HEMATOLOGY, BIOCHEMISTRY, AND METAL CONTAMINANT LEVELS IN WILD-CAUGHT CLAPPER RAIL (RALLUS CREPITANS) IN NORTHEASTERN FLORIDA.

The clapper rail (Rallus crepitans) is native to salt marshes along the eastern United States. Populations are likely stable, but may be at risk due to the degradation of wetland habitat by contaminants. Contaminants can cause adverse effects in birds such as alteration of immune and reproductive function, and previous studies have used this species as a sentinel for estuarine health. Blood samples were collected from clapper rails in Florida and hematology counts, plasma biochemistry panels, and metal assessments using inductively coupled plasma-mass spectrometry were performed. Biochemical and hematology data were too limited to determine if contaminants were adversely affecting clapper rails in this study, but cadmium, lead, and zinc were increased for several birds. Although contaminant levels were not consistently elevated for all birds, additional research is needed to assess if clapper rails in this region are at risk of contaminant exposure due to increasing urbanization and development pressures.

Levels of Mercury in Feathers of Clapper Rails (Rallus crepitans) over 45 Years in Coastal Salt Marshes of New Hanover County, North Carolina.

We sampled clapper rail (Rallus crepitans) feathers from museum specimens collected between 1965 and 2010 to investigate changes in mercury (Hg) availability in coastal marshes of New Hanover County, North Carolina. Stable isotope analysis (δ(13)C and δ(15)N) was conducted to control for dietary shifts that may have influenced Hg exposure. Hg concentrations ranged from 0.96 to 9.22 µg/g (ppm), but showed no significant trend over time; diet (δ(15)N) or foraging habitat (δ(13)C) also provided little to no explanatory power to the variation in Hg concentrations among clapper rails. Our findings suggest the bioavailability of Hg to clapper rails in coastal North Carolina salt marshes has remained consistent over time, despite the global trend of increasing mercury in many other bird species, providing an excellent baseline for any future assessment of Hg availability to salt marsh birds in coastal North Carolina.

Availability and assessment of microplastic ingestion by marsh birds in Mississippi Gulf Coast tidal marshes.

Millions of tons of plastic enter the environment every year, where much of it concentrates in environmental sinks such as tidal marshes. With prior studies documenting harm to marine fauna caused by this plastic pollution, the need to understand how this novel type of pollution affects estuarine fauna is great. Yet, research on the fate and uptake of plastic pollutants in estuarine ecosystems is sparse. Therefore, we quantified plastic prevalence and ingestion by two species of resident marsh bird, Clapper Rails (Rallus crepitans) and Seaside Sparrows (Ammospiza maritima), in coastal marsh ecosystems within Mississippi. We detected microplastics (plastics smaller than 5 mm) in 64% of marsh sediment samples, 83% of Clapper Rail and 69% of Seaside Sparrow proventriculus samples. Dominant types of microplastics detected in sediment and bird samples were fibers. This study provides the first evidence of microplastic ingestion by marsh birds and its distribution in coastal marshes within Mississippi.

Genetic analyses reveal cryptic introgression in secretive marsh bird populations.

Hybridization is common in bird populations but can be challenging for management, especially if one of the two parent species is of greater conservation concern than the other. King rails (Rallus elegans) and clapper rails (R. crepitans) are two marsh bird species with similar morphologies, behaviors, and overlapping distributions. The two species are found along a salinity gradient with the king rail in freshwater marshes and the clapper in estuarine marshes. However, this separation is not absolute; they are occasionally sympatric, and there are reports of interbreeding. In Virginia, USA, both king and clapper rails are identified by the state as Species of Greater Conservation Need, although clappers are thought to be more abundant and king rails have a higher priority ranking. We used a mitochondrial DNA marker and 13 diagnostic nuclear single nucleotide polymorphisms (SNPs) to identify species, classify the degree of introgression, and explore the evolutionary history of introgression in two putative clapper rail focal populations along a salinity gradient in coastal Virginia. Genetic analyses revealed cryptic introgression with site-specific rates of admixture. We identified a pattern of introgression where clapper rail alleles predominate in brackish marshes. These results suggest clapper rails may be displacing king rails in Virginia coastal waterways, most likely as a result of ecological selection. As introgression can result in various outcomes from outbreeding depression to local adaptation, continued monitoring of these populations would allow further exploration of hybrid fitness and inform conservation management.