The darters, anhingas, or snakebirds are mainly tropical waterbirds in the family Anhingidae, which contains a single genus, Anhinga. There are four living species, three of which are very common and widespread while the fourth is rarer and classified as near-threatened by the IUCN. The term snakebird is usually used without any additions to signify whichever of the completely allopatric species occurs in any one region. It refers to their long thin neck, which has a snake-like appearance when they swim with their bodies submerged, or when mated pairs twist it during their bonding displays. "Darter" is used with a term when referring to particular species. It alludes to their manner of procuring food, as they impale with their thin, pointed beak. The American darter ( A. anhinga) is more commonly known as the anhinga. It is sometimes called "water turkey" in the southern United States; though the anhinga is quite unrelated to the wild turkey, they are both large, blackish birds with long tails that are sometimes hunted for food.[Answers.com 2009, BLI (2009), Myers et al. 2009]
Description
Anhingidae are large birds with sexually dimorphic
plumage. They measure about in length, with a wingspan around , and weigh some . The males have black and dark-brown plumage, a short erectile crest on the nape and a larger bill than the female. The females have much paler plumage, especially on the neck and underparts, and are a bit larger overall. Both have grey stippling on long
and upper
. The sharply pointed
beak has serrated edges, a
palate and no external
. The darters have completely
webbed feet, and their legs are short and set far back on the body.
[Brodkorb & Mourer-Chauviré (1982), Myers et al. 2009]
There is no eclipse plumage, but the bare parts vary in color around the year. During breeding, however, their small gular sac changes from pink or yellow to black, and the bare facial skin, otherwise yellow or yellow-green, turns turquoise. The iris changes in color between yellow, red or brown seasonally. The young hatch naked, but soon grow white or tan down.[Myers et al. 2009]
Darter vocalizations include a clicking or rattling when flying or perching. In the nesting colonies, adults communicate with croaks, grunts or rattles. During breeding, adults sometimes give a caw or sighing or hissing calls. communicate with squealing or squawking calls.
Distribution and ecology
Darters are mostly
tropical in distribution, ranging into
subtropical and barely into warm
temperate regions. They typically inhabit
fresh water lakes, rivers, marshes, swamps, and are less often found along the seashore in
brackish water estuaries, bays,
and
mangrove. Most are sedentary and do not
bird migration; the populations in the coolest parts of the range may migrate however. Their preferred mode of
bird flight is soaring and
gliding; in
flapping flight they are rather cumbersome. On dry land, darters walk with a high-stepped gait, wings often spread for balance, just like
do. They tend to gather in flocks – sometimes up to about 100 birds – and frequently associate with
,
or
, but are highly territorial on the nest: despite being a colonial nester, breeding pairs – especially males – will stab at any other bird that ventures within reach of their long neck and bill. The
Oriental darter (
A. melanogaster sensu stricto) is a
Near Threatened species. Habitat destruction along with other human interferences (such as egg collection and
pesticide overuse) are the main reasons for declining darter populations.
Diet
Darters feed mainly on mid-sized
fish;
[E.g. Centrarchidae (sunfishes), Cichlidae (cichlids), Cyprinidae (carps, minnows and relatives), Cyprinodontidae (pupfishes), Mugilidae (mullets), Plotosidae (eeltail catfishes) and Poeciliidae (livebearers): Myers et al. 2009] far more rarely, they eat other
Aquatic animal [E.g. Anura (frogs and toads), Caudata (newts and salamanders), , and even baby : Myers et al. 2009] and large
[E.g. Crustacea (crabs, crayfish and shrimps), , and : Myers et al. 2009] of comparable size. These birds are foot-propelled divers which quietly stalk and ambush their prey; then they use their sharply pointed
beak to impale the food animal. They do not dive deep but make use of their low buoyancy made possible by wettable plumage, small air sacs and denser bones.
On the underside of the cervical vertebrae 5–7 is a keel, which allows for
to attach to form a
hinge-like mechanism that can project the neck, head and bill forward like a
throwing spear. After they have stabbed the prey, they return to the surface where they toss their food into the air and catch it again, so that they can swallow it head-first. Like
, they have a vestigial
preen gland and their plumage gets wet during diving. To dry their feathers after diving, darters move to a safe location and spread their wings.
