Flamingo

Flamingos Temporal range: Oligocene-Holocene, 25–0Ma PreЄ Є O S D C P T J K Pg N
James's Flamingos (P. jamesi) at Laguna Colorada
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Order:	Phoenicopteriformes
Family:	Phoenicopteridae
Genus:	Phoenicopterus Linnaeus, 1758
Species
See text
Global distribution of the flamingos

Flamingos or Flamingoes^[1] ( Brazilian pronunciation (help·info)) are a type of wading bird in the genus Phoenicopterus (from Greek: φοινικόπτερος, meaning "purple wing"), the only genus in the family Phoenicopteridae. There are four flamingo species in the Americas and two species in the Old World.

Taxonomy and systematics

A wide variety of birds have been proposed as their closest relatives, on a wide variety of evidence. As a result, flamingos are generally placed in their own order.^{[citation needed]}

Traditionally, the long-legged Ciconiiformes, probably a paraphyletic assemblage, have been considered the flamingos' closest relatives and the family was included in the order. Usually the ibises and spoonbills of the Threskiornithidae were considered their closest relatives within this order. Earlier genetic studies, such as those of Charles Sibley and colleagues, also supported this relationship.^[2] Relationships to the waterfowl were considered as well,^[3] especially as flamingos are parasitized by feather lice of the genus Anaticola, which are otherwise exclusively found on ducks and geese.^[4] The peculiar presbyornithids were used to argue for a close relationship between flamingos, waterfowl, and waders,^[5] but they are now known to be unequivocal waterfowl.^[6]

Relationship with grebes

Many molecular and morphological studies support a relationship between grebes and flamingos

Recent molecular studies have suggested a relation with grebes,^[7][8][9] while morphological evidence also strongly supports a relationship between flamingos and grebes. They hold at least eleven morphological traits in common, which are not found on other birds. Many of these characteristics have been previously identified on flamingos, but not on grebes.^[10] The fossil Palaelodids can be considered evolutionarily, and ecologically, intermediate between flamingos and grebes.^[11]

For the grebe-flamingo clade, the taxon Mirandornithes ("miraculous birds" due to their extreme divergence and apomorphies) has been proposed. Alternatively, they could be placed in one order, with Phoenocopteriformes taking priority.^[11]

Species

Six flamingo species are recognized by most sources, and these are generally placed in one genus. Two species, the Andean and the James's Flamingo, are often placed in the genus Phoenicoparrus instead of Phoenicopterus.^{[citation needed]}

• Prehistoric species of flamingo:^{[citation needed]}
  • Phoenicopterus croizeti (Middle Oligocene – Middle Miocene of C Europe)
  • Phoenicopterus floridanus (Early Pliocene of Florida)
  • Phoenicopterus stocki (Middle Pliocene of Rincón, Mexico)
  • Phoenicopterus copei (Late Pleistocene of W North America and C Mexico)
  • Phoenicopterus minutus (Late Pleistocene of California, USA)
  • Phoenicopterus aethiopicus
  • Phoenicopterus eyrensis (Late Oligocene of South Australia)

Description

The arcuate bill of this American Flamingo is well adapted to bottom scooping

Flying flamingos over Namibia

Flamingos often stand on one leg, the other leg tucked beneath the body. The reason for this behavior is not fully understood. Recent research indicates that standing on one leg may allow the birds to conserve more body heat, given that they spend a significant amount of time wading in cold water.^[12] However, the behaviour also takes place in warm water. As well as standing in the water, flamingos may stamp their webbed feet in the mud to stir up food from the bottom.^{[citation needed]}

Young flamingos hatch with greyish reddish plumage, but adults range from light pink to bright red due to aqueous bacteria and beta-Carotene obtained from their food supply. A well-fed, healthy flamingo is more vibrantly coloured and thus a more desirable mate; a white or pale flamingo, however, is usually unhealthy or malnourished. Captive flamingos are a notable exception; many turn a pale pink as they are not fed carotene at levels comparable to the wild.^{[citation needed]}

Circulatory System

Although there has been little investigation on the specific circulatory and cardiovascular system of flamingos, they possess the typical features of an avian circulatory system. As is seen in other aves, the flamingo’s circulatory system is closed maintaining a separation of oxygenated and deoxygenated blood. This maximizes their efficiency to meet their high metabolic needs during flight. Due to this need for increased cardiac output, the avian heart tends to be larger in relation to body mass than what is seen in most mammals.

