Avian Ecology & Management III

Contributed Paper
ROOM: HCCC, Room 23

8:10AM Vulture Nonlinearly Increase Carrion Consumption with Increasing Carrion Biomass
Carolina Baruzzi; Brandon Barton; Heather Jordan; Jeffery Tomberlin; Michael Cove; Marcus Lashley
Resource pulses can affect population dynamics and animal behavior and responses to resource pulses may vary depending on the magnitude of the pulse. Mass mortality events, or massive pulses of carrion resources into ecosystems, are common in nature and may be increasing due to climate change. Although vultures are obligate vertebrate scavengers and are known to provide a key ecosystem service in recycling carrion nutrients, how vultures respond to extreme pulses of carrion during mass mortality events is unknown. We hypothesized that increasing carrion biomass would numerically satiate vultures, but plasticity in vulture feeding and grouping behavior could allow carrion consumption to continue to increase with carrion pulse magnitude. To test this hypothesis, in July 2016 we deployed increasing carrion biomass (i.e. 25, 60, 180, 360, and 725 kg) in five study plots (i.e. 5m diameter plots). Plots were randomly selected and more than 1 km apart. Vulture behavior was observed with camera traps, from which we recorded number of individuals per group and the proportion of time individuals spent feeding. Vultures linearly increased group size and time spent at each site with increasing biomass while vulture consumption increased in an exponential nonlinear fashion because of changes in individual foraging behavior. As biomass increased, individual vultures spent an increasing proportion of time at the site foraging on carrion. These data indicate that plasticity in vulture behavior may play an important role in maintaining the ecosystem service they provide during extreme pulses of carrion from mass mortalities of wildlife.
8:30AM Estimating Prescribed Fire Effects on Semidesert Vegetation Components Important to the Masked Bobwhite Quail (Colinus Virginanus Ridgwayi) Using a 30 Year Landsat Derived Fire History Data
Emily L. Yurcich
Prescribed fire plays a vital role in restoring vegetation and fuel bed conditions characteristic of frequent fire regimes in southwestern semidesert grasslands. However, current fire management activities implemented at the local-to landscape-scales must be compatible with specific habitat requirements for threatened and endangered birds. The Buenos Aires National Wildlife Refuge (BANWR) in southern Arizona was established in 1985 to provide habitat for threatened and endangered plant and animal species, with primary emphasis on the critically endangered masked bobwhite quail (Colinus virginanus ridgwayi). Masked bobwhite are known to occupy semidesert grassland sites of moderate elevation (240-760m) with abundant grass cover and seed producing plants, a high diversity of forbs and interspersed woody plant cover. I used BANWR fire perimeters to examine the effect of fire frequency over the last 3 decades on vegetation characteristics. Multivariate analyses indicate that semidesert vegetation composition on plots is significantly different among fire frequency strata. Areas with high fire frequency were strongly correlated with high fine-fuel biomass dominance by Eragrostis lehmanniana, an invasive perennial bunch grass introduced from South Africa in the 1930s. Areas of low to moderate fire frequency may favor a greater abundance of native plants or lack site conditions suitable for E. lehmanniana.
8:50AM Influence of Individual Heterogeneity on Lesser Prairie-Chicken Population Persistence
Daniel S. Sullins; Beth E. Ross; David A. Haukos
Population stability emerges from complex interactions operating at multiple levels. Current population modeling techniques strive to account for such interactions by incorporating lower level vital rates from multiple life stages to estimate overall population growth rates (λ). This reductionist approach can identify survival bottlenecks and contributions to λ but the accuracy of population growth projections have been questioned. One way in which models may fail to estimate true λ could be due to not incorporating individual heterogeneity in vital rates. We assessed the influence of individual heterogeneity by simulating populations with varying degrees of correlation among survival and fecundity per individual. Our main goal was to examine the emergence of a stable population when a few long living individuals are also most reproductively successful. In the simulations, mean annual survival and fecundity rates were kept constant at the population level while correlation of annual female survival and fecundity was varied from -0.9 to 0.9 among 100 individual-based model simulations. Our results indicated a strong influence of correlated vital rates on λ when positive correlation was simultaneously increased with variance. Accurate projections of lesser prairie-chicken populations will require a stronger understanding of the variability and correlation of vital rates among individuals.
