Gape
Encyclopedia
In bird anatomy
, the gape is the interior of the open mouth of a bird and the gape flange is the region where the two mandible
s join together, at the base of the beak
. The width of the gape can be factor in the choice of food.
Gapes of juvenile altricial
birds are often brightly colored, sometimes with contrasting spots or other patterns, and these are believed to be an indication of their health, fitness and competitive ability. Based on this, the parents decide how to distribute food among the chicks in the nest. Some species especially in the families Viduidae and Estrildidae have bright spots on the gape known as gape tubercles or gape papillae. These nodular spots are conspicuous even in low light. A study examining the nestling gapes of eight passerine
species found that the gapes were conspicuous in the ultraviolet
spectrum (visible to birds but not to humans). Parents may however not rely solely on the gape coloration, and other factors influencing their decision remain unknown.
Red gape color has been shown in several experiments to induce feeding. An experiment in manipulating brood size and immune system with Barn Swallow
nestlings showed the vividness of the gape was positively correlated
with T-cell–mediated immunocompetence
, and that larger brood size and injection with an antigen
led to a less vivid gape. Conversely, the red gape of the Common Cuckoo
(Cuculus canorus) did not induce extra feeding in host parents. Some brood parasite
s such as the Hodgson's Hawk-cuckoo
(C. fugax) have colored patches on the wing that mimic the gape color of the parasitized species.
When born, the chick's gape flanges are fleshy. As it grows into a fledgling
, the gape flanges remain somewhat swollen and can thus be used to recognize that a particular bird is young. By the time it reaches adulthood, the gape flanges will no longer be visible.
Bird anatomy
Bird anatomy, or the physiological structure of birds' bodies, shows many unique adaptations, mostly aiding flight. Birds have a light skeletal system and light but powerful musculature which, along with circulatory and respiratory systems capable of very high metabolic rates and oxygen supply,...
, the gape is the interior of the open mouth of a bird and the gape flange is the region where the two mandible
Mandible
The mandible pronunciation or inferior maxillary bone forms the lower jaw and holds the lower teeth in place...
s join together, at the base of the beak
Beak
The beak, bill or rostrum is an external anatomical structure of birds which is used for eating and for grooming, manipulating objects, killing prey, fighting, probing for food, courtship and feeding young...
. The width of the gape can be factor in the choice of food.
Altricial
Altricial, meaning "requiring nourishment", refers to a pattern of growth and development in organisms which are incapable of moving around on their own soon after hatching or being born...
birds are often brightly colored, sometimes with contrasting spots or other patterns, and these are believed to be an indication of their health, fitness and competitive ability. Based on this, the parents decide how to distribute food among the chicks in the nest. Some species especially in the families Viduidae and Estrildidae have bright spots on the gape known as gape tubercles or gape papillae. These nodular spots are conspicuous even in low light. A study examining the nestling gapes of eight passerine
Passerine
A passerine is a bird of the order Passeriformes, which includes more than half of all bird species. Sometimes known as perching birds or, less accurately, as songbirds, the passerines form one of the most diverse terrestrial vertebrate orders: with over 5,000 identified species, it has roughly...
species found that the gapes were conspicuous in the ultraviolet
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
spectrum (visible to birds but not to humans). Parents may however not rely solely on the gape coloration, and other factors influencing their decision remain unknown.
Red gape color has been shown in several experiments to induce feeding. An experiment in manipulating brood size and immune system with Barn Swallow
Barn Swallow
The Barn Swallow is the most widespread species of swallow in the world. It is a distinctive passerine bird with blue upperparts, a long, deeply forked tail and curved, pointed wings. It is found in Europe, Asia, Africa and the Americas...
nestlings showed the vividness of the gape was positively correlated
Correlation
In statistics, dependence refers to any statistical relationship between two random variables or two sets of data. Correlation refers to any of a broad class of statistical relationships involving dependence....
with T-cell–mediated immunocompetence
Immunocompetence
Immunocompetence is the ability of the body to produce a normal immune response following exposure to an antigen. Immunocompetence is the opposite of immunodeficiency or immuno-incompetent or immuno-compromised...
, and that larger brood size and injection with an antigen
Antigen
An antigen is a foreign molecule that, when introduced into the body, triggers the production of an antibody by the immune system. The immune system will then kill or neutralize the antigen that is recognized as a foreign and potentially harmful invader. These invaders can be molecules such as...
led to a less vivid gape. Conversely, the red gape of the Common Cuckoo
Common Cuckoo
The Common Cuckoo is a member of the cuckoo order of birds, Cuculiformes, which includes the roadrunners, the anis and the coucals....
(Cuculus canorus) did not induce extra feeding in host parents. Some brood parasite
Brood parasite
Brood parasites are organisms that use the strategy of brood parasitism, a kind of kleptoparasitism found among birds, fish or insects, involving the manipulation and use of host individuals either of the same or different species to raise the young of the brood-parasite...
s such as the Hodgson's Hawk-cuckoo
Hodgson's Hawk-cuckoo
The Hodgson's Hawk-Cuckoo, Cuculus fugax is a species of cuckoo found in south, east and southeast Asia.Hodgson's Hawk-Cuckoo is a brood parasite. The chick evicts bona fide residents of the parasitized nest, thus becoming the sole occupant. Under normal circumstances, this would reduce the...
(C. fugax) have colored patches on the wing that mimic the gape color of the parasitized species.
When born, the chick's gape flanges are fleshy. As it grows into a fledgling
Fledge
Fledge is the stage in a young bird's life when the feathers and wing muscles are sufficiently developed for flight. It also describes the act of a chick's parents raising it to a fully grown state...
, the gape flanges remain somewhat swollen and can thus be used to recognize that a particular bird is young. By the time it reaches adulthood, the gape flanges will no longer be visible.