Heart type and features

The avian circulatory system is driven by a four-chambered, myogenic heart contained in a fibrous pericardial sac. This pericardial sac is filled with a serous fluid for lubrication.^[13] The heart itself is divided into a right and left half, each with an atrium and ventricle. The atrium and ventricles of each side are separated by atrioventricular valves which prevent back flow from one chamber to the next during contraction. Being myogenic, the hearts pace is maintained by pacemaker cells found in the sinoatrial node, located on the right atrium. The sinoatrial node uses calcium to cause a depolarizing signal transduction pathway from the atrium through right and left atrioventricular bundle which communicates contraction to the ventricles. The avian heart also consists of muscular arches that are made up of thick bundles of muscular layers. Much like a mammalian heart, the avian heart is composed of endocardial, myocardial and epicardial layers.^[13] The atrium walls tend to be thinner than the ventricle walls, due to the intense ventricular contraction used to pump oxygenated blood throughout the body.

Organization of Circulatory System

Similar to the atrium, the arteries are composed of thick elastic muscles to withstand the pressure of the ventricular constriction, and become more rigid as they move away from the heart. Blood moves through the arteries, which undergo vasoconstriction, and into arterioles which act as a transportation system to distribute primarily oxygen as well as nutrients to all tissues of the body.^[14] As the arterioles move away from the heart and into individual organs and tissues they are further divided to increase surface area and slow blood flow. Travelling through the arterioles blood moves into the capillaries where gas exchange can occur. Capillaries are organized into capillary beds in tissues, it is here that blood exchanges oxygen for carbon dioxide waste. In the capillary beds blood flow is slowed to allow maximum diffusion of oxygen into the tissues. Once the blood has become deoxygenated it travels through venules then veins and back to the heart. Veins, unlike arteries, are thin and rigid as they do not need to withstand extreme pressure. As blood travels through the venules to the veins a funneling occurs called vasodilation bringing blood back to the heart.^[14] Once the blood reaches the heart it moves first into the right atrium, then the left ventricle to be pumped through the lungs for further gas exchange of carbon dioxide waste for oxygen. Oxygenated blood then flows from the lungs through the left atrium to the left ventricle where it is pumped out to the body.

Flamingo blood composition

It was widely thought that avian blood had special properties which attributed to a very efficient extraction and transportation of oxygen in comparison to mammalian blood. This of course is not true; there is no real difference in the efficiency of the blood, and both mammals and birds use a hemoglobin molecule as the primary oxygen carrier with little to no difference in oxygen carrying capacity.^[15] Captivity and age have been seen to have an effect on the blood composition of the American Flamingo (Phoenicopterus ruber). A decrease in white blood cell numbers was predominate with age in both captive and free living flamingos, but captive flamingos showed a higher white blood cell count than free living flamingos.^[16] One exception occurs in free living flamingos with regards to white blood cell count. The number of eosinophils in free living birds are higher because these cells are the ones that fight off parasites which a free living bird may have more contact with than a captive one. Captive birds showed higher hematocrit and red blood cell numbers than the free living flamingos, and a blood hemoglobin increase was seen with age.^[16] An increase in hemoglobin would correspond with an adults increase in metabolic needs. A smaller mean cellular volume recorded in free living flamingos coupled with similar mean hemoglobin content between captive and free living flamingos could show different oxygen diffusion characteristics between these two groups.^[16] Plasma chemistry remains relatively stable with age but lower values of protein content, uric acid, cholesterol, triglycerides, and phospholipids were seen in free living flamingos. This trend can be attributed to shortages and variances in food intake in free living flamingos.^[16]

Physical and chemical properties of pumping blood

Avian hearts are generally larger than mammalian hearts when compared to body mass. This adaptation allows more blood to be pumped to meet the high metabolic need associated with flight. Birds, like the flamingo, have a very efficient system for diffusing oxygen into the blood; birds have a ten times greater surface area to gas exchange volume than mammals. As a result, birds have more blood in their capillaries per unit of volume of lung than a mammal.^[15] The Flamingo’s (Phoenicopterus ruber) four chambered heart is myogenic meaning that all the muscle cells and fibers have the ability to contract rhythmically.^[17] The rhythm of contraction is controlled by the pace maker cells which have a lower threshold for depolarization. The wave of electrical depolarization initiated here is what physically starts the heart’s contractions and begins pumping blood. Pumping blood creates variations in blood pressure and as a result, creates different thicknesses of blood vessels. The Law of LaPlace can be used to explain why arteries are relatively thick and veins are thin.