9:10AM Tracking Under-Studied Songbirds in the Desert: the Post-Fledging Period of Gray Vireos at Sevilleta National Wildlife Refuge, New Mexico
Sarah E. Fischer; Kathy Granillo; Henry M. Streby
Gray Vireos (Vireo vicinior) are short-distance migratory songbirds that breed primarily in piñon (Pinus spp.) -juniper (Juniperus spp.) systems in the southwestern United States and northwestern Mexico. These systems are well-studied and are heavily managed for game species and agriculture (e.g., juniper chaining). Gray Vireos and other songbirds that rely on these systems are relatively under-studied, presenting challenges to informing and implementing habitat management plans. Additionally, most studies of Gray Vireo demography focus on the nesting stage (i.e., nesting success as a measure of productivity). However, incorporating data from the post-fledging period and other stages of the annual cycle is essential to determine full-season productivity and habitat associations, as well as potential limiting factors to population growth. We monitored nests from 2016-2018 at Sevilleta National Wildlife Refuge in central New Mexico, USA. Nest success ranged from 24-25% and all nests were in one-seed juniper (J. monosperma). Brown-headed Cowbirds (Molothrus ater) parasitized 38-43% of Gray Vireo nests in those years. In 2017 and 2018, we used radio telemetry to track the daily movements of Gray Vireo fledglings to determine post-fledging space use, survival, and habitat features associated with those parameters. Fledgling survival was ~66% during the dependent stage (i.e., between nest departure and independence from adult care). The mean distance between daily movements was 241 m (± 235 SD), and the maximum observed daily distance was 1.4 km; these daily distances increased with fledgling age. Gray Vireo fledglings used one-seed juniper (J. monosperma) during 85% of observations (n=504), which may have implications for management. Like other fledgling studies, the majority of mortality occurred during the first week post-fledging. Our study highlights the importance of monitoring fledgling songbirds when considering full-season productivity and management decisions.
9:30AM Using Pentosidine and Hydroxyproline to Predict Age and Sex in an Avian Species
Brian S. Dorr; Randal S. Stahl; Katie C. Hanson-Dorr; Carol A. Furcolow
All living organisms are subject to senescence accompanied by progressive and irreversible physiological changes. The error damage and cross-linking theories suggest that cells and tissues are damaged by an accumulation of cross-linked proteins, slowing down bodily processes and resulting in aging. A major category of these cross-linked proteins are compounds called advanced glycation end products (AGEs). We investigated the relationship between accumulation of the AGE, pentosidine (Ps), and hydroxyproline (HYP) a post-translationally modified amino acid, with age, sex, and breeding status (breeder/ nonbreeder) from skin samples of known age (i.e., banded as fledglings), free-ranging Double-crested Cormorants (Phalacrocorax auritus, Lesson 1831). We developed multivariate models and evaluated the predictive capability of our models for determining age and breeding versus nonbreeding birds. We found significant relationships with Ps and HYP concentration and age, and Ps concentration and sex. Based on our two-class model using Ps and HYP as explanatory variables, we were able to accurately determine whether a cormorant was a breeder or nonbreeder in 83.5% of modeled classifications. Our data indicate that Ps and HYP concentrations can be used to determine breeding status of cormorants and potentially age of cormorants although sex-specific models may be necessary. Although the accumulation of Ps explained the greatest amount of variance in breeding status and age, importantly, Ps covaried with HYP and combined improved prediction of these demographics in cormorants. Our data support the error damage and cross-linking theories of aging. Both Ps and HYP increase predictably in cormorants and are predictive of age and breeding status. Given the ubiquity of these biomarkers across taxa, their use in estimating demographic characteristics of animals could provide a powerful tool in animal ecology, conservation, and management.


Contributed Paper
Location: Huntington Convention Center of Cleveland Date: October 11, 2018 Time: 8:10 am - 9:50 am