Composition and Drivers of Gut Microbial Communities in Arctic-Breeding Shorebirds.

Gut microbiota can have important effects on host health, but explanatory factors and pathways that determine gut microbial composition can differ among host lineages. In mammals, host phylogeny is one of the main drivers of gut microbiota, a result of vertical transfer of microbiota during birth. In birds, it is less clear what the drivers might be, but both phylogeny and environmental factors may play a role. We investigated host and environmental factors that underlie variation in gut microbiota composition in eight species of migratory shorebirds. We characterized bacterial communities from 375 fecal samples collected from adults of eight shorebird species captured at a network of nine breeding sites in the Arctic and sub-Arctic ecoregions of North America, by sequencing the V4 region of the bacterial 16S ribosomal RNA gene. Firmicutes (55.4%), Proteobacteria (13.8%), Fusobacteria (10.2%), and Bacteroidetes (8.1%) dominated the gut microbiota of adult shorebirds. Breeding location was the main driver of variation in gut microbiota of breeding shorebirds (R 2 = 11.6%), followed by shorebird host species (R 2 = 1.8%), and sampling year (R 2 = 0.9%), but most variation remained unexplained. Site variation resulted from differences in the core bacterial taxa, whereas rare, low-abundance bacteria drove host species variation. Our study is the first to highlight a greater importance of local environment than phylogeny as a driver of gut microbiota composition in wild, migratory birds under natural conditions.

Phenological mismatch in Arctic-breeding shorebirds: Impact of snowmelt and unpredictable weather conditions on food availability and chick growth.

The ecological consequences of climate change have been recognized in numerous species, with perhaps phenology being the most well-documented change. Phenological changes may have negative consequences when organisms within different trophic levels respond to environmental changes at different rates, potentially leading to phenological mismatches between predators and their prey. This may be especially apparent in the Arctic, which has been affected more by climate change than other regions, resulting in earlier, warmer, and longer summers. During a 7-year study near Utqiagvik (formerly Barrow), Alaska, we estimated phenological mismatch in relation to food availability and chick growth in a community of Arctic-breeding shorebirds experiencing advancement of environmental conditions (i.e., snowmelt). Our results indicate that Arctic-breeding shorebirds have experienced increased phenological mismatch with earlier snowmelt conditions. However, the degree of phenological mismatch was not a good predictor of food availability, as weather conditions after snowmelt made invertebrate availability highly unpredictable. As a result, the food available to shorebird chicks that were 2-10 days old was highly variable among years (ranging from 6.2 to 28.8 mg trap-1 day-1 among years in eight species), and was often inadequate for average growth (only 20%-54% of Dunlin and Pectoral Sandpiper broods on average had adequate food across a 4-year period). Although weather conditions vary among years, shorebirds that nested earlier in relation to snowmelt generally had more food available during brood rearing, and thus, greater chick growth rates. Despite the strong selective pressure to nest early, advancement of nesting is likely limited by the amount of plasticity in the start and progression of migration. Therefore, long-term climatic changes resulting in earlier snowmelt have the potential to greatly affect shorebird populations, especially if shorebirds are unable to advance nest initiation sufficiently to keep pace with seasonal advancement of their invertebrate prey.

Nest box-deployed bait for delivering oral vaccines to white-footed mice.

Although a wide range of interventions are available for use in reducing the public health burden of Lyme disease, additional tools are needed. Vaccinating mouse reservoirs may reduce the prevalence of spirochetal infection due to the powerful vector and reservoir competence-modulating effects of anti-outer surface protein A (OspA) antibody. A delivery system for an oral immunogen would be required for field trials of any candidate vaccine. Accordingly, we tested candidate bait preparations that were designed to be environmentally stable, attractive to mice, and non-nutritive. In addition, we determined whether delivery of such baits within nest boxes could effectively target white-footed mice. A peanut butter-scented bait was preferred by mice over a blueberry-scented one. At a deployment rate of 12.5 nest boxes per hectare, more than half of resident mice ingested a rhodamine-containing bait, as demonstrated by fluorescent staining of their vibrissae. We conclude that a peanut butter-scented hardened bait placed within simple wood nest boxes would effectively deliver vaccine to white-footed mice, thereby providing baseline information critical for designing field trials of a candidate oral vaccine.

Prevalence of Ehrlichia muris in Wisconsin Deer Ticks Collected During the Mid 1990s.

Human ehrlichiosis is due to infection by tick transmitted bacteria of the genus Ehrlichia. Based on a hypothesis for the biogeography of deer tick transmitted infections, we undertook a focused search for the Eurasian E. muris in North American deer ticks. The search was stimulated by anecdotal reports of E. muris-like infection in human ehrlichiosis patients from Wisconsin. We analyzed archived adult deer ticks collected in northern Wisconsin during the 1990s by specific polymerase chain reaction for evidence of infection, and sequenced amplification products to identify E. muris. About 1% of 760 adult deer ticks collected from Spooner, Wisconsin in the 1990s contained E. muris DNA. We conclude that E. muris was present in North American deer ticks a decade ago and is likely to infect this human biting vector elsewhere in the U.S. Biogeographic theory and molecular phylogenetic methods can facilitate a targeted search for potential zoonoses.