🟢 Research Era: 2011-Present
☠️ How Golden Eagles Are Killed in America
TL;DR- 70%+ of golden eagle deaths are human-caused (Millsap 2022, Bayesian model of 3,594 band recoveries)
- Top causes: illegal shooting ~700/yr, power lines ~504/yr, wind turbines ~270/yr (growing fast) and rising
- All figures are modeled estimates with wide confidence intervals — see full paper for uncertainty ranges
One of Millsap's most important contributions is documenting exactly how golden eagles die. Using banding data, telemetry, and recovery records across the western United States, his 2022 study "Age-Specific Survival Rates, Causes of Death, and Allowable Take of Golden Eagles in the Western United States" provides the definitive answer: most golden eagle deaths are caused by human activities.
⚡ The Shocking Finding
Over 70% of golden eagle deaths are attributed to human impact—either direct killing through shooting or indirect deaths from human infrastructure and activities.
Annual Golden Eagle Deaths by Cause
📐 Primary Source — Millsap et al. 2022
Full citation: Millsap, B.A., et al. (2022). "Age-Specific Survival Rates, Causes of Death, and Allowable Take of Golden Eagles in the Western United States." Ecological Applications, 32(3), e2544. DOI: 10.1002/eap.2544 Peer-Reviewed
Methodology: Bayesian mark-recapture analysis using 3,594 band recoveries and 357 radio/satellite-tagged eagles across the western U.S., 1997–2017. Cause-of-death categories assigned from necropsy records, recovery notes, and transmitter signal data.
Caution: All figures are modeled central estimates; 90% credible intervals in the published study are wide. Numbers shown here are rounded approximations suitable for general communication, not regulatory use. Consult the full publication for precise values and uncertainty ranges. ~ Model Estimate
Wind-turbine figure only: Gedir, J.V., et al. (2025). "Estimated golden eagle mortality from wind turbines in the western United States." Biological Conservation. DOI link Peer-Reviewed
~700
ILLEGAL SHOOTING
20% of post-first-year deaths
~600
COLLISIONS
Vehicles, power lines, wind turbines
~500
ELECTROCUTION
Power pole contact
~400+
POISONING
Lead & rodenticide
🔫 Illegal Shooting - One of the Two Largest Human-Caused Killers
The Problem:
- ~700 eagles shot annually (20% of all post-first-year deaths)
- Shooting and power-line electrocution are the two largest human-caused causes of death
- Illegal under the Bald and Golden Eagle Protection Act (BGEPA)
- Difficult to detect and prosecute
🚗 Collisions - The Hidden Killer
Multiple Collision Types (~600 annually):
- Vehicles: Eagles hunting roadside prey struck by cars
- Power Lines: Collision with transmission lines and towers
- Wind Turbines: Blade strike at wind farms (roughly 12% of human-caused deaths)
- Structures: Buildings and other human infrastructure
Wind Turbines: The Overblown Threat
While wind turbines receive significant media attention, they represent roughly 12% of human-caused golden eagle deaths. However, in concentrated wind energy areas, impacts can be locally significant.
