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Current Threats Facing Bald and Golden Eagles

Title

From Mercury and Lead to Wind Turbines and Habitat LossA synthesis of current literature and research

David Kramar

Banding and Capture

• Tremendous differences between trapping/banding

juveniles as opposed to adults.

• Juveniles must be acquired from the nest.

• Adults must be caught via nets, traps, etc.

• Major difference: Climbing versus sitting in a blind

Morphometrics • Weight

• Wing Chord

• Tail Length

• Culmen (with and without cere, depth)

• Halux length

• Tarsus length, width

• Crop (full, ½ full, empty)

Eaglet Sampling

� Targeted major rivers in the state stratifying

based on salinity.

� Sampled eaglets confirmed 4-8 weeks

� Traditional lanyard & spike methods

�Traditional rope climbing methods

Blood Samples Collected using 21-25 gauge butterfly needles and Vacutainers, or a straight draw.

Drawn from the caudial tibial vein or the brachial vein.

3 contour feathers collected

Morphometrics

Eaglet Hg Sampling

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Trapped using bait and rocket/cannon nets.

Collection of blood and feather follows that of

the juveniles.

Adults much more dangerous to handle/band.

Precautions need to be taken to insure the safety of the bird as well as the biologists.

Adult Sampling Adult Sampling

Adult Sampling Adult Sampling

Overview of Threats

• Mercury (Hg) and Methyl-Mercury (CH3Hg+)

• Lead (Pb)

• Incidental Trapping/Poisoning

• Electrocution

• Air Strikes

• Turbine Collision

• Habitat Loss

Mercury Overview

• Methylmercury is one of the more toxic substances environmentally available to wildlife and humans

• It is a toxin that primarily targets the brain

• There is a mix of anthropogenic and natural Hg sources

• Most widespread/large-scale ecological Hg problems have an atmospheric source

• Atmospheric sources are local, regional, continental, and global. Significant global increases are in process.

• Rate of atmospheric Hg deposition on the East Coast is high enough to cause risk

• Multiple factors are responsible for the production and availability of methylmercury

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Mercury Overview

Accumulation in birds is strongly associated with diet.

• For example: Bald Eagles will likely exhibit higher levels than Golden Eagles.

• Increasing trend from herbivore – piscivore

Current levels of MeHg availability exceed historical levels and ecological impacts are currently being detected across the east coast

Lakes are highest risk habitats, but ecological risks are evident in other areas such as urban estuaries and wetland and high altitude conifers;

Trophic level by foraging guild in waterfowl

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0.20

0.40

0.60

0.80

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1.20

1.40

Herbivore (n=10) Omnivore (n=45) Insectivore (n=39) Piscivore (n=51)

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Hg (

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Mercury Overview

• Strongly Associated with freshwater environments

• By-product of sulfate reducing bacteria

• Methylation generally occurs in the top few inches of sediment

• Hg bonds readily with DOC, particularly that of high molecular weight

• Presence of carbon, hydrogen, and sulfur increase the likelihood of methylation (coined the Biogeochemical Axis of Evil)

• Not generally a concern in saline environments

Virginia

� Little work has been conducted when compared to other states.

� Only one previous study that looked specifically at bald eagles.

� Collected non-viable eggs somewhat randomly

� Exhibits a large bald eagle population

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Known Inland Nest Locations Data of Significance

Land Cover

Sediment Mercury

Fish Mercury

Locations of Point Sources

Coastal vs Inland

Results

Location Blood Hg mg/kg Feather Hg mg/kg Talon Hg mg/kg

Coastal 0.0513 2.1007 2.5503

Inland 0.2717 4.4972 4.3669

Mean Blood, feather, and talon mercury levels for coastal and inland nests

Coastal vs. Inland Nests

Inland nests exhibited statistically higher concentrations of Hg than those located in the coastal plain.

Sediment Hg and Eagle Hg

As expected, there is a positive relationship between sediment Hg levels and concentrations of Hg found in juvenile bald eagles.

Measured Mercury Levels

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Estimated Mercury Levels Residuals

Inland Surveys (VaDGIF)

� Aerial surveys of inland Virginia had never been conducted

� Isolated many new nests and confirmed the presence/activity of previously known nests.

� Spacing along major rivers is between 12-20 miles apart, but fairly consistent in that spacing.

� Prey Availability??

Results – Preliminary Model

Used Generalized Linear Modeling (GLM) techniques to analyze land cover relationships

Results indicated a relationship between pasture and commercial land as well as coastal/inland.

Resulting model output indicated a good fit.

Lead and EaglesWhen ingested in large enough quantities, lead has

detrimental effects on the nervous and reproductive systems of mammals and birds• Eagles frequently scavenge carcasses of deer, pheasants and other wildlife that may harbor lead or lead fragments

• Live prey impaired by lead ingestion, such as waterfowl, become easy targets for eagles• Eagles with lead poisoning may exhibit loss of balance, gasping, tremors and impaired ability to fly• Emaciation follows and death can occur within 2 to 3

weeks after lead ingestion (could pick up during migration)

Sources of LeadLead fragments in prey hunted by humans pose a continuing

Deadly threat to raptors, including golden eagles. (Stauber et al. 2010)

Before 1980's lead ingestion was main cause of death of California condors (Wiemeyer et al. 1988)

36% of golden eagles captured in southern California between 1985-1986 had been exposed to lead (Hunt et al. 2009)

Large amounts of lead showed in blood tests of bald and

golden eagles in Yellowstone Nat. Park during hunting season. (Bedrosian & Craighead 2009)

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Sources of LeadIn a study of cases between 1991 and 2008, 62% of golden

eagles admitted to a rehabilitation center in Pacific Northwest of U.S. had toxic blood concentrations of lead (Stauber et al. 2010)

Lead poisoning and heavy metal exposure documented in

wild golden eagles from Austria, Germany and Switzerland 2000-2001 (Kenntner et al. 2007)

Sources of Lead

Buckshot in bald eagle stomach, photo courtesy Wildlife Center of Virginia.

Sources of Lead

Lead-poisoned bald eagle photo courtesy The Raptor Center, University of Minnesota.

Incidental Trapping/Poisoning

� Occurs when an eagle is trapped accidentally while

trapping a different species.

� Two incidents of a golden eagle incidentally trapped in Virginia last year. One was able to be released.

� In many cases these incidents are likely not reported.

� Occurs throughout the US and Canada.

� Likely more widespread than we know.

Incidental Trapping

Image credit: Raptor Center

Incidental Trapping

Image credit: Virginia Tech

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Electrocution

� Occurs when an eagle is perched and accidentally touches

both a live wire and the ground.

� Occurs when an eagle accidentally flies into a line during lowvisibility days.

� Are preventable to an extent

�Among the top five causes of deaths to eagles.

� Study by Watts et al. In Virginia

Electrocution

Image credit: Anonymous

Electrocution

Second oldest bald eagle documented in Alaska. Photo: Robin Corcoran

Airstrikes

� Currently a large issue both in Virginia as well as the US.

� Norfolk Botanical Gardens Female

� Between 2002 – 2011 there are nine reports of bald eagle strikes by planes in Virginia (FAA). Five at Newport News, Four

at Norfolk.

� Many reports throughout the United States

Wind Energy and Eagles

Title

Altamont Pass

� ~67 Goldens struck each year..

� Scores of other birds and bats.

� Large nesting golden eagle population

5000 Older turbines; This is always the “example”

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Foote Creek Rim

� Located in Wyoming

� Developers moved turbine locations back

� Fewer collisions due to appropriate planning

� Newer versus older turbines

What about Appalachia?

� Several areas are being evaluated for the development of turbines.

� Research by Trish Miller, Mike Lanzone, and Todd Katzner suggest that development can be done to accommodate both wind power and migrating raptors.

� Eastern golden eagles use a fairly small corridor.

� Use high resolution GPS telemetry units.

What about Appalachia?

� No known mortalities in Eastern US.

� EGEWG working to better understand the small eastern population.

� No known nesting pairs in the US, east of the Mississippi since the 1990's.

� Greatest numbers in the winter are found in the Appalachians of PA, WV, and Va. (Miller and Katzner, Unpublished data)

The GPS Units

Satellite vs. Cellular

� Pros and Cons

The Field Sites

� Highland County, Virginia

� Clinch Mountain Wildlife Management Area

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The Data

� Cellular based data are dumped whenever the GPS unit acquires a cellular signal.

� Points are collected every 15 minutes until a geo-fence is crossed.

� After passing the geo-fence, data are collected every 30 seconds.

� Fences are set in areas known for potential wind energy sites and major metropolitan areas

The Data

� Integrated with Google Earth.

� High Resolution

� Down-loadable data

The Data Highland County

Highland County Clinch Mountain

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Clinch Mountain Clinch Mountain

All Tracks on One Map

Map provided by:the National Aviary and Carnegie Museum of Natural History

Habitat Loss

Likely one of the largest factors affecting the future ofbald and golden eagles

Historically, as human population expands and grows, Eagle populations decline.

Most destructive human activity for bald eagles is the Development of waterfront property.

Cutting of old growth forests

Habitat Management Plans

Other Threats

DDT – While banned in the US, it is still used in Mexico and other countries. Initially one of the reasons that Bald eagle populations declined.

Mortality rate – Only a fraction of individuals fledged Survive the first year. Often they die as a result of threats Mentioned earlier.

Poaching – Unfortunately, this still happens. As recently as 1989, over 20% of eagle fatalities were from being shot.

Secondary poisoning – poisoning from tainted bait used to kill Nuisance species.

Acknowledgements

Special Thanks to:

Michael Lanzone and Trish Miller (Carnegie Museum of Natural History)

Dr. Todd Katzner (National Aviary)

Jeff Cooper (Va. Dept of Game and Inland Fisheries)

Highland County Birding Club

Clinch Mountain Wildlife Management Area Staff

USFWS, VDGIF, and many Others for the Opportunity to Work on This and other Projects!

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Questions?