Ornithology II

Contributed Oral

Effects of Blood Mercury Concentrations on the Prevalence of Avian Malaria in Central Louisiana
Maria Ferrer, Jared Wolfe, Kristin Brzeski, Collin Eagles-Smith, Allyson Jackson, Erik Johnson, Eric Tobin

Avian malaria (genus Plasmodium), a protozoan parasite transmitted by mosquito vectors, is prevalent across a wide variety of bird species. Additionally, heavy metal poisoning from persistent environmental pollutants such as Mercury and the bioavailable form, Methylmercury (CH3Hg), can cause immunosuppression and endocrine disruption thereby negatively affecting the avian immune system and bird health. As such, we hypothesize that birds exposed to elevated levels of Methylmercury will be immunocompromised resulting in higher prevalence of avian malaria. To test our hypothesis, we will focus on Carolina Wrens (Thryothorus ludovicianus), an insectivorous songbird that is commonly exposed to Methylmercury through its diet on predatory insects. Specifically, we will investigate the relationship between mercury blood concentrations and parasite prevalence found among Carolina Wrens captured in Louisiana. Thus far, we have assessed mercury exposure of 835 individual Carolina Wrens that were captured in Louisiana between 2012-2015. We will use blood from these same individuals to screen for presence/absence of avian malaria using a nested PCR analysis, by amplifying the cytochrome b gene of the parasites, and then sequence each positive infection for parasite lineage within the genus Plasmodium. We expect to find that mercury exposed birds will have a higher prevalence of avian malaria compared to birds that have lower levels of blood mercury. Our results will help integrate epidemiology into conservation planning by determining how persistent environmental pollution can interact with pathogens to affect bird health.

Demography and Destination: Modeling Summer Survival and Winter Migration of Canada Warblers in the Central Appalachian Mountains
Stephanie Augustine, Christopher Rota

Canada Warblers (Cardellina canadensis) are a Nearctic-Neotropical migratory songbird that has exhibited apparent declines in abundance over recent decades. This species occupies a wide range of environmental conditions throughout their range but lack substantial data regarding elements driving variation in demography and the strength of population migratory connectivity. The aims of this research are (1) determine the relationship between demography and environmental conditions, including shrub cover and riparian areas, along an elevation gradient and (2) ascertain migratory route and wintering locations of a population of Canada Warblers breeding in the central Appalachian Mountains. Our research takes place at six study sites ranging in elevation from 526 – 1282m spanning an approximate 130km north-south gradient within the Monongahela National Forest in West Virginia. We will estimate apparent survival with a three-year mark recapture study; in 2019 and 2020 a total of 211 birds were uniquely color-banded. To determine migration strategies, in 2020 we also deployed 32 of the adult males with light-level geolocator tags. During the 2020 field season, we observed a 32% return rate of banded birds, with 73% of birds re-sighted within 100 m of their 2019 locations. Re-sight data collected in the 2021 field season will be used to account for interannual local movements and correct for detection probability to model true survival. We will also retrieve geolocators, which will elucidate patterns of population connectivity and establish a baseline for full annual cycle modeling of this species for the future.

Spatial Partitioning of Cassin’s Sparrow Breeding Pairs and Territorial Males
Edward Landi, Augustus Forrest, Claire Ramos, Nate Bickford

