Axillaries: feathers in the axilla ("armpit") of the bird. In some birds, such as Bald Eagle, these are large enough to merit illustration in the Feather Atlas
Barb: an individual strand of feather
material (keratin), extending laterally from the rachis.
Barbule: a lateral branch of a feather barb
Calamus: the hollow inner portion of the
feather shaft that lacks barbs and attaches to the skin. Sometimes
called the quill.
Contour Feathers: the feathers forming the
bird's outer body covering, including the flight feathers
and the overlapping body feathers that produce the bird's
smooth aerodynamic shape.
Coverts: the contour feathers that cover the bases of the flight feathers. Those on the upper (dorsal) surface of the body are called upper wing and upper tail coverts; those on the under (ventral) surface are called under wing and under tail coverts. In some birds, such as eagles, these are large enough to merit illustration in the Feather Atlas.
Dorsal: the upper surface of the body, or of any body part oriented in a normal horizontal position. Most scans in the Feather Atlas illustrate the feathers in dorsal view, showing the upper surface of the feathers.
Emargination: a distinct narrowing in the
anterior vane of a primary flight feather
Flight Feathers: the large wing and tail feathers that provide lift and maneuverability in flight (see "Remiges" and "Rectrices")
Immature: a young bird in its first year, before it has acquired adult plumage.
Notch: a distinct narrowing in the posterior
vane of a primary flight feather.
Pennaceous Barbs: barbs with interlocking
barbules that form a coherent vane
Plumulaceous Barbs: barbs without interlocking
barbules, forming a loose fluffy layer at the base of a contour
feather; or making up the entirety of a down feather.
Primary: one of the wing's outer flight
feathers, which are attached to the fused bones of the bird's
"hand." Most bird species have 9-10 primaries.
Rachis: the upper portion of the feather
shaft, to which the barbs are attached.
Remiges: the flight feathers of the wing,
including the primaries, secondaries, and tertials.
Rectrices: the flight feathers of the tail.
Most bird species have 10-12 rectrices.
Secondary: one of the wing's inner flight
feathers, which are attached to the ulna bone in the bird's
"forearm." The number of secondaries varies from
9-25 depending on the species.
Subadult: a bird that is not fully adult, in species that require more than one year to achieve adult plumage (e.g. eagles). In such species, age is often estimated by plumage stage (e.g., Subadult I, II, and III for Bald Eagles).
Tertial: the innermost flight flight feathers
of the wing, attached to the humerus bone in the bird's upper
arm. There are usually 3-4 tertials.
Vane: the smooth feather surface formed
by the interlocked pennaceous barbs. On remiges, the anterior
vane is on the forward side of the rachis (the leading edge).
The posterior vane is the trailing edge of the feather.
Ventral: the under surface of the body, or of any body part oriented in a normal horizontal postion. The Feather Atlas illustrates feathers in ventral view only when the under surface is very different from the upper surface (e.g., in Black and Turkey Vultures).
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