A frontal shield, also known as a facial shield or frontal plate, is a feature of the anatomy of several bird species. Located just above the upper mandible, and protruding along the forehead, it is composed of two main parts: a hard, proteinaceous callus and a soft, fleshy corium. It is thought to play roles in protection, mate identification, sexual selection, and territorial defense.
The callus is a hard, keratinous section of the frontal plate located highest on the forehead. It is generally more pigmented than the surrounding corium. Underneath the callus is a Malpighian layer of tissue that connects the structure to the maxilla. This layer is supplied with blood via vessel-containing dermal papillae. It has been observed to resemble the texture of calloused human skin. The corium is a thick, dense mass of connective tissue fibers that makes up the largest portion of the frontal plate. It contains layers of cells that aide in enlarging or flattening the structure. The corium may also be pigmented, but is clearly delineated from the callus by size and texture. A posterior muscle attachment and cell layers within the corium allow it to change shape between enlarged, semi-enlarged, and flattened. The cell layers become vacuolated to cause enlargement, and may return to normal to cause flattening.
A strong correlation between frontal plate state and season has been observed. During winter months, the frontal plate remains flattened and small. This may help to protect the tissue from cold conditions. During the breeding season in the warmer months, the frontal plate becomes enlarged as a method to attract mates, and scare away other individuals competing for a mate. The fully enlarged form of the frontal plate can be double the size when flattened. Territorial males will enlarge their corium and raise the feathers on the back of their neck to appear larger and more threatening to competing males. Research has also suggested that the shape of the callus serves as an identifying feature for mating pairs. Birds have been observed to show aggression towards another individual in their territory until that individual's frontal plate is fully visible. After recognition, normal pair behavior commences. It consists of a hard or fleshy plate of specialised skin extending from the base of the upper bill over the forehead. The size, shape and colour may exhibit testosterone-dependent variation in either sex during the year. [1] Functionality appears to relate to protection of the face while feeding in, or moving through, dense vegetation, as well as to courtship display and territorial defence. [2] It is a characteristic of some water birds in the rail family, especially the gallinules and moorhens, swamphens and coots, as well as in the Jacana family. [3] [4] The watercock's frontal shield is extended above the head into a horn-like protuberance. A bird from a different order, the extinct Choiseul pigeon, had a blue frontal shield.
The rails, or Rallidae, are a large cosmopolitan family of small- to medium-sized, ground-living birds. The family exhibits considerable diversity and includes the crakes, coots, and gallinules. Many species are associated with wetlands, although the family is found in every terrestrial habitat except dry deserts, polar regions, and alpine areas above the snow line. Members of the Rallidae occur on every continent except Antarctica. Numerous island species are known. The most common rail habitats are marshland and dense forest. They are especially fond of dense vegetation.
The common moorhen, also known as the waterhen or swamp chicken, is a bird species in the rail family (Rallidae). It is distributed across many parts of the Old World.
Coots are medium-sized water birds that are members of the rail family, Rallidae. They constitute the genus Fulica, the name being the Latin term for "coot". Coots have predominantly black plumage, and—unlike many rails—they are usually easy to see, often swimming in open water. They are close relatives of the moorhen. However, the Coot typically appears 'dumpier' and lacks the distinctive red frontal face of the moorhen.
In anatomy, the meninges are the three membranes that envelop the brain and spinal cord. In mammals, the meninges are the dura mater, the arachnoid mater, and the pia mater. Cerebrospinal fluid is located in the subarachnoid space between the arachnoid mater and the pia mater. The primary function of the meninges is to protect the central nervous system.
The bronze-winged jacana is a wader in the family Jacanidae. It is found across South and Southeast Asia and is the sole species in the genus Metopidius. Like other jacanas it forages on lilies and other floating aquatic vegetation, the long feet spreading out its weight and preventing sinking. The sexes are alike but females are slightly larger and are polyandrous, maintaining a harem of males during the breeding season in the monsoon rains. Males maintain territories, with one male in the harem chosen to incubate the eggs and take care of the young. When threatened, young chicks may be carried to safety by the male under his wings.