⚡ Electrocution — Power Pole Deaths
📐 Primary Sources — Electrocution Section
Millsap et al. (2022), Ecological Applications 32(3) — modeled annual electrocution mortality estimate. Peer-Reviewed
Mojica, E.K., et al. (2018). "Review and synthesis of research investigating golden eagle electrocutions." Journal of Wildlife Management 82(5):939–951. DOI: 10.1002/jwmg.21412 — comprehensive literature review; identifies 8 risk factors, distribution poles as primary hazard. Peer-Reviewed
Dwyer, J.F., Harness, R.E., & Eccleston, D. (2017). "Avian Electrocutions on Incorrectly Retrofitted Power Poles." Journal of Raptor Research 51(3). View Study — evaluated 52 poles marked "retrofitted" where eagles still died. Peer-Reviewed
Scale of the Problem Millsap 2022 Mojica 2018
- ~504 golden eagles electrocuted annually in the U.S. (Millsap et al. 2022, modeled estimate; 95% credible interval: 124–1,494) — roughly 26% of all anthropogenic mortality
- Juveniles electrocuted at nearly twice the rate of subadults or adults — they haven't learned which poles are dangerous
- Primary hazard: medium-voltage distribution lines (4–34.5 kV), not high-voltage transmission towers — conductor spacing on distribution poles is narrow enough to bridge an eagle's wingspan
- Pole configuration is the #1 risk factor; age is #2. Other factors: land cover, topography, prey availability, season, weather, and behavior
- Eagles prefer isolated poles in open terrain as hunting perches — even sparse pole networks in prime eagle habitat are dangerous
- 1978–1998 five-state survey (NE, KS, CO, WY, Dakotas): 2,060 raptor deaths recorded; 50% electrocuted; 75% of electrocuted birds were golden eagles
📍 Worst Documented Hotspot: Wyoming — Bighorn Basin
Wyoming is the most comprehensively documented electrocution problem area in the United States:
- 1,000+ documented eagle electrocutions in Wyoming since 1991
- 480+ of those in the Bighorn Basin alone — the densest documented concentration in the country
- Between January 2007 and mid-2009: 232 golden eagles, 46 hawks, 59 owls, and ~200 other birds electrocuted on PacifiCorp/Rocky Mountain Power lines in Wyoming
- Most deaths occurred on poles with poorly configured lines or complex intersections of equipment — the fix is spacing lines 5 feet apart and insulating connections, but older infrastructure was never upgraded
⚖️ Documented Utility Enforcement Cases
⚡ Show documented utility enforcement cases (6 cases)
| Utility |
Location |
Year |
What Happened |
Outcome |
| PacifiCorp / Rocky Mountain Power |
Bighorn Basin, Wyoming |
2009 |
232+ golden eagles, 46 hawks, 59 owls killed on unfixed poles. 1,000+ total documented deaths in WY since 1991 on various utility lines. |
34 misdemeanor counts (MBTA); $510K fine; $900K conservation restitution; $9.1M over 5 years to retrofit poles. 400+ poles fixed around Rock Springs & Cody after investigation. Gov't Record |
| Moon Lake Electric Association |
NW Colorado / Utah oilfield |
1999 |
First-ever criminal prosecution of a utility under MBTA + BGEA. 17 hawks and eagles electrocuted 1995–1997 on 2,450 unfixed oilfield poles. |
$100K fine; 3 years probation; full pole retrofit required; comprehensive Avian Protection Plan mandated. DOJ Record |
| Xcel Energy |
12 states (mid-section U.S.) |
2002 |
Documented eagle and hawk electrocutions across system; DOJ historic agreement. |
Agreed to evaluate and retrofit 90,000+ miles of transmission lines; comprehensive pole-by-pole review mandated. DOJ Record |
| Atlantic City Electric / PSE&G |
Cumberland County / Maurice River, NJ |
2020 (reported) |
34 bald eagles electrocuted 2015–2019 — #1 cause of raptor death in the area. Atlantic City Electric identified 21 high-risk line segments and 80 new eagle roosts but was still mapping exposure, not completing fixes. |
Ongoing mitigation; no criminal prosecution filed as of 2020. Field Survey |
| NorthWestern Energy |
Montana (statewide) |
Ongoing |
Manages 28,000 miles of lines. Publicly stated it is "impossible to retrofit all power poles." Only retrofits when an incident is reported — no proactive inspection program. |
Avian Protection Plan filed with USFWS; reactive-only approach. Utility Self-Report |
| La Plata Electric Assoc. (LPEA) |
La Plata & Archuleta Counties, SW Colorado |
2024–2025 |
100 high-risk poles identified but still unfixed going into 2025. Awarded Eagle ILF Program grant (Dec 2024) to retrofit these specific poles — work scheduled for 2025. |
ILF grant-funded retrofit underway. Confirms the scale of known-but-unfixed poles even among proactive utilities. USFWS ILF Program |
🚨 The "Incorrectly Retrofitted" Problem — Dwyer et al. 2017
Perhaps the most damning finding in the electrocution literature: researchers examined 52 power poles officially listed as already retrofitted — and found eagles still dying on them. Three failure categories:
- Product design errors (9 poles, 6 golden eagles) — retrofit products didn't actually cover all energized components
