Identification of Bald and Golden Eagle Feathers

1. What they did

Wildlife law enforcement officers often come across feathers that might be from eagles, either loose or worked into crafted items such as headdresses and dance fans. Identifying them can be hard: bald and golden eagle feathers are similar in size, both species change a great deal in appearance as they age, and feathers of young eagles are especially variable. Feathers of other large birds, such as turkeys, geese and vultures, are also used in place of eagle feathers.

This guide from the U.S. Fish and Wildlife Service’s National Fish and Wildlife Forensics Laboratory sets out how to tell the two eagles apart, and how to rule out other birds. It focuses on flight feathers (the large wing and tail feathers), because these are the ones most often used in crafted items. It uses 25 figures, mostly scans from the Feather Atlas of North American Birds, and ends with a one-page summary table. The aim is identifying the species, not the age of the bird.

2. What they found

Bald eagle versus golden eagle

• Adult bald eagle: tail feathers are pure white; wing feathers are plain dark grey or grey-brown, sometimes with a very small whitish patch at the base. They never show marbling.
• Adult golden eagle: most wing and tail feathers show “marbling”, curved or irregular pale patches, spots and bars on chocolate brown. Marbling is never seen on bald eagle feathers. The outer three to five primaries lack marbling and usually cannot be told from bald eagle feathers without reference specimens.
• Subadult bald eagle: probably the hardest feathers to identify. They look mottled or “mud-spattered”, with blotched and speckled white areas, often in the middle or near the tip, surrounded by dark vane. Any pure white patch at the base is much smaller than on a young golden eagle.
• Subadult golden eagle: a large, mostly pure white patch extends up from the base of the feather, with a dark tip, and often the beginnings of marbling. Tail feathers of one-year-olds, with white bases and dark tips, are the most prized eagle feathers for headdresses.
• Both species usually reach full adult plumage by their fifth year.

Ruling out other birds

• Shaft: eagle and other raptor shafts are plain on top with only a narrow V-shaped groove underneath. Turkeys and other gamebirds have fine parallel lines on top and a broad U-shaped groove underneath.
• Size: eagle flight feathers are almost always 26 cm (10 inches) or longer, and even the shortest secondaries are at least 20 cm (8 inches). Anything shorter is not an eagle flight feather.
• Hawks: all North American hawks, and the osprey, are much smaller. The rough-legged hawk is the one hawk used to imitate eagle feathers: its tail feathers can look like a young golden eagle’s but are 22 to 25 cm long, against 30 to 38 cm for golden eagle.
• Condors: far larger than eagles (primaries 43 to 70 cm against 32 to 54 cm for eagles) and never marbled, mottled or white-based.
• Black and turkey vultures: dark, unpatterned feathers like adult bald eagle, but smaller, with paler undervanes and pale shafts that contrast with the vanes.
• Turkeys: wild turkey feathers are strongly barred. Some domestic breeds have marbling-like patterns, and dyed white domestic turkey feathers are by far the most common fake eagle feathers. The dye looks unnaturally even, the feathers are arched (cambered), and the shafts show the gamebird lines and grooves.
• Geese and swans: waterfowl primaries have a shiny “tegmen” layer on the undersides, never seen on eagles. Their secondaries and tail feathers are too small.
• Great blue heron: paler, slate-blue, smaller feathers, without the long “fingers” on the outer primaries.
• Common raven: truly black feathers, often with a blue sheen, and smaller and more slender. Eagle feathers are never truly black.

3. What they concluded

The summary table gives the key rules:

• A feather cannot be from a bald eagle if it shows marbling (adult golden eagle) or has a large pure white base and dark tip (subadult golden eagle).
• A feather cannot be from a golden eagle if it is pure white (adult bald eagle tail feather) or has white areas mottled with brown and surrounded by dark areas (subadult bald eagle).
• A feather cannot be from an eagle if it has tegmen (waterfowl), fine lines along the top of the shaft or a broad U-shaped groove underneath (most likely gamebird), or a white shaft contrasting strongly with darker vanes (most likely vulture).
• If still uncertain, compare sizes with the Feather Atlas. Suspected eagle feathers seized at ports of entry should go to the Forensics Laboratory, because close relatives of both eagles live outside North America.

4. How tracking was or was not used

No field tracking. The guide is about identifying one kind of sign, feathers, by their pattern, colour, shape, shaft structure and size, using reference scans.

6. Other technologies, skills or innovations

• The Feather Atlas of North American Birds (an online collection of feather scans with measurements and a glossary) as the reference for comparison.
• Close examination of the shaft surfaces and the undersides of the vanes (tegmen), and viewing feathers edge-on to see camber.