Demographic risk to eagles from anthropogenic causes of death TODD KATZNER, U.S. GEOLOGICAL SURVEY David Nelson, University of Maryland, MD, USA Melissa Braham, West Virginia University, WV, USA Adam Duerr, Bloom Biological, PA, USA Tricia Miller, Conservation Science Global, NJ, USA Renee Culver, NextEra Energy, CA, USA Andrew DeWoody, Purdue University, IN, USA U.S. Department of the Interior U.S. Geological Survey
Anthropogenic causes of death
Assess how birds die
Can’t simply study birds people find – non-random and biased towards certain processes.
Published study of 400 telemetered eagles (FWS 2017)
Cause of death known for 97
Bayesian model predicts rates
Anthropogenic causes of death
Natural causes of death
Starvation/disease = 22%
Fighting with other eagles = 11%
Natural Injury = 7%
Drowning = 2%
Predation (eaten) = 1%
Anthropogenic causes of death
Anthropogenic causes of death
Poisoning (non-lead) = 17% Shot = 15% Collision (wind, vehicles) = 9% Electrocution = 8% Trap = 4% Lead toxicosis = 3%
Anthropogenic causes of death
63% of fatalities of adults caused by humans
34% fatalities of first year birds caused by humans
Annual eagle survival rates would be 10% higher without humancaused fatalities
Example: Altamont Pass Wind Resource Area
Altamont is one of oldest facilities in the world
Very large
Kills many birds of prey each year, including many golden eagles
once up to 7,000 turbines currently <5,000 operational
Golden Eagles 101
Demography 101
Nt = N(t-1) + Bt â&#x20AC;&#x201C; Dt + It â&#x20AC;&#x201C; Et N = population size at time t B = # births at time t D = # deaths at time t I = # of immigrants at time t E = # of emigrants at time t
GOEA = k selected, B & D low
GOEA = mobile, I & E may be high
Research Question
What is the origin of eagles killed at Altamont? What does that mean for eagle demography?
If eagles killed are locals, implies high Bt If eagles killed are from elsewhere, implies high It
Methods
Answer three key questions about Altamont killed golden eagles: 1. What is their age? 2. How many genetic populations do they represent? 3. Where did they grow their feathers?
Data collected through study of dead golden eagles 1. Individuals photographed and aged (molt patterns). 2. Genetic analysis (microsatellites, SNPs). 3. Feather samples for stable isotope analysis (δ2H, etc.).
Methods - Genetics
Collected feather and organ tissue samples from turbinekilled eagles
Genotyped eagles
9 microsatellite loci established sexing primers 159 nuclear SNPs 1 sexing SNP 2 mtDNA SNPs
Methods - Stable Isotopes Light water:1H1HO δ2H : more negative
Heavy water: 1H2HO δ2H: more positive
Methods - Stable Isotopes
Turbine-killed & known-origin refs δ2H : 3 body feathers
Convert feather- δ2H to precip.- δ2H (Lott & Smith 2006)
Geospatial model to calculate likelihood-of-geographic origin map based on δ2H (Bowen et al. 2014) Monte Carlo simulation to estimate if bird local or non-local
Results
Age: n = 49 DNA: n = 62 (52 SNP) Isotopes: n = 66 44 known origin references
Of the 49 aged
HY = 1 2Y = 15 3Y = 16 4Y = 2 A4Y = 15
Results - genetics
STRUCTURE
K = 1 thru 5 suggests that K = 1 (one population)
microsats & SNPs = same message
Results – stable isotopes
δ2H of May – Aug precipitation
location of 44 reference eagles
Results â&#x20AC;&#x201C; stable isotopes
comparison of known-location and isotope-inferred summering grounds isotope models were reasonable predictors of origin
Results â&#x20AC;&#x201C; stable isotopes
some birds clearly grew feathers locally
others clearly grew feathers non-locally
Example – golden eagles at APWRA 17 of 66 birds = “nonlocal”
minimum distance up to 837km
Probability of being non-local not linked to: age month sex
Results - demography
Models predict that ~11% of GOEA should be 2Y In fact, 30% of birds killed are 2Y
Nearly impossible to model a population whose age structure replicates killed birds
Together with isotope data, suggests that population sustained by immigration of 2Y-4Y birds
Origins of birds at APWRA
Eagles at APWRA are one genetic population
~25% of the birds killed at APWRA are â&#x20AC;&#x153;non-localâ&#x20AC;?
Turbine-associated mortality at APWRA is additive
Anthropogenic causes of death
APWRA influences continental-scale demographic processes
Illustrates important considerations for of anthropogenic sources of death
Can have far-reaching consequences
• Acknowledgments • Funding: BLM, USDoE, DFG/DFW, FWS, etc.