Raptors

Contributed Oral Presentations

SESSION NUMBER: 81

Contributed paper sessions will be available on-demand for the duration of the conference, then again at the conclusion of the conference.

 

Exploring Sandhill Crane Movement on the Wintering Grounds: A Visualization and Decision Support Tool
Quentin R. Hays; Daniel P. Collins; Jason D. Carlisle; Andrew T. Tredennick
Each year, approximately 45,000 sandhill cranes winter in the Middle Rio Grande Valley (MRGV) of New Mexico; many of these birds comprise the Rocky Mountain population of greater sandhill cranes. Of management interest, the MRGV has been identified as the most important wintering area for this population. Like many arid or semi-arid systems, the MRGV is heavily influenced by long-term drought and anthropogenic disturbance. Recent research has helped elucidate how disturbance regimes and land use changes influence habitat selection by wintering sandhill cranes in the MRGV, but fine-scale movement patterns have not been fully explored. We used GPS telemetry data from 81 sandhill cranes collected between 2014-2020 to examine diurnal movement paths and flight heights of cranes in the MRGV. We defined movement paths as the connection between points that occurred consecutively in time, and used flight height information at each point to estimate the movement height distribution of all cranes at 500-meter latitudinal intervals in the north-south MRGV study area. We fit a non-parametric, smoothing spline model to the data that predicts flight heights according to the density of points at different heights. We fit this spline model 1,000 times, using a 5,000-observation sample from the data each time, to develop a distribution of flight height estimates at each 500-meter latitudinal interval. We were then able to estimate the probability that a movement across any latitudinal interval occurred at a certain height. Finally, we developed an interactive movement explorer web app using the ‘Shiny’ R package so users could explore crane passage rates and flight height distributions at any 500-meter interval in the MRGV. Users can also define hypothetical exposure zones, representing a potential high-voltage transmission line across the Rio Grande, to help support decision making.
The Trade-Off between Biologist Safety and Eagle Nest Surveys
Rhett E. Good; Clayton Derby; Wally Erickson; David Young; Todd Mattson
The U.S. Fish and Wildlife Service developed Eagle Conservation Plan Guidance in 2013 for addressing risk at wind-energy projects, including methods for completing eagle nest surveys. The guidance includes the definition of project specific or regional mean inter-nest distances, and recommends conducting nest surveys up to 10-miles from wind turbine locations when existing data are insufficient to define inter-nest distances. Wind-energy is a rapidly growing energy source, and wildlife agencies often recommend surveys be completed within 10-mi of projects. Most wind-energy projects are surveyed from helicopters or small airplanes due to the large survey area, and to increase the probability of detecting nest locations. Aerial surveys require low flight heights, and crashes from aerial surveys are the leading on-the-job cause of death for wildlife biologists. Extensive telemetry and nest location data collected since 2003 show that bald eagle territories are much smaller than golden eagles and that both species spend most of their time in close proximity to nests (e.g. < 2-mi). Given this, surveys beyond 2-mi from wind projects have very limited value in risk and impact assessments. Smaller survey areas provide adequate information for assessing risk to eagles, and would result in fewer hours needs for aerial surveys. The potential safety risk to biologists needs to be prioritized by wildlife agencies, wind-energy companies, and consulting firms when defining survey areas. We provide two recommendations for allowing credible assessments while reducing need for aerial surveys: 1) Existing data can be used to define inter-nest distances, decreasing the amount of area required for searches; and 2) Drones should be allowed for surveys when visibility is limited to conduct surveys or to check nest occupancy.
Documenting Bald Eagle Nests on Artificial Structures in Florida
Shawnlei F. Breeding
