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.

Clinging to the top: natal dispersal tracks climate gradient in a trailing-edge population of a migratory songbird.

PURPOSE: Trailing-edge populations at the low-latitude, receding edge of a shifting range face high extinction risk from climate change unless they are able to track optimal environmental conditions through dispersal. METHODS: We fit dispersal models to the locations of 3165 individually-marked black-throated blue warblers (Setophaga caerulescens) in the southern Appalachian Mountains in North Carolina, USA from 2002 to 2023. Black-throated blue warbler breeding abundance in this population has remained relatively stable at colder and wetter areas at higher elevations but has declined at warmer and drier areas at lower elevations. RESULTS: Median dispersal distance of young warblers was 917 m (range 23-3200 m), and dispersal tended to be directed away from warm and dry locations. In contrast, adults exhibited strong site fidelity between breeding seasons and rarely dispersed more than 100 m (range 10-1300 m). Consequently, adult dispersal kernels were much more compact and symmetric than natal dispersal kernels, suggesting adult dispersal is unlikely a driving force of declines in this population. CONCLUSION: Our findings suggest that directional natal dispersal may mitigate fitness costs for trailing-edge populations by allowing individuals to track changing climate and avoid warming conditions at warm-edge range boundaries.

A single Haemoproteus plataleae haplotype is widespread in white ibis (Eudocimus albus) from urban and rural sites in southern Florida.

The American white ibis (Eudocimus albus), a common bird species in Florida, has become increasingly urban, with many populations relying heavily on urban and suburban habitats, which may alter parasite transmission. Parasites of ibis, especially haemosporidians, are understudied. Avian haemosporidia can have a wide range of impacts on birds, including decreased reproductive success or increased mortality. Because southern Florida is subtropical and has a high diversity of potential vectors for haemosporidia, we hypothesized that there will be a high prevalence and genetic diversity of haemosporidia in white ibis. A total of 636 ibis from South Florida were sampled from 2010 to 2022, and blood samples were tested for haemosporidia by examination of Giemsa-stained thin blood smears and/or nested PCRs targeting the cytochrome b gene. A total of 400 (62.9%, 95% CI 59-66.7%) ibis were positive for parasites that were morphologically identified as Haemoproteus plataleae. Sequences of 302 positives revealed a single haplotype of Haemoproteus (EUDRUB01), which was previously reported from white ibis in South Florida and captive scarlet ibis (E. ruber) in Brazil. No Plasmodium or Leucocytozoon infections were detected. Parasitemias of the 400 positive birds were very low (average 0.084%, range 0.001%-2.16% [although only 2 birds had parasitemias >1%]). Prevalence and parasitemias were similar for males and females (68% vs. 61.6% and 0.081% vs. 0.071%, respectively). Prevalence in juveniles was lower compared with adults (52% vs. 67.4%) but parasitemias were higher in juveniles (0.117% vs. 0.065%). This data shows that H. plataleae is common in ibis in South Florida. Although parasitemias were generally low, additional research is needed to determine if this parasite has subclinical effects on ibis, if additional haplotypes or parasite species infect ibis in other regions of their range, or if H. plataleae is pathogenic for other sympatric avian species.