Darters go through a synchronous
moult of all their primaries and secondaries making them temporarily flightless, although it is possible that some individuals go through incomplete moults.
Predation
of darters are mainly large
carnivorous birds, including
passerines like the
Australian raven (
Corvus coronoides) and
house crow (
Corvus splendens), and birds of prey such as
(
Circus aeruginosus complex) or Pallas's fish eagle (
Haliaeetus leucoryphus). Predation by
Crocodylus has also been noted. But many would-be predators know better than to try to catch a darter. The long neck and pointed bill in combination with the "darting" mechanism make the birds dangerous even to larger carnivorous
, and they will actually move toward an intruder to attack rather than defending passively or fleeing.
[Kennedy et al. (1996), Myers et al. 2009]
Breeding
They usually breed in colonies, occasionally mixed with
or herons. The darters
pair bond monogamously at least for a breeding season. There are many different types of displays used for mating. Males display to attract females by raising (but not stretching) their wings to wave them in an alternating fashion, bowing and snapping the bill, or giving twigs to potential mates. To strengthen the pair bond, partners rub their bills or wave, point upwards or bow their necks in unison. When one partner comes to relieve the other at the nest, males and females use the same display the male employs during courtship; during changeovers, the birds may also "
yawn" at each other.
Breeding is seasonal (peaking in March/April) at the northern end of their range; elsewhere they can be found breeding all year round. The bird nest are made of twigs and lined with leaves; they are built in trees or reeds, usually near water. Typically, the male gathers nesting material and brings it to the female, which does most of the actual construction work. Nest construction takes only a few days (about three at most), and the pairs copulate at the nest site. The clutch size is two to six bird egg (usually about four) which have a pale green color. The eggs are laid within 24–48 hours and Avian incubation for 25 to 30 days, starting after the first has been laid; they hatch asynchronously. To provide warmth to the eggs, the parents will cover them with their large webbed feet, because like their relatives they lack a brood patch. The last young to hatch will usually starve in years with little food available. Bi-parental care is given and the young are considered altricial. They are fed by regurgitation of partly digested food when young, switching to entire food items as they grow older. After fledging, the young are fed for about two more weeks while they learn to hunt for themselves.[Answers.com 2009, Myers et al. 2009]
These birds reach sexual maturity by about two years, and generally live to around nine years. The maximum possible lifespan of darters seems to be about sixteen years.[AnAge 2009, Myers et al. 2009]
Darter eggs are edible and considered delicious by some; they are locally collected by humans as food. The adults are also eaten occasionally, as they are rather meaty birds (comparable to a domestic duck); like other fish-eating birds such as cormorants or they do not taste particularly good though. Darter eggs and are also collected in a few places to raise the young. Sometimes this is done for food, but some in Assam and Bengal train tame darters to be employed as in cormorant fishing. With an increasing number of nomads settling down in recent decades, this cultural heritage is in danger of being lost. On the other hand, as evidenced by the etymology of "anhinga" detailed below, the Tupi people seem to have considered the anhinga a kind of bird of ill omen.
Systematics and evolution
The
genus Anhinga was introduced by the French zoologist Mathurin Jacques Brisson in 1760, with the
anhinga or American darter (
Anhinga anhinga) as the
type species.
is derived from the Tupi
ajíŋa (also transcribed
áyinga or
ayingá), which in local
mythology refers to a malevolent
forest spirit; it is often translated as "devil bird". The name changed to
anhingá or
anhangá as it was transferred to the Tupi–Portuguese Língua Geral. However, in its first documented use as an English term in 1818, it referred to an
Old World darter. Ever since, it has also been used for the modern genus
Anhinga as a whole.