The white swamphen, also known as the Lord Howe swamphen, Lord Howe gallinule or white gallinule, is an extinct species of rail which lived on Lord Howe Island, east of Australia. It was first encountered when the crews of British ships visited the island between 1788 and 1790, and all contemporary accounts and illustrations were produced during this time. Today, two skins exist: the holotype in the Natural History Museum of Vienna, and another in Liverpool's World Museum. Although historical confusion has existed about the provenance of the specimens and the classification and anatomy of the bird, it is now thought to have been a distinct species endemic to Lord Howe Island and most similar to the Australasian swamphen. Subfossil bones have also been discovered since.
The watercock is a waterbird in the rail and crake family, Rallidae that is widely distributed across Southeast Asia. It is the only member of the genus Gallicrex.
The dusky moorhen is a bird species in the rail family and is one of the eight extant species in the moorhen genus. It occurs in India, Australia, New Guinea, Borneo and Indonesia. It is often confused with the purple swamphen and the Eurasian coot due to similar appearance and overlapping distributions. They often live alongside birds in the same genus, such as the Tasmanian nativehen and the common moorhen.
The northern jacana or northern jaçana is a wader which is known as a resident breeder from coastal Mexico to western Panama, and on Cuba, Jamaica and Hispaniola in the Caribbean. It sometimes known to breed in Texas, United States, and has also been recorded on several occasions as a vagrant in Arizona. The jacanas are a group of wetland birds, which are identifiable by their huge feet and claws, which enable them to walk on floating vegetation in the shallow lakes that are their preferred habitat. In Jamaica, this bird is also known as the 'Jesus bird', as it appears to walk on water. Jacana is Linnæus' scientific Latin spelling of the Brazilian Portuguese jaçanã, pronounced [ʒasaˈnɐ̃], from the Tupi name of the bird. See jacana for pronunciations.
A dewlap is a longitudinal flap of skin or similar flesh that hangs beneath the lower jaw or neck of many vertebrates. More loosely, it can be various similar structures in the neck area, such as those caused by a double chin or the submandibular vocal sac of a frog. More generally, it can be any hanging mass of skin, such as a fold of loose skin on an elderly person's neck, or the wattle of a bird. Dewlaps can be considered as a caruncle, defined as "a small, fleshy excrescence that is a normal part of an animal's anatomy".
The crown is the top portion of the head behind the vertex. The anatomy of the crown varies between different organisms. The human crown is made of three layers of the scalp above the skull. The crown also covers a range of bone sutures, and contains blood vessels and branches of the trigeminal nerve.
The frontal sinuses are one of the four pairs of paranasal sinuses that are situated behind the brow ridges. Sinuses are mucosa-lined airspaces within the bones of the face and skull. Each opens into the anterior part of the corresponding middle nasal meatus of the nose through the frontonasal duct which traverses the anterior part of the labyrinth of the ethmoid. These structures then open into the semilunar hiatus in the middle meatus.
A horse hoof is the lower extremity of each leg of a horse, the part that makes contact with the ground and carries the weight of the animal. It is both hard and flexible. It is a complex structure surrounding the distal phalanx of the 3rd digit of each of the four limbs, which is covered by soft tissue and keratinised (cornified) matter.
A wattle is a fleshy caruncle hanging from various parts of the head or neck in several groups of birds and mammals. Caruncles in birds include those found on the face, wattles, dewlaps, snoods, and earlobes. Wattles are generally paired structures, but may occur as a single structure when it is sometimes known as a dewlap. Wattles are frequently organs of sexual dimorphism. In some birds, caruncles are erectile tissue and may or may not have a feather covering.
Jacana is the genus comprising the two jacanas of the Americas: the northern jacana, Jacana spinosa, and the wattled jacana, Jacana jacana.
A caruncle is defined as 'a small, fleshy excrescence that is a normal part of an animal's anatomy'. Within this definition, caruncles in birds include wattles, combs, snoods, and earlobes. The term caruncle is derived from Latin caruncula, the diminutive of carō, "flesh".
The Hawaiian gallinule is an endangered chicken-sized water bird in the rail family. It is also variously known as the Hawaiian common gallinule, Hawaiian moorhen, Hawaiian common moorhen, mudhen, or `alae `ula in Hawaiian, and sometimes misleadingly as the Hawaiian red coot. It is a subspecies of the common gallinule that is endemic to the tropical Hawaiian Islands of the north-central Pacific Ocean.
Gullion, Gordon W. The Wilson Bulletin Vol. 63, No. 3 (Sep., 1951), pp. 157–166