Conservation and Ecology of Birds III

Contributed Paper
ROOM: Room 140 – Aztec

10:30AM The Effects of Beetle-Induced Tree Death on Forest Songbird Diversity in the Western United States
William M. Janousek; Victoria J. Dreitz
In forest ecosystems, climate change can hinder management success by increasing the frequency and intensity of fire and insect outbreaks which cause massive tree die-offs and abrupt habitat change. Due to the challenge of monitoring all aspects of any ecosystem, resource managers use ecological indicators to gain insight into the health and status of ecosystems. Birds have been identified as an appropriate taxon for predicting changes in biodiversity and ecological integrity around the globe. We specifically focus on songbirds because they are ubiquitous and possess attributes that capture the complexity of forests as ecological indicators. We assessed the effect of bark beetle induced forest die-off on patterns of songbird diversity across six western states (ID, MT, WY, UT, CO, SD). We also examined the importance of the “conspecific neighborhood” in influencing species-level occurrence. This approach is motivated by the idea that individuals of a species aggregate around resources. It follows, that a species is more likely to occur in a patch surrounded by other occupied patches (the conspecific neighborhood). The need to incorporate measures of spatial autocorrelation in ecological studies has been well recognized but seldom applied in analytical methods that estimate multi-species demographics. Recent advances using Bayesian multi-species hierarchal models allow for measures of spatial autocorrelation to estimate species abundance and occurrence rates. We found an overall negative relationship between songbird diversity and the degree of beetle kill within a forest stand. We also observed an increase in the occurrence of bark-drilling insectivore and cavity nesting species, however any increase in the occurrence of these species was not strong enough to negate the community level decline in diversity. Our results indicate large-scale beetle outbreaks alter the food-resource base for both primary and secondary consumers as well as the structure and composition of forest vegetation.
10:50AM Monitoring Avian Response to Explosive Testing, Wildland Fire Mitigation Measures, and Precipitation
Jesse Berryhill; Charles D. Hathcock; Brent Thompson
A multiple -year study was initiated to investigate the effects of explosives testing on avian communities during the breeding season (May – July) at Los Alamos National Laboratory (LANL) in north-central New Mexico. Observations made using point count surveys along with nest box monitoring at three test sites were analyzed and compared to control sites of similar habitat. Point count survey data were analyzed for: abundance (# of birds/hour), diversity (Shannon index), and grouping into feeding guilds (granivore, insectivore, and omnivore). Nestbox occupancy data were compared against a LANL-wide avian nestbox network. Within four years of data collection analysis has shown there have been slight changes to the avian communities between study sites, control sites, and between years. A factor identified by coupling this dataset with a robust weather and precipitation record frames how varying precipitation levels may also be influencing community shifts. Another factor which may be influencing shifts is the continued removal of large woody vegetation for fire mitigation purposes at one of the sites. These data suggest that explosives testing has not negatively affected avian communities, but analysis is ongoing to examine wildland fire mitigation measures and precipitation patterns to determine their level of impact on the local bird communities.
11:10AM Migratory Behavior and Dispersal of Burrowing Owls throughout North America
Courtney J. Conway; David H. Johnson; Carl G. Lundblad; Julie L. Conley
Burrowing owls (Athene cunicularia) have declined throughout their range, and identifying the potential cause(s) of those declines requires better knowledge of migratory routes, wintering locations, and breeding dispersal. To provide this information, we deployed geolocators on 296 owls and solar-powered satellite transmitters (PTTs) on 34 owls at locations throughout the U.S. Eighteen percent of the geolocators and 53% of the PTTs produced useful data on migration behavior. All owls that bred in OR and WA wintered in the U.S. and migratory behavior differed between sexes: females wintered in CA whereas most males wintered in WA. In contrast, most owls from interior states migrated to Mexico for the winter. Distance between breeding and wintering sites varied from 983-3250 km. Owls had stronger site fidelity to their wintering locations than to their breeding sites (P=0.05): the average breeding dispersal was 34.7 km (range 0-164km) whereas