nesting between years.

Breeding Season Abundance and Distribution of American Oystercatchers in South Carolina

Abstract Three statewide surveys in South Carolina for American Oystercatchers, Haematopus palliatus, were conducted during the breeding season from 2001-2003. A mean of 1,105 oystercatchers were recorded each year. In 2002, 407 breeding pairs were documented and in 2003, 397 pairs. There were 378 nonbreeding oystercatchers in 2002 and 383 in 2003. The Cape Romain Region supported a majority of South Carolina’s breeding pairs and nonbreeding flocks. Oystercatchers nested, on average, closer to each other on estuarine islands, (specifically made of shell) and farthest apart on edge shell mounds. Although historically oystercatchers may have nested primarily on front beaches, this study documented only 28% of the breeding pairs on barrier island beaches, 27% on estuarine islands and 45% on edge shell mounds. Twenty-four percent of all pairs in South Carolina were on edge shell mounds adjacent to the Atlantic Intracoastal Waterway (AIWW). Nesting on shell mounds may become increasingly important as beaches become more disturbed by humans and dogs.

Recent Occurrence, Spatial Distribution, and Temporal Variability of Leatherback Turtles (Dermochelys coriacea) in Nearshore Waters of South Carolina, USA

ABSTRACT Based on museum and stranding records, leatherback turtles (Dermochelys coriacea) were previously considered a rare migrant in South Carolina nearshore waters with only 9 recorded prior to 1980. In 1989, leatherback sightings increased, both alive and dead, in large numbers. From 1980 to 2003, 141 leatherback carcasses stranded. These leatherback strandings were highly seasonal, with a major peak in spring and a minor peak in fall. Based on 23 necropsies, there were 7 males and 16 females (1:2.3). From 1994 to 2003, during April–June, 1131 live leatherbacks (0.04 per km) were observed during 50 nearshore aerial surveys flown parallel to the South Carolina coast. The highest concentration during a single flight was in May 2002, with 175 leatherbacks seen over 605 km of transect line or 0.29 per km. Leatherbacks were not randomly or uniformly distributed, but had a contagious (clumped) distribution. Numbers observed varied significantly between inner and outer transect lines, among years, and among flights within a year. These lines of evidence demonstrate the recent occurrence, spatial distribution, and temporal variability of leatherbacks in South Carolina nearshore waters.

A Twenty-Six Year History of Wood Stork Nesting in South Carolina i1524-4695-31-sp1-3-

Abstract Since the first documented successful nesting of Wood Storks (Mycteria americana) in South Carolina in 1981, a total of 16,642 nesting attempts have been recorded. During the past 26 years, annual nesting has increased from eleven to a high of 2,057 nests in 2004. Storks have used 27 different colony sites, however, five sites have supported 76.3% of all nesting attempts. Mean colony size was 118 nests (range 1-547). Colony turnover rate was 0.19 overall based on annual calculations. However, 95.6% of colonies with more than 100 nests in one year were active the following year (N = 68). Only three of 27 sites are in public ownership and 21 sites are in wetlands altered or maintained by man. Production of young has been high each year (x bar = 2.08 young per successful nest) and abandonment of active colonies has been rare. This may result from the availability of varied habitats used by foraging storks. Nesting storks use palustrine habitats associated with rivers, inter-tidal wetlands, isolated wetlands and marsh impoundments. The variety of habitats used, combined with the topography of our coastal plain, provide adequate foraging habitat under a wide range of rainfall conditions.