Identification of Eagle Feathers and Feet

1. What they did

Wildlife law enforcement officers are often asked to examine crafted items, such as headdresses, dream catchers and dance fans, that may contain 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 North American eagles apart from their feathers, for both adults and immature birds.
• Rule out look-alike feathers from geese and swans, turkeys and peafowl, vultures, and other birds of prey.
• Tell bald and golden eagle feet apart, since lower legs and feet also turn up in wildlife crime cases.

It explains the parts of a feather and the different flight feathers, then gives the key features for each case, with a summary table and 15 photographs.

2. What they found

Golden eagle

• Adults are brown all over. Most wing and tail feathers show “marbling”: paler bars, curved or oval marks and small patches on chocolate-brown. Marbling is never seen on bald eagle feathers.
• The outer 3 or 4 primaries (the notched, finger-tipped wing feathers) are very dark with no marbling, and usually cannot be told from a bald eagle’s without reference specimens.
• Immature birds have large white bases on their flight feathers, with dark tips. The white patch is mostly pure white, rises from the base as a single area, and may show traces of marbling at its edge. Golden eagles reach adult plumage at 3 to 4 years. These immature feathers are the most prized for crafted items.

Bald eagle

• Adult tail feathers are pure white. Adult wing feathers are plain dark gray or gray-brown, sometimes with a tiny whitish patch at the base, never patterned.
• Immature plumage is more variable and takes about five years to reach adult plumage. Immature feathers look “mud-spattered”: the white is speckled and blotched and often sits in an isolated patch surrounded by dark. These are probably the most confusing feathers to identify.

Ruling out other birds

• Geese and swans: a waxy-looking strip (the “tegmen”) along the shaft on the underside of the primaries. Never seen in eagles.
• Turkeys and peafowl: fine parallel lines inside the upper side of the shaft, and a broad U-shaped groove under the shaft. Eagles show no lines and only a fine line or narrow groove underneath. White turkey feathers are often dyed brown at the tip to look like immature golden eagle feathers.
• Vultures: white shafts that stand out against grayish vanes (on the underside in turkey vultures, both sides in black vultures). Eagle shafts do not contrast like this.
• Other birds of prey: size is usually enough. Eagle primaries are 16 to 22 inches long and secondaries and tail feathers 10 to 14 inches. Hawk, falcon and owl primaries are under 14 inches. The osprey comes closest in size but has strong brown and white barring.

Feet

• Golden eagles have feathers down to the base of the toes; bald eagles have bare, scaly lower legs, orange-yellow when fresh or frozen, fading to brownish when dried.
• The central toe of both eagles is at least 2 inches long without the talon; in osprey and ferruginous hawk it is at most 1.5 inches.

3. What they concluded

• Eagle feathers can be identified by a short set of features, summarized in Table 1. A feather cannot be from an eagle if it has a tegmen layer, fine lines along the upper shaft, a broad U-shaped groove under the shaft, or a white shaft contrasting with darker vanes.
• A feather cannot be from a bald eagle if it shows marbling or a large pure-white base with a dark tip (golden eagle). It cannot be from a golden eagle if it is pure white or has speckled white areas surrounded by dark (bald eagle).
• Feet are much easier to identify than feathers.

4. How tracking was or was not used

The guide is about identifying animal remains, a form of signs identification, rather than tracking in the field. It teaches how to read feathers and feet: pattern, colour, shaft structure and size.

6. Other technologies, skills or innovations

• A magnifying lens makes the shaft lines of gamebirds easier to see, although they can usually be seen with the naked eye.
• Reference specimens are needed to separate the dark outer primaries of the two eagles.
• Photographs are shown with a scale bar.