[Jobling (1991): p.48, MW 2009]
This family is very closely related to the other families in the suborder Sulae, i.e. the Phalacrocoracidae (cormorants and shags) and the Sulidae (gannets and boobies). Cormorants and darters are extremely similar as regards their body and leg and may be sister taxa. In fact, several darter were initially believed to be cormorants or shags (see below). Some earlier authors included the darters in the Phalacrocoracidae as subfamily Anhingina, but this is nowadays generally considered overlumping. However, as this agrees quite well with the fossil evidence,[E.g. genera like Borvocarbo, Limicorallus or Piscator: Mayr (2009): pp.65–67] some unite the Anhingidae and Phalacrocoracidae in a Taxonomic rank Phalacrocoracoidea.[Brodkorb & Mourer-Chauviré (1982), Olson (1985): p.207, Becker (1986), Christidis & Boles (2008): p.100, Mayr (2009): pp.67–70, Myers et al. 2009]
The Sulae are also united by their characteristic display behavior, which agrees with the phylogeny as laid out by anatomical and DNA sequence data. While the darters' lack of many display behaviors is shared with gannets (and that of a few with cormorants), these are all that are absent in , and also. Like cormorants but unlike other birds, darters use their hyoid bone to stretch the gular sac in display. Whether the pointing display of mates is another synapomorphy of darters and cormorants that was dropped again in some of the latter, or whether it evolved independently in darters and those cormorants that do it, is not clear. The male raised-wing display seems to be a synapomorphy of the Sulae; like almost all cormorants and shags but unlike almost all gannets and boobies, darters keep their bent as they lift the wings in display, but their alternating wing-waving, which they also show before take-off, is unique. That they often balance with their outstretched wings during walking is probably an of darters, necessitated by their being plumper than the other Sulae.[Kennedy et al. (1996)]
The Sulae were traditionally included in the Pelecaniformes, then a paraphyletic group of "". The supposed traits uniting them, like all-webbed toes and a bare gular sac, are now known to be convergent, and pelicans are apparently closer relatives of than of the Sulae. Hence, the Sulae and the frigatebirds – and some prehistoric relatives – are increasingly separated as the Suliformes, which is sometimes dubbed "Phalacrocoraciformes".[Christidis & Boles (2008): p.100, Answers.com 2009, Mayr (2009): pp.67–70, Myers et al. 2009]
Living species
There are four living species of darters recognized, all in the
genus Anhinga,
although the Old World ones were often lumped together as subspecies of
A. melanogaster. They may form a
superspecies with regard to the more distinct anhinga:
[Olson (1985): p.207, Becker (1986)]
Extinct "darters" from Mauritius and Australia known only from bones were described as Anhinga nana ("Mauritian darter") and Anhinga parva. But these are actually misidentified bones of the long-tailed cormorant ( Microcarbo/Phalacrocorax africanus) and the little pied cormorant ( M./P. melanoleucos), respectively. In the former case, however, the remains are larger than those of the geographically closest extant population of long-tailed cormorants on Madagascar: they thus might belong to an extinct subspecies (Mauritian cormorant), which would have to be called Microcarbo africanus nanus (or Phalacrocorax a. nanus) – quite ironically, as the Latin term nanus means dwarf. The Late Pleistocene Anhinga laticeps is not specifically distinct from the Australasian darter; it might have been a large paleosubspecies of the last ice age.[Miller (1966), Olson (1975), Brodkorb & Mourer-Chauviré (1982), Olson (1985): p.206, Mackness (1995)]
Fossil record
The
fossil record of the Anhingidae is rather dense, but very
already and appears to be lacking its base. The other families placed in the Phalacrocoraciformes sequentially appear throughout the
Eocene, the most distinct – frigatebirds – being known since almost 50 Ma (million years ago) and probably of
Paleocene origin. With fossil gannets being known since the mid-Eocene (c. 40 Ma) and fossil cormorants appearing soon thereafter, the origin of the darters as a distinct lineage was presumably around 50–40 Ma, maybe a bit earlier.
