Altricial – describes birds that hatch with little to no downy feathers and are relatively immobile, such young must be fed by adults and need time to develop before leaving the nest. Most passerines are altricial. Altricial is the opposite of precocial. Eagles are considered semi-altricial.
Alula – Also called bastard wing, this projection on the front edge of the wing typically has three to five feathers which can be spread when flying slowly to keep the bird from stalling. The alula is the first digit, anatomically analogous to the thumb.
Anklet – Part of the equipment worn by captive birds of prey, the anklet is a leather band that fastens around the leg. Also referred to as bracelet. Jesses attach to the anklet.
Asynchronous – Describes hatching in a clutch of eggs that occurs over a period of several days rather than all the eggs hatching together
Bi-colored beak – describes a beak of two colors; Immature bald eagles have a bi-colored beak which is dark, blue-black and lighter toward the base. As juvenile bald eagles mature the beak color gets lighter from the base outward, gradually becoming the light yellow of the adult bald eagle.
Booted eagles – one of the four major groups of eagles; Booted eagles have feathers on their entire leg, including on their tarsometatarsi, up to their toes. Golden eagles are part of the booted eagle family. Also called True eagles.
Branching – a behavior common in eaglets just before fledging. In branching, eaglets move from the nest to a branch and flap their wings and jump off the branch. This behavior serves to strengthen flight muscles and acclimate the eaglet to life outside the nest.
Bumblefoot – a condition typified by sores on the bottom of a bird’s foot caused by infection and inflammatory reaction; It is somewhat analogous to bedsores in humans and can be caused by inappropriate or insufficient variety of perches, poor nutrition, obesity and/or inactivity or a compromised immune system. Captive birds are more susceptible to bumblefoot than non-captive birds.
Buteo – genus of hawks typified by long, broad, rounded wings and shorter, rounded tails; includes red-tailed, rough-legged, broad-winged and red-shouldered hawks that are often seen soaring with wings and tails spread
Cere – fleshy region at the base of the beak that surrounds the nostrils. See Photo
Cervical vertebrae – vertebrae (bones) in the neck region. Raptors have 14 cervical vertebrae that allow them to turn their necks 180 degrees or more. In contrast, humans have only 7 cervical vertebrae and can rotate their heads just 70-90 degrees in either direction.
Cloaca – Posterior opening common to the intestinal, urinary and generative systems. In birds, also called the vent.
Cloacal kiss – in copulation, when male and female cloacas touch and sperm is transferred from male to female
Complete migration – all individuals of a species leave the breeding range during nonbreeding season
Copulation – mating, act that accomplishes the transfer of sperm from male to female; see cloacal kiss
Coverts – contour feathers found on body, usually named for their location on the bird, e.g. primary coverts
Egg tooth – Hatchling eaglets have a special notch on their beak to facilitate pipping. This pip tooth or egg tooth falls off several days after hatching.
Endangered species – a species that has been identified as under threat of extinction or extirpation; In the United States, the US Fish and Wildlife Service maintains an official list of species that are considered endangered and threatened or of special concern. Internationally, the International Union for the Conservation of Nature (IUCN) maintains listings of more than 49,000 species, subspecies and varieties of flora and fauna and places each in a category based on the level of threats that species is facing in the wild.
Extirpation – the loss of a species from a particular part of its natural range; e.g The bald eagle was nearly extirpated from the continental US. Populations in Alaska and Canada remained healthy even while bald eagles were rare in the lower 48 states.
Falcon – a member of the family Falconidae and the genus Falco, characterized by long pointed wings, dark eyes and medium to long tails along with the other raptor characteristics of hooked beaks, sharp talons, and keen eyesight. Falcon species include Peregrine Falcons, Kestrels, Merlins and Prairie Falcons and many others.
Gizzard – part of the stomach in many birds that contains small stones or gravel which is used to break down food mechanically. Raptors do not use the gizzard to digest their food. Instead, raptors digest food with powerful stomach acids.
Glide – coasting downward in flight without flapping. It is the opposite of Soar.
Harpy eagles – refers to a particular species of eagle, Harpia harpyja, found in Central America; Also refers to one of the four major groups of eagles around the world. The harpy eagle group also includes the Papuan Eagle, Harpyopsis novaeguineae, of New Guinea.
Hopscotch – describes a particular migration pattern in which the northern most birds migrate farther south than some year round residents of the same species. As an example, red-tailed hawks in Minnesota may stay year round, while some of the birds from Canada migrate to an area south of Minnesota.
Hovering – flap flying in place; hoveringis very energy intensive and most commonly seen in kestrels and rough-legged hawks. (contrast with Kiting)
Imping – the process of repairing a flight feather by joining the broken feather to an intact feather (which may be a previously molted feather) by joining the two feather shafts
Imprinting – describes a psychological process where a young bird or animal identifies with a figure present early in life; birds raised by humans form inappropriate bonds with humans and may later be unable to form pair bonds with their own species; imprinted birds are typically unable to be released to the wild
Jess – strap (traditionally leather) that attaches to the anklet of a captive bird of prey. See Photo
Kite or Kiting – flying in one place without flapping (contrast with Hovering)
Lore(s) – the region between the eyes and nostrils of a bird, reptile or amphibian. See Photo
Lure – a falconry tool that is used to train a bird of prey; Food is attached to the lure which is then swung around on a long rope and thrown for the raptor to seize. Lures are typically made of leather cut in the shape of a bird.