the average distance between consecutive wintering locations was only 0.1 km (range 0-0.8km). We documented substantial variation among individual owls in the time spent migrating but no difference between time spent during spring and fall migration: 6-57 days on fall southbound migration (mean 22.9 days) and 6-51 days on spring northbound migration (mean 21.6 days). Over 90% of the owls that nested in (and migrated from) CO, WY, SD, NE, and MT took a multi-day break from migration in a confined swath of land between Amarillo and Stockton, Texas (with most of these stopovers near Lubbock, TX). The median date that females began their fall (southbound) migration was 9 Oct (range 17 Sep – 27 Oct), and the median arrival date that females arrived at their nesting location in the spring was 7 Apr (range 21 Mar – 5 May). Our results identify important stop-over and wintering locations that may be important for continent-wide burrowing owl conservation.
11:30AM Scavenger Removal of Bird Carcasses at Simulated Wind Turbines: Does Carcass Type Matter?
Travis L. DeVault; Thomas W. Seamans; Kimberly E. Linnell; Dale W. Sparks; James C. Beasley
Efforts to understand the ecological impacts of wind energy development include bird mortality studies at operating wind farms. Mortality estimates obtained in these studies are corrected for scavenger bias, which is quantified by placing bird carcasses under turbines and documenting their persistence over time. Most studies rely on farm-raised birds as surrogates because carcasses of wild birds are difficult to obtain. However, the use of surrogates could lead to inaccurate quantification of scavenger bias if carcasses persist at different rates across species. We assessed scavenger removal of American kestrel (Falco sparverius), red-tailed hawk (Buteo jamaicensis), northern bobwhite (Colinus virginianus), rock pigeon (Columba livia), and brown-feathered domestic chicken (Gallus gallus) carcasses (n = 52 for each species) at 10 simulated wind turbine sites in northern Ohio during 13 2-week rounds between 2 July 2014 and 8 July 2015 using camera traps. We investigated the effects of carcass type (i.e., species), carcass mass, round number, air temperature, and habitat type (grassland or forest) on several measures of carcass persistence. All predictor variables were included in best-fit logistic regression models predicting evidence of scavenging by vertebrates, but only carcass type was included in the best-fit model predicting complete carcass disappearance. The number of carcasses scavenged by vertebrates ranged from 18 (34.6%) for American kestrels to 34 (65.4%) for chickens, and the number of carcasses that were completely missing at the end of rounds ranged from 7 (13.5%) for red-tailed hawks to 35 (67.3%) for northern bobwhites. Carcass type also influenced the vertebrate species that scavenged carcasses. For example, turkey vultures (Cathartes aura) scavenged 12 chicken carcasses but only 4 carcasses from all other species combined. Our results suggest that the use of surrogates to quantify carcass removal could lead to inaccurate quantification of scavenger bias, which could strongly affect mortality estimates.
11:50AM Woodpecker Nest Survival in Relation to a Mountain Pine Beetle Outbreak
Victoria Saab; Matthew Dresser; Quresh Latif; Jay Rotella; Jonathan Dudley
Mountain pine beetle (Dendroctonus ponderosae; MPB) outbreaks in western North American coniferous forests are increasing in size and severity. Understanding of wildlife population responses to MPB epidemics is needed to inform habitat conservation strategies. We monitored woodpecker nesting for Northern Flicker (Colaptes auratus), Red-naped Sapsucker (Sphyrapicus nuchalis), and 3 bark-foraging species (Picoides spp.) in a dry mixed conifer forest of Montana, U.S.A, over a 12-year period (2003-2006, 2009-2014), during which an MPB outbreak peaked in 2008. We analyzed daily survival rate (DSR) in relation to MPB severity and timing along with other covariates. We found little evidence for DSR relationships with MPB timing (pre- versus post-outbreak) or severity (annual and cumulative pine tree mortality at 0.81- and 314-ha scales). In contrast, we found stronger evidence for nest survival relationships with additional covariates identified in other studies (temperature, nest height, and nest tree diameter). Additionally, relative densities of hatched nests for Picoides spp. increased following the outbreak although nest survival remained relatively constant. Our findings suggest nesting woodpeckers, particularly bark-foraging species, respond positively to MPB outbreaks. Outbreaks, however, appear to elicit positive numerical responses by woodpeckers without necessarily affecting nest survival.


Contributed Paper
Location: Albuquerque Convention Center Date: September 25, 2017 Time: 10:30 am - 12:10 pm