North American grasslands are one of the most threatened ecosystems in the world and grassland birds have experienced the largest declines. Many grassland bird species are understudied and much of their breeding ecology and conservation status is unknown due to their elusive behavior. Grassland species like Cassin’s Sparrows (Peucaea cassinii) can breed in high densities in suitable habitat. High densities may lead to fitness cost incurred by intersexual competition in breeding pairs and intrasexual competition between territorial males. Spatial partitioning of home ranges may be used to reduce competition. To address this hypothesis, we evaluated the movement patterns of male and female Cassin’s Sparrows of the same breeding pair and between males on neighboring territories during the summer of 2020 and 2021. We used an automated telemetry system and solar powered LifeTags by Cellular Tracking Technologies to track locations of 46 Cassin’s Sparrow in Southeastern Colorado. We measured competition by the amount of home range (AKDE) overlap and the size of a conditional distribution of encounters (CDE) between competing individuals. We estimated vegetation structure inside the core area of a CDE for each individual in a breeding pair and neighboring territorial males that interacted. To measure resources under competition. Our results show that overall individuals have a high percentage of overlap and breed in high densities. All individuals had an average overlap of 48% between their AKDE home range with other individuals. This overlap is lower than other members of its genus like breeding Bachman’s Sparrows (Peucaea aestivalis) by 20% percent.  This shows Cassin’s Sparrows are reducing competition by spatially partitioning their territory to have less overlap. These results contradict previous studies that showed Male Cassin’s Sparrows do not overlap territories.  

Role of Female Space Use in Lek Dynamics of Translocated Lesser Prairie-Chickens
Carly Aulicky, David Haukos, Kent Fricke, Liza Rossi, Jonathan Reitz, Kraig Schultz

Translocation of male prairie grouse prior to releasing females is believed to retain birds at desired sites by bolstering or forming new leks. However, this method is based on an untested assumption that males are the dispersing sex in a lek breeding species despite increasing evidence indicates widespread, long-distance movement by females. Female-driven dispersal implies a different mechanism such as the hotspot hypothesis, which postulates males form leks following female space use and habitat constraints. We tested the hotspot hypothesis in shaping lek formation and stability of translocated lesser prairie-chickens (Tympanuchus pallidicinctus) in the Sand Sagebrush Prairie Ecoregion of Kansas and Colorado, USA, using the spatial movements of 72 GPS and 44 VHF equipped females. We used ArcGIS optimized hotspot analysis to identify significant clusters of female locations and evaluated where translocated males formed leks and the persistence of those leks. We found that intensity of space use by female lesser prairie-chickens drove lek size and leks formed in location clusters. We found the number of nesting attempts by females within a 5- to 2-km distance had the greatest influence on the persistence of leks into a subsequent year. Our findings show that visual obstruction constraints for quality nesting habitat and female space use drive placement and stability of leks, as expected under the hotspot hypothesis. Future translocation efforts should focus on female habitat constraints by creating quality nesting habitat to sustain long-term nest-site selection prior to releasing birds in order to encourage lek formation and persistence after translocation.

Habitat Selection and Breeding Ecology of Bachman’s Sparrow in a Wiregrass-Free Ecosystem
Mikayla Thistle, Jamie Dozier, Mark McAlister, Beth Ross

Through much of its range, Bachman’s Sparrow (Peucaea aestivalis) uses the wiregrass (Aristida spp.) dominant understory typical of longleaf pine (Pinus palustris) forest. The central South Carolina Coastal Plain, however, lies within the “wiregrass gap” where longleaf pine understories are absent of wiregrass and instead are dominated by bluestem grasses (Schizachyrium spp. and Andropogon spp.), bracken fern (Pteridium aquilinum), and shrubs. Habitat use of Bachman’s Sparrow in this region has yet to be studied and declining Bachman’s Sparrow populations necessitate a better understanding of habitat selection processes and population dynamics across regional habitat types. The goal of this study was to describe breeding season habitat use and breeding ecology of Bachman’s Sparrow in the unique wiregrass-free longleaf pine ecosystem of Tom Yawkey Wildlife Center, Santee Coastal Reserve, and Washo Reserve, South Carolina to inform best management practices for Bachman’s Sparrow. We conducted repeated visit point count surveys at 95 locations and used open N-mixture models to estimate the effects of habitat management and forest stand characteristics (e.g. prescribed burns, basal area, stem density) on Bachman’s Sparrow abundance, apparent survival probability, and recruitment rates during the 2020 and 2021 breeding seasons. We also located nests to identify vegetation composition and structure characteristics that Bachman’s Sparrows select for nest-sites. To determine if habitat selection in our study population was adaptive, we monitored nests and related nest-site selection to nest survival rates by comparing habitat characteristics related to selection with those related to survival. Bachman’s Sparrows selected nest-sites that had intermediate grass cover compared to available nest-sites; however, nest survival rates showed no clear relationship to any measured covariates. The results of this study can be used to inform region-specific management plans and restoration of degraded habitats, which often lack typical understory species like wiregrass, to increase Bachman’s Sparrow abundance and reproductive success. 