Objectives: As natural habitat gives way to developed land, Bald Eagles (Haliaeetus leucocephalus) in Florida are beginning to nest on cell towers and other artificial structures. Roughly 20% of the nests currently monitored by the Audubon EagleWatch Program are on artificial structures. EagleWatch is investigating what impact this choice may have on Florida’s eagles through both nest data collection and a multi-year auxiliary banding study. The goal of the auxiliary banding study is to determine if the nest structure type a chick hatches in influences the type of structure it chooses as a breeding adult. Understanding what impact nest site choice may have on the long-term productivity and sustainability of the eagle population in Florida will help guide future management plans for this species. Methods: Bald Eagle nest data is collected by community science volunteers during the nesting season following a set protocol. End of season nest productivity data is analyzed by nest structure type. Starting in 2017, eaglets treated and released by the Audubon Center for Birds of Prey are given a colored auxiliary band with color based on hatching structure. Banding statistics and resight information are gathered each season. Results: Analysis of five years of nest productivity data indicates that eagles nesting on artificial structures are as successful as eagles nesting in trees. The auxiliary banding study is in its fourth year and has banded 43 juveniles to date. Band resight data has been collected on 4 birds, documenting post-fledging survival and dispersal. Conclusions: Nests on artificial structures may offer unrecognized benefits to nesting success, providing alternative nest sites to Florida’s population of Bald Eagles. Juvenile eagles banded in the inaugural year of the auxiliary banding study will reach breeding age in 2021, which will be the first year for potential nest site choice data.
A Multi-Species Dynamics Hierarchical Distance Sampling Model for Analysing Variability of Populations of Raptors
Edwige Bellier; James A. Martin; Justin Rectenwald; Clay Sisson; Theron M. Therhune
Understanding how the populations in ecosystems respond to environmental fluctuations is crucial in ecology. The dynamics of the different species of a community is essential for the ecosystems as they support the functioning of food webs and maintain biodiversity. The fluctuations of abundances and populations growth are rarely analyzed simultaneously despite the importance of the dynamics of the different species for keeping going ecosystem functioning. We developed a novel multi-species model grounded on a multi-species hierarchical distance sampling Bayesian framework that we extended to include population dynamics effects. The model estimates both community-level and taxon-level parameters related to dynamics, abundances, detection probability, and environmental stochasticity. We used this model to analyze the variability of populations of a community of raptors from long-term monthly time series collected by line-transect surveys at three localities in Georgia. The raptor community was composed of accipiters (sharp-shinned hawk, Accipiter striatus, and Cooper’s hawk, Accipiter cooperii), buteos (red-tailed hawk, Buteo jamaicensis, and red-shouldered hawk, Buteo lineatus) and owls (great horned owl, Bubo virginianus, and bared owl, Strix varia). Missing distance sampling data can be included in the analyses by simulating taxon-specific distance sampling data. Abundances and populations growth of the different taxons present strong interannual variations as well as seasonal variations. Including environmental stochasticity in population growth and detection probability improved the goodness-of-fit of the model. Our taxon-specific abundances and population dynamics estimates can be useful to analyze taxon-specific effects of variability of the weather, investigate taxon-specific interactions across different trophic levels, and to mitigate ecosystem-based conservation measures.
Assessing the Influence of Telecommunication Towers on Osprey Nesting Productivity and Behaviors in Western Kentucky
Gage Barnes; John Hewlett; Kate Slankard; Loren Taylor; Andrea Darracq
Osprey (Pandion haliaetus) nests located on telecommunication towers (TCTs) are approximately 3-8 times higher than natural or constructed nests. Consequently, nestlings reared on TCTs may be exposed to harsher weather conditions and ultimately have lower survival rates. Additionally, adults may use more energy during food provisioning because of TCT heights, which could influence foraging or nest guarding behaviors. The objective of our study is to evaluate the influence of TCTs on Osprey nest productivity, adult foraging, and nest guarding behaviors. We observed 30 Osprey nests (TCTs; [n=11], navigation daymarkers [DMs; n=10], natural substrates [NATs; n=9]) from aircraft, vehicle, or on foot. To assess differences in adult behaviors and nest success and productivity, we monitored each nest for adult foraging and nest guarding behaviors and the number of successful fledglings produced throughout the 2019 breeding season. Nests on DMs received 2 to 2.6 times more fish than nests on NATs and TCTs, respectively. Though not significant, DM nest success was 22.2% and 14.2% greater than NATs and TCTs, respectively. We hypothesize that the potential costs associated with TCT height may be counteracted by reduced human disturbances. Though DMs had high rates of human disturbance, increased provisioning of fish to offspring may offset these costs and partially explain the greater nest success we observed at nests on DMs. Consequently, there may be a trade-off between intensity of human disturbance and fish provisioning.

 

Virtual
Location: Virtual Date: Time: -