- Mitigation plan errors (30 poles, 6 golden eagles) — plans simply omitted coverage of certain energized parts on the pole
- Application errors (13 poles, 5 golden eagles) — correct products installed incorrectly
The core problem: Retrofitting mistakes are only discovered after another bird dies. The industry has no proactive inspection protocol — they wait for a carcass to identify a failed retrofit. This means the true number of dangerous poles is larger than official "retrofitted" records suggest. Peer-Reviewed
2024 USFWS General Permit Rule — What Utilities Are (and Aren't) Required to Do Gov't / Federal Rule
Effective April 12, 2024, utilities that register for a general permit under the Bald and Golden Eagle Protection Act must:
- Reactive retrofit: Fix any pole where an eagle is electrocuted — enforcement is complaint-driven, not proactively inspected
- Proactive retrofit: Convert only 10% of known dangerous poles per 5-year permit period — meaning a utility with 10,000 dangerous poles can legally leave 9,000 of them standing through any given permit cycle
- 72-hour reporting: Report eagle electrocutions to USFWS Office of Law Enforcement within 3 days of discovery
- Avian-safe standard for new poles: 150 cm horizontal / 100 cm vertical separation between conductors — applies to new construction only, not existing infrastructure
- ILF loophole: Utilities may pay into the Eagle In-Lieu Fee Program (buy mitigation credits) instead of fixing their own poles — first authorized by USFWS in 2018
Source: 50 CFR §22.260 (2024); USFWS Eagle Incidental Take Permits for Power Lines. fws.gov →
🗂️ Where to Find Specific Unfixed Pole Location Data
- FOIA Request to USFWS Region 6 (Denver) — Utility Avian Protection Plans list specific problem poles and retrofit status by service area; mortality reports by utility are on file
- APLIC Bird Mortality Tracking System — free software used by utilities to log problem pole locations; not publicly accessible but FOIA-requestable from USFWS
- DOJ Press Releases — all criminal prosecutions: justice.gov/archive/opa
- USFWS Eagle Resource Equivalency Analyses — documents compensatory mitigation credits, including specific poles and utilities involved in ILF transactions
- State Wildlife Agency Records — Wyoming Game & Fish, Montana FWP, Idaho F&G, Colorado Parks & Wildlife all maintain raptor mortality databases
- Eagle ILF Program — eaglemitigation.com — lists utilities currently enrolled and purchasing mitigation credits (implies unfixed poles)
☠️ Poisoning — Lead Ammunition & Rodenticides
📐 Primary Sources — Lead Poisoning Section
Katzner, T.E., et al. (2022). "Demographic implications of lead poisoning for eagles across North America." Science 375(6582):779–782. DOI: 10.1126/science.abj3068 — first continental-scale study; 1,210 eagles, 38 states, 8 years. Peer-Reviewed
Mojica, E.K., et al. (2017). "Characterizing Golden Eagle Risk to Lead and Anticoagulant Rodenticide Exposure: A Review." Journal of Raptor Research 51(3). View Study — exposure pathways, blood lead thresholds, anticoagulant rodenticide data. Peer-Reviewed
USGS Open File Report 2023-1016. "Bald eagle and golden eagle mortality and exposure to lead, mercury, and anticoagulant rodenticides in eight western and midwestern states, 2014–17." pubs.usgs.gov — 314 eagles necropsied; cause-of-death breakdown for golden eagles specifically. Gov't / USGS
Lanzone, M., et al. (2017). "Sublethal Lead Exposure Alters Movement Behavior in Free-Ranging Golden Eagles." Environmental Science & Technology 51(10). DOI: 10.1021/acs.est.6b06024 — GPS tracking shows measurable flight impairment at sublethal blood lead levels. Peer-Reviewed
Scale of the Problem Katzner 2022 Millsap 2022
- ~400–427 golden eagles killed annually by poisoning (Millsap et al. 2022, modeled estimate; represents ~13% of post-first-year deaths)
- 46% of golden eagles show chronic lead poisoning — long-term accumulation in bone detected across 1,210 sampled eagles in 38 states (Katzner et al. 2022, Science)
- 9% show acute lead poisoning — blood concentrations high enough to potentially cause death
- Lead accumulates in bone with age — chronic exposure rates increase the older the eagle
- Golden eagle population growth suppressed by ~0.8% annually from lead alone (Katzner 2022) — on a population of ~30,000, that's ~240 birds of reproductive potential lost per year
- One fragment of lead the size of a grain of rice is sufficient to kill an eagle
🔫 Source 1 — Lead Ammunition (Primary Pathway)
How It Works: The Gut Pile & Carcass Chain
A single rifle bullet produces approximately 235 fragments in the carcass and 170 fragments in the viscera of the target animal (Mojica et al. 2017). When hunters field-dress game and leave the gut pile, or when carcasses from predator control remain in the field, eagles and other scavengers ingest these fragments directly. Copper alternatives mushroom or "petal" on impact and remain nearly intact — lead rounds shatter.