Behaviour and ecology

Feeding

Flamingos filter-feed on brine shrimp and blue-green algae. Their beaks are specially adapted to separate mud and silt from the food they eat, and are uniquely used upside-down. The filtering of food items is assisted by hairy structures called lamellae which line the mandibles, and the large rough-surfaced tongue. The pink or reddish color of flamingos comes from carotenoids in their diet of animal and plant plankton. These carotenoids are broken down into pigments by liver enzymes.^[18] The source of this varies by species, and affects the saturation of color. Flamingos whose sole diet is blue-green algae are darker in color compared to those who get it second hand (e.g. from animals that have digested blue-green algae).^[19]

Lifecycle

American Flamingo and offspring

Colony of flamingos at Lake Nakuru

Flamingos are very social birds; they live in colonies whose population can number in the thousands. These large colonies are believed to serve three purposes for the flamingos: avoiding predators, maximizing food intake, and using scarce suitable nesting sites more efficiently.^[20] Before breeding, flamingo colonies split into breeding groups of between about 15 and 50 birds. Both males and females in these groups perform synchronized ritual displays.^[21] The members of a group stand together and display to each other by stretching their necks upwards, then uttering calls while head-flagging, and then flapping their wings.^[22] The displays do not seem to be directed towards an individual but instead occur randomly.^[22] These displays stimulate "synchronous nesting" (see below) and help pair up those birds who do not already have mates.^[21]

Flamingoes form strong pair bonds of one male and one female, although in larger colonies flamingos sometimes change mates, presumably because there are more mates to choose from).^[23] Flamingo pairs establish and defend nesting territories. They locate a suitable spot on the mudflat to build a nest (the spot is usually chosen by the female).^[22] It is during nest building that copulation usually occurs. Nest building is sometimes interrupted by another flamingo pair trying to commandeer the nesting site for their own use. Flamingos aggressively defend their nesting sites. Both the male and the female contribute to building the nest, and to defending the nest and egg.^{[citation needed]}

After the chicks hatch, the only parental expense is feeding.^[24] Both the male and the female feed their chicks with a kind of crop milk, produced in glands lining the whole of the upper digestive tract (not just the crop). Production is stimulated by a hormone called prolactin. The milk contains fat, protein, and red and white blood cells. (Pigeons and doves—Columbidae—also produce a crop milk (just in the glands lining the crop), which contains less fat and more protein than flamingo crop milk.)^{[citation needed]}

For the first six days after the chicks hatch, the adults and chicks stay in the nesting sites. At around seven to twelve days old, the chicks begin to move out of their nests and explore their surroundings. When they are two weeks old, the chicks congregate in groups, called "microcrèches", and their parents leave them alone. After a while, the microcrèches merge into "crèches" containing thousands of chicks. Chicks that do not stay in their crèches are vulnerable to predators.^[25]

Status and conservation

In captivity

The first flamingo hatched in a European zoo was a Chilean Flamingo at Zoo Basel in Switzerland in 1958. Since then, over 389 flamingos have grown up in Basel and been distributed to other zoos around the globe.^[26]

An 83-year-old Greater Flamingo, believed to be the oldest in the world, died at the Adelaide Zoo in Australia in January, 2014.^[27]

Relationship with humans

Moche Ceramic Depicting Flamingo (200 AD) Larco Museum Collection Lima, Peru

The Old World flamingos were considered by the Ancient Egyptians to be the living representation of the god Ra,^[28] while in Ancient Rome, their tongues were considered a delicacy.^[29]

In the Americas, the Moche people of ancient Peru worshipped nature.^[30] They placed emphasis on animals and often depicted flamingos in their art,^[31] while in The Bahamas they are the national bird. Also, Andean miners have killed flamingos for their fat, believed to be a cure for tuberculosis.^[32] In the United States, pink plastic flamingo statues are popular lawn ornaments.^[33]

Brooklyn Museum - American Flamingo - John J. Audubon

References

External links

Wikispecies has information related to: Phoenicopteridae

Wikimedia Commons has media related to Phoenicopterus.

• IUCN/Wetlands International Flamingo Specialist Group
• Flamingo Resource Centre
• Flamingo videos and photos on the Internet Bird Collection