Variance in Clutch Size and Egg Morphology of Lesser Prairie-Chickens Across a Climate Gradient
Clint W. Boal, Sophie Morrise, David Haukos, Blake Grisham

Lesser prairie-chickens (Tympanuchus pallidicinctus) are distributed from southeast New Mexico to south-central Kansas. This range encompasses a temperature and precipitation gradient that is hotter and drier in the southwest to cooler and wetter in the northeast. We hypothesized lesser prairie-chickens may vary clutch sizes or egg morphology as an adaptation to local environmental conditions. We compared clutch sizes and morphometric characteristics of lesser prairie-chicken eggs from among study areas in Texas and Kansas. We used analysis of variance tests to compare clutch sizes, and egg metrics of length, width, volume, surface area, deviation from an ellipse, and mass. We also compared egg coloration and extent of speckling. Lesser prairie-chickens in Texas set significantly fewer eggs per clutch (mean 6.7 ± 1.75 SD) compared to those in Kansas (mean 10.3 ± 2.36 SD). We found eggs from the Texas study area were larger, with greater volume than any of the Kansas study areas, and had a greater mass than two of three Kansas study areas. Texas prairie-chicken eggs also had greater deviation from an ellipse than two Kansas study areas. Visual appearance also differed; Texas eggs were lighter toned in shell color but had a greater frequency of speckling than Kansas eggs. Our results suggest that lesser prairie-chickens in Texas put greater investment in fewer but larger eggs per clutch. The lower surface to volume ratios of larger eggs translates to reduced evapotranspiration loss of moisture and reduced heat gain compared to smaller eggs. The diffuse darker speckling against a lighter background may serve to improve camouflage of eggs while reducing heat absorption compared to darker toned eggs. It appears that lesser prairie-chickens in the southwestern extent of their distribution may be responding to the hotter and drier climate through modification of clutch sizes and egg morphology. 

Assessing Wild Turkey Occupancy Using Automatic Recording Units and Package Monitor
Janelle Ostroski, Jay Cantrell, Charles Ruth, Beth Ross

Wild turkey is a highly popular game species harvested primarily during the reproductive season, which has driven substantial efforts to understand patterns of springtime habitat use.    Gobbling activity and associated habitat selection has been increasingly assessed through the use of Automatic Recording Units (ARUs), yet post hoc processing of audio data has been time-intensive particularly due to false detection rates.  Gobbling activity has been studied in the South Carolina Coastal Plain, but data for the Upstate are lacking.  Our goals were to assess gobbler occupancy patterns using ARUs in conjunction with an alternative acoustic template finder, monitoR.  We deployed 38 ARUs throughout Upstate SC and collected daily 3-hour recordings from March 1 to May 30, 2019.  We used monitoR to create two audio templates of gobbles, serving as two independent “observers” in a traditional occupancy model framework, and automatically scanned recordings using these templates to generate detection/non-detection data. We created two templates to detect relatively soft and loud gobbles, resulting in different false positive rates for each template due to associated sensitivity.  We incorporated a suite of habitat and detection covariates (e.g., distance to water, elevation, template type) into hierarchical single-season occupancy models accounting for false positive rates and compared March and April models using Akaike’s Information Criterion.  Detection and false positive models incorporating template type and distance to water were ranked consistently higher (> 2 AICΔ) than other covariates.  The top-ranked model for March showed probability of false positives increasing closer to water sources, while the top April model demonstrated a positive correlation with occupancy and elevation.

Contributed Oral
Location: Virtual Date: November 3, 2021 Time: 3:00 pm - 4:00 pm