[Becker (1986), Mayr (2009): pp.67–70]
Fossil Anhingidae are known since the Early Miocene; a number of prehistoric darters similar to those still alive have been described, as well as some more distinct genera now extinct. The diversity was highest in South America, and thus it is likely that the family originated there. Some of the genera which ultimately became extinct were very large, and a tendency to become flightless birds has been noted in prehistoric darters. Their distinctness has been doubted, but this was due to the supposed "Anhinga" fraileyi being rather similar to Macranhinga, rather than due to them resembling the living species:[Cione et al. (2000), Alvarenga & Guilherme (2003)]
-
Meganhinga Alvarenga, 1995 (Early Miocene of Chile)
-
"Paranavis" (Middle/Late Miocene of Paraná, Argentina) – a nomen nudum
[Named in a thesis and hence not validly according to ICZN rules. An apparently flightless species the size of A. anhinga: Noriega (1994), Cione et al. (2000)]
-
Macranhinga Noriega, 1992 (Middle/Late Miocene – Late Miocene/Early Pliocene of SC South America) – may include "Anhinga" fraileyi
-
Giganhinga Rinderknecht & Noriega, 2002 (Late Pliocene/Early Pleistocene of Uruguay)
- Anhinga
Prehistoric members of
Anhinga were presumably distributed in similar
as today, ranging into
Europe in the hotter and wetter
Miocene. With their considerable stamina and continent-wide distribution abilities (as evidenced by the anhinga and the Old World
superspecies), the smaller lineage has survived for over 20 Ma. As evidenced by the fossil species'
biogeography centered around the
equator, with the younger species ranging eastwards out of the Americas, the
Hadley cell seems to have been the main driver of the genus' success and survival:
[Olson (1985): p.206]
-
Anhinga walterbolesi Worthy, 2012 (Late Oligocene to Early Miocene of central Australia
-
Anhinga subvolans (Brodkorb, 1956) (Early Miocene of Thomas Farm, US) – formerly in Phalacrocorax
[UF 4500, a proximal right humerus half. About 15% larger than A. anhinga and more : Brodkorb (1956), Becker (1986)]
-
Anhinga cf. grandis (Middle Miocene of Colombia –? Late Pliocene of SC South America)
[Including a distal right humerus (UFAC-4721) from the Solimões Formation of Cachoeira do Bandeira (Acre, Brazil). Size identical to A. grandis, but distinctness in space and time makes assignment to that species questionable: Mackness (1995), Alvarenga & Guilherme (2003)]
-
Anhinga sp. (Sajóvölgyi Middle Miocene of Mátraszõlõs, Hungary) – A. pannonica?
[An ungual phalanx bones: Gál et al. (1998–99), Mlíkovský (2002): p.74]
-
"Anhinga" fraileyi Campbell, 1996 (Late Miocene –? Early Pliocene of SC South America) – may belong in Macranhinga
[Holotype LACM 135356 is a slightly damaged right tarsometatarsus; other material includes a distal left ulna end (LACM 135361), a well-preserved left tibiotarsus (LACM 135357), two cervical vertebrae (LACM 135357-135358), three humerus pieces (LACM 135360, 135362-135363), probably also the almost complete left humerus UFAC-4562. A rather short-winged species about two-thirds larger than A. anhinga; apparently distinct from the living genus: Campbell (1992), Alvarenga & Guilherme (2003)]
-
Anhinga pannonica Lambrecht, 1916 (Late Miocene of C Europe ?and Tunisia, East Africa, Pakistan and Thailand –? Sahabi Early Pliocene of Libya)
[a cervical vertebra (the holotype) and a carpometacarpus; additional material includes another cervical vertebra and femur, humerus, tarsometatarsus and tibiotarsus pieces. About as large as A. rufa, apparently ancestral to the Old World lineages: Martin & Mengel (1975), Brodkorb & Mourer-Chauviré (1982), Olson (1985): p.206, Becker (1986), Mackness (1995), Mlíkovský (2002): p.73]
-
Anhinga minuta Alvarenga & Guilherme, 2003 (Solimões Late Miocene/Early Pliocene of SC South America)
[UFAC-4720 (holotype, an almost complete left tibiotarsus) and UFAC-4719 (almost complete left humerus). The smallest known darter (30% smaller than A. anhinga), probably not very closely related to any living species: Alvarenga & Guilherme (2003)]
-
Anhinga grandis Martin & Mengel, 1975 (Late Miocene –? Late Pliocene of US)
[Assorted material, including the holotype UNSM 20070 (a distