# Identifying Bald Versus Golden Eagle Bones: A Primer for Wildlife Biologists and Law Enforcement Officers > When all that is left of an eagle is a pile of bones, can you tell a bald eagle from a golden eagle? A U.S. Fish and Wildlife Service forensic scientist found simple shape features on eight bones, from a “window” in the skull to a notch at the top of the lower leg bone. Using only his annotated photographs, volunteers with no experience of eagle bones got 93 to 100% of identifications right. Summary by Kersey Lawrence, Original Wisdom. Updated 9 November 2026. Page: https://www.originalwisdom.com/tracking-literature/2017-trail-identifying-bald-versus-golden/ ## Citation and access - **Authors:** Pepper W. Trail - **Year published:** 2017 - **Journal or source:** Journal of Fish and Wildlife Management - **Full citation:** Trail, P. W. 2017. Identifying bald versus golden eagle bones: a primer for wildlife biologists and law enforcement officers. Journal of Fish and Wildlife Management 8(2): 596–610. - **DOI:** 10.3996/042017-JFWM-035 - **Access status:** Hosted: U.S. government work, not subject to copyright in the United States - **PDF:** https://www.originalwisdom.com/wp-content/uploads/2026/11/2017_Trail_identifying-bald-versus-golden-eagle-bones-a-primer-for-wildlife-biologists-and-law-enforcement-officers.pdf ## Tags - **Species:** Birds > Bald eagle; Birds > Golden eagle - **Region:** North America > United States - **Tracking:** Bones; Tracking; Tracks and signs identification - **Methods and technology:** Descriptive statistics; Observer reliability - **Data type:** Existing data; New field data; Protocol or guidelines - **Observer qualification:** Not needed - **Discipline:** Forensics; Wildlife tracking - **Year published:** 2017 ## Detailed keywords - **Species:** Studied: bald eagle (Haliaeetus leucocephalus) and golden eagle (Aquila chrysaetos). Bone lengths also measured for comparison: osprey (Pandion haliaetus), red-tailed hawk (Buteo jamaicensis), ferruginous hawk (Buteo regalis), northern goshawk (Accipiter gentilis), turkey vulture (Cathartes aura) and great horned owl (Bubo virginianus). Large non-raptor birds whose limb bones could be confused with eagle bones (lengths taken from Gilbert et al. 1981): tundra swan (Cygnus columbianus), Canada goose (Branta canadensis), wild turkey (Meleagris gallopavo), American white pelican (Pelecanus erythrorhynchos), great blue heron (Ardea herodias), whooping crane (Grus americana) and sandhill crane (Antigone canadensis). Mentioned: California condor (Gymnogyps californianus); swans, turkeys, pelicans and cranes in general. Humans: six volunteers tested the guide. - **Location and habitat:** Skeleton reference collection of the National Fish and Wildlife Forensics Laboratory (NFWFL), Ashland, Oregon, United States. The guide applies only to remains known to be from North America; eagles of the same genera from elsewhere are not covered. Field settings mentioned: avian mortality surveys at wind energy facilities and along power lines, and wildlife crime investigations. - **Topics:** osteology (bird bones); species identification of skeletal remains; shape-based diagnostic characters; skull (interorbital septum, postorbital process, beak), sternum, pelvis (synsacrum), coracoid, humerus, ulna, tibiotarsus and tarsometatarsus; bones too similar to use (furcula, scapula, radius, carpometacarpus, femur); size overlap, sexual dimorphism and geographic variation; ruling out other raptors and large non-raptor birds; bird mortality at wind farms and power lines; wildlife law enforcement and forensics; eagle bones in crafted items such as Native American style bone flutes; Migratory Bird Treaty Act and Bald and Golden Eagle Protection Act; blind identification tests with untrained volunteers. - **Statistics or models:** Descriptive statistics only: bone lengths measured with digital calipers (means, standard deviations and ranges), and percentage error in the volunteer identification tests. Small inconsistencies: the text says seven of eight elements were identified correctly in 95% of comparisons with only the ulna below (93%), but Table 3 gives the tibiotarsus 8 errors in 150 (about 94.7% correct). The Methods give sample sizes of 10 to 24 individuals per species, while Table 1 gives 11 to 19 (bald) and 12 to 24 (golden). The citation printed on the paper gives pages 595 to 609; the journal pages are 596 to 610. The caption of Table 2 says photographs were taken at the NFWFL, although its data come from Gilbert et al. (1981). - **Data type:** New field data: bones examined, photographed and measured in the NFWFL collection in 2016 and 2017, and blind identification tests with six volunteers. Existing data: lengths of large non-raptor bird bones from Gilbert et al. (1981). Published as an identification guide (a “Note”). ## Synopsis ### 1. What they did Bald eagles and golden eagles are North America’s largest birds of prey apart from the California condor, and both are protected by federal law in the United States. Their remains turn up in bird mortality surveys at wind farms and power lines, and in wildlife crime investigations. With feathers, the two species can almost always be told apart. But sometimes only bones are left after decomposition and exposure, and eagle bones are also found in crafted items with no feathers attached. Until this paper there was no guide to telling the two species’ bones apart that non-specialists could use. The author, of the U.S. Fish and Wildlife Service National Fish and Wildlife Forensics Laboratory (NFWFL), worked as follows: - Comparing bones. He examined all the major bones of bald and golden eagles in the laboratory’s reference collection (10 to 24 individuals of each species, depending on the bone). - Choosing useful bones. Five bones (wishbone or furcula, scapula, radius, carpometacarpus and femur) were dropped because they look too alike. Eight bones showed reliable shape differences: skull, sternum, pelvis, coracoid, humerus, ulna, tibiotarsus and tarsometatarsus. - Making a photo guide. He photographed an example of each bone from both species and marked the features that tell them apart. - Testing the guide. Six volunteers, ranging from no biology training to a PhD in mammalogy but none with experience of eagle bones, were given mixed, unmarked bones of both species and asked to identify them using only the annotated photographs. Features they found hard to judge were dropped. - Measuring size. He measured the total length of the eight bones in both eagles and six other large North American raptors, and compared them with published lengths for large non-raptor birds. ### 2. What they found Size - Size alone almost always separates eagle bones from those of other North American raptors. - But bald and golden eagle bones overlap widely in size, made worse by differences between the sexes and between regions, so the two eagles should not be told apart by measurements. - Several large non-raptor birds (swans, Canada goose, wild turkey, pelican, great blue heron, cranes) have limb bones large enough to be confused with eagle bones. Skulls, breastbones and pelves of these birds look clearly different from an eagle’s. If only limb bones of an unknown large bird are present, the author advises not to attempt identification without a reference collection. Shape features that tell the two eagles apart - Skull, side view: bald eagles have a solid plate of bone between the eyes; golden eagles have an obvious “window” in it. Bald eagle beaks are more massive and often yellow, golden eagle beaks always dark, but beaks should not be relied on alone (young bald eagles have dark beaks, and beaks found in the field are often damaged). - Skull, back view: the bony projections behind the eyes are slender and pointed in bald eagles and broad plates in golden eagles. - Sternum (breastbone): long with parallel sides in bald eagles; compact and broadening towards the rear in golden eagles, often with small holes at the rear corners, which are never seen in bald eagles. - Pelvis: the hip crest is a smooth curve in bald eagles and angled and flared in golden eagles. - Coracoid: golden eagles have a raised “mushroom cap” of bone near the shoulder end; bald eagles have a smooth transition. - Humerus (upper wing bone): the hollow in the head of the bone is large and round in bald eagles, smaller and more pointed in golden eagles. - Ulna (lower wing bone): the ridge at the wrist end is rounded and almost C shaped in bald eagles, elongated and D shaped in golden eagles. This is the hardest bone to identify. - Tibiotarsus (middle leg bone): a long slender curve on the side crest in bald eagles, broader in golden eagles. - Tarsometatarsus (lower leg bone): golden eagles have an obvious deep notch at the top of the bone; bald eagles do not. This bone alone can give a reliable identification. The volunteer tests - Errors ranged from 0% (skull, side view) to 7% (ulna, 9 wrong out of 132). - Each volunteer was 95 to 100% correct across all bones combined. ### 3. What they concluded - If an intact skull or the lower leg bones (tarsometatarsi) are present, identifying the species should be straightforward and unequivocal. - Even without them, untrained volunteers using the photographs identified the pelvis, sternum, coracoid, humerus and tibiotarsus correctly 95% of the time, and the ulna 93% of the time. - In the field, remains usually include several bones, and identification should be based on all the informative bones together. This should allow the two eagles to be told apart in almost every case. - The ulna should not be used alone when other bones are available. It is included because ulnas are the bones most often used to make Native American style bone flutes, so they are often seen in wildlife crime cases. - The author encourages wildlife biologists and enforcement officers to carry printouts of the figures as a field reference. ### 4. How tracking was or was not used No tracking in the field. The paper is about one kind of sign: identifying the species from bones left after death. The guide assumes enough remains are present to show they are an eagle (for example, part of a skull or a foot with large talons). ### 5. Tracker or observer certification The identification guide was tested by six volunteers, named in the acknowledgments, with varying backgrounds in biology and no previous experience with eagle bones. They had no certification; their accuracy with the guide was measured in blind tests. Two of the volunteers also measured the bones. ### 6. Other technologies, skills or innovations - Annotated photographs of each bone, designed for use in the field and at places without a reference collection. - Digital calipers for bone lengths. - Supplementary table of bone measurements for large raptors in the NFWFL collection. ### 7. Implications for conservation (from the paper) - Eagle deaths at wind energy facilities are a growing concern, and these facilities are spreading into areas used by golden eagles. Reliable species identification is essential for the mortality surveys run at wind farms and along power lines. - Golden eagle populations in the United States are stable or slowly declining, and most recorded deaths are caused by people (shooting, electrocution and lead poisoning). - The guide supports wildlife law enforcement, where eagle remains and crafted items are examined as evidence. ### 8. Implications for tracking (Original Wisdom's observations) _These are Original Wisdom's observations, not the authors'._ - Bones are often what remains at a kill site, a carcass or a scavenged site. This guide shows how a few clear shape features, checked against good photographs, can let people with no specialist training identify bones with high accuracy. - The way the guide was built is a useful model: features that volunteers could not judge reliably were dropped, and only those that tested well were kept. ## Cite this summary Lawrence, K. 2026. Summary of: Identifying Bald Versus Golden Eagle Bones: A Primer for Wildlife Biologists and Law Enforcement Officers (Trail, 2017). Original Wisdom, Tracking Literature. https://www.originalwisdom.com/tracking-literature/2017-trail-identifying-bald-versus-golden/