Molt – the natural process of replacing feathers; Raptors molt once a year, usually in spring and summer. They tend to molt symmetrically meaning if they lose the third primary on the right, they also lose the third primary on the left. Raptors do not lose all their flight feathers at one time and are never rendered flightless by a molt. It can take up to four years for an eagle to complete a molt.
Mutes – bodily waste of a raptor that includes urine and feces; There are three parts to a mute: fecal – the semi-solid mass, frequently this is dark in color. Urate – white, chalky material – the crystalline uric acid that is the result of protein metabolism. Urine – clear water that flushes the waste from the system.
Nictitating membrane – also known as “the third eyelid”; closes from the interior edge out to the side; The membrane cleans and protects the eye. See Photo where membrane is partially covering the eyeball and appears as a cloudy film over the eye.
Opportunistic predator – describes predation pattern of animals that hunt when necessary and scavenge when carrion is available
Osprey – Padion haliaetus; a raptor that feeds almost exclusively on fish, sometimes called a fish hawk; Osprey are able to catch fish in deeper water than bald eagles because they can dive below the surface of the water. An osprey’s toe is reversible, allowing them to grasp their prey with two toes in front and two behind or three toes in front and one behind (as an eagle would grasp).
Partial Migration – some members of a population leave the breeding range during nonbreeding season while others remain in the breeding range year round
Passerine – bird of the order Passeriformes, which includes more than half of all bird species. Sometimes known as perching birds or, less accurately, as songbirds.
Patagium – the leading edge of the wing between the shoulder and the wrist
In Red-tailed Hawks the dark patagial line is one of the best field marks.
Pellet – indigestible food regurgitated by a bird; In the case of eagles, a pellet consists only of fur or feathers. Other raptors, such as owls, also regurgitate bones in their pellet along with the fur of animals they consume. See Photo of an eagle pellet – note no bones in the pellet.
Photo period – the period of daylight in every 24 hours; varies seasonally except at the equator. In the northern hemisphere, the photo period is longest on June 21st and shortest on December 21st. For many birds, the timing of biologic processes such as molting and breeding can be triggered by changes in the photo period.
Precocial – young that are born or hatched with some downy feathers and are mobile and able to flee or defend themselves from predators; opposite of altricial, describing young that need time to mature before leaving the nest.
Prey – an organism that is hunted by predator, food source for predators
Race – subspecies; Although races are distinct within species, they can interbreed. It was previously thought that there were two distinct races of bald eagles, a northern and a southern race, due to the significant size differences between the northern and southern populations. Few sources refer to different races of the bald eagle today. e.g. There are three distinct races of Peregrine Falcon in the US.
Rouse – when the bird raises all her feathers and shakes, a sign of contentment
Sea eagles – see Fish eagles
Semi-altricial – an animal or bird that is born or hatched not yet ready to survive independently, but has some fur or downy feathers; eagles are semi-altricial
Siblicide – the killing of a sibling; eaglets and other young raptors sometimes engage in silicide, particularly when food is scarce
Snake eagles – one of the four major groups of eagles around the world; feed primarily on snakes; Group includes Short-toed Snake Eagle (Circaetus gallicus), Black-chested Snake Eagle (Circaetus pectoralis) and Brown Snake Eagle (Circaetus cinereus)
Soar – upward flight without flapping; often done making use of a thermal, a column of rising warm air; Once at the top of a thermal the raptor will often glide to another thermal. Wings are usually fully extended in a soar.
Species – A grouping of birds or animals that can interbreed. A species name is typically denoted with a two word Latin name that identifies both the genus and the species. Bald eagles are Haliaeetus leucocephalus. Golden eagles are Aquila chrysaetos.
Stoop – fast dive by a bird of prey with the wings tucked close to the body, usually in pursuit of prey
Supraorbital ridge – the boney protuberance above the eye socket; this ridge helps shade and protect the eye and gives raptors their fierce look
Tarsometatarsus (pl. Tarsometatarsi) – a bone that is only found in the lower leg of birds and certain dinosaurs; the tarsometatarsus is formed from the fusion of several bones found in other types of animals and homologous to the mammalian tarsal (ankle) and metatarsal (foot) bones. The tarsometatarsus of birds is often referred to as just the tarsus or metatarsus.
Territory – area around the nest defended by the eagles; also breeding territory
Tri-colored beak – golden eagles have a distinctly colored beak that is dark at the tip, bluish gray in the middle and light at the base. The tri-color does not include the yellow cere at the base of the beak. The cere is not part of the beak. See Photo
True eagles – one of the four major groups of eagles; True or booted eagles have feathers on their entire leg, including on their tarsometatarsi, up to their toes. Golden eagles are part of the true or booted eagle family.
Ulna – bone in the wing extending from the wrist to the elbow; the secondary flight feathers attach to the ulna