- Seasonal spike — winter and fall hunting season: Acute poisoning is most common in winter months when eagles scavenge more heavily. Blood lead concentrations in eagles increased 1.8× during fall big-game hunting season in southern California (Mojica 2017). Minnesota bald eagles showed 7.6-fold increases during white-tailed deer season.
- Prairie dogs & ground squirrels (year-round): Shot rodents contain 39–228 mg of lead per carcass; 7–47% of all carcasses in studies had sufficient lead mass to be lethal to raptors. Recreational shooting of these animals is a major year-round exposure pathway for western golden eagles (Thunder Basin National Grassland, WY; documented by USFWS).
- Predator control carcasses: Coyote control programs that leave shot animals on the landscape provide additional lead-laden scavenging opportunities.
🧠 Sublethal Effects — The Hidden Mortality Multiplier
Lead poisoning doesn't just kill directly — it impairs eagles in ways that increase death from other causes (Lanzone et al. 2017, Env. Science & Technology):
- At 25 ppb blood lead: measurable changes in movement behavior detected via GPS tracking
- At ~43 ppb blood lead (inflection point): flight height reduced by 20%
- At highest measured concentrations: flight height reduced by 50%
- Physiological effects: anemia, immunosuppression, liver/kidney damage, central and peripheral nervous system disruption
- Synergistic risk: Lead-impaired flight coordination directly increases probability of collision with vehicles, power lines, and wind turbines — meaning lead poisoning amplifies every other mortality category
🩸 Source 2 — Anticoagulant Rodenticides (Secondary Pathway)
What the USGS 8-State Necropsy Study Found (2023)
USGS Open File Report 2023-1016 necropsied 142 golden eagles from ND, SD, MT, WY, CO, UT, NE, and KS (2014–2017):
- Golden eagle causes of death: Trauma 58%, Electrocution 27%, Lead toxicity 7%, Disease 3%, Other 4%
- 39% of golden eagles tested positive for brodifacoum (second-generation anticoagulant rodenticide) in liver tissue
- 4.5% of golden eagles had severe clinical lead poisoning (>10 mg/kg wet weight liver)
- Lead concentration highest in North Dakota, South Dakota, and Nebraska
- AR-caused death directly attributed in only 1 of 142 golden eagles — but presence at 39% suggests ongoing sublethal exposure across the range
Anticoagulant Rodenticide Exposure — Broader Literature (Mojica et al. 2017 Review) Mojica 2017
- Across 6 peer-reviewed studies examining 48 golden eagles: 67% (32 of 48) showed AR exposure; at least 17% exceeded toxic thresholds (0.1 ppm wet weight in liver)
- Compounds detected: brodifacoum, bromadiolone, difethialone, flocoumafen — second-generation ARs predominate
- Most AR-exposed eagles recovered near urbanized areas, not typical remote golden eagle habitat — suggests suburban/agricultural rodent control as the exposure vector
- AR exposure causes weakness, behavioral impairment, and increased coagulation time — increasing collision risk even if not directly lethal
- Major data gap: Only 48 golden eagles assessed for AR exposure in all published literature as of 2017 — this is vastly understudied relative to the scale of AR use in the West
💡 The Fixable Problem — Non-Lead Ammunition
Lead poisoning is the only major eagle mortality cause that could be completely eliminated by a single policy change — unlike turbines, collisions, and electrocution which require infrastructure retrofits.
- Solid copper bullets "petal" on impact rather than fragmenting; retain nearly all mass; are non-toxic if ingested
- Copper bullets are equally accurate and effective for big-game hunting
- Non-lead options now cover every hunting use case — solid copper bullets for centerfire rifles, plus bismuth, tungsten, and steel shot for shotguns — and modern non-lead loads are widely reported to match lead-core ammunition for accuracy and field performance
- California is the only state that bans lead ammunition for hunting big game (statewide)
- Lead ammunition for waterfowl has been federally banned since 1991 — with no meaningful decline in hunting success
- Voluntary non-lead programs (New York, Minnesota, others) show adoption is possible without mandates
- Cornell University study (2024): bald eagles face highest lead risk of all deer-season scavengers in NY — reinforcing ammunition as the primary driver
🤝 Featured Partner Resource
North American Lead-Free Partnership
A hunter-led conservation coalition working to keep lead from hunting ammunition out of the wildlife food chain — the same gut-pile and carcass pathway that exposes scavenging golden eagles. Rather than relying on mandates, the Partnership backs hunters who voluntarily choose non-lead ammunition, framing the switch as a continuation of the hunting community's long conservation legacy.
- A non-lead ammunition finder to help hunters locate — and afford — copper and other non-lead loads
- Plain-language education and data on how lead reaches eagles and other scavengers
- Voluntary, incentive-based programs and a partner network spanning wildlife agencies, conservation groups, and the ammunition industry
- Hunter stories and podcasts that make the case from inside the hunting community
Visit the North American Lead-Free Partnership →
leadfreepartnership.org · external site, opens in a new tab
⚠️ Blood Lead Concentration Reference Thresholds (Mojica et al. 2017)
🩸 Show blood lead threshold reference table
| Blood Lead Level |
Classification |
Observed Effects |
| <0.20 ppm |
Background |
No clinical effects |
| 0.21–0.50 ppm |
Elevated exposure |
Measurable movement behavior changes (Lanzone 2017) |
| 0.51–1.00 ppm |
Chronic exposure |
Anemia, immunosuppression, 20–50% flight height reduction |
| >1.01 ppm (or >10 mg/kg liver) |
Hazardous / Clinical |
Acute toxicity, death possible; 4.5% of golden eagles in USGS 8-state study exceeded this (2014–17) |
65% of breeding adult golden eagles in Columbia Basin (WA) exceeded background levels; 24% showed chronic exposure (Mojica 2017).
Millsap et al. (2022) Survival Rate Findings: Peer-Reviewed
- First-year birds: ~70% annual survival rate (most vulnerable age class)
- Adult eagles: ~90% annual survival rate
- Young eagles face nearly 3× higher mortality than adults
- Cumulative effect: Only ~30% of first-year eagles survive to adulthood
- These are posterior median estimates from Bayesian analysis; consult paper for 90% credible intervals.
The Bottom Line: Population Sustainability
🎯 What Millsap's Research Means for Policy Millsap 2022
Based on survival rates and causes of death, Millsap et al. (2022) estimate the western golden eagle population can sustain an annual loss of approximately 2,227 birds (90% credible interval: 708–4,182) while maintaining population stability. This number directly informs federal "incidental take" permits for wind farms, power lines, and other projects. Any management strategy must account for the fact that most deaths are human-caused and concentrated in specific locations.
Source: Millsap, B.A., et al. (2022). Ecological Applications, 32(3). Peer-Reviewed
Key Research Publications on Causes of Death
Eagle In-Lieu Fee (ILF) Program — Utilities — Eagle Electrocution Solutions / USFWS-authorized. First mitigation credit program under BGEA (2018). Lists enrolled utilities purchasing credits in lieu of direct pole fixes.
Industry Program
North American Lead-Free Partnership — Hunter-led conservation coalition promoting voluntary non-lead ammunition use; offers a non-lead ammunition finder, hunter education resources, and incentive-based programs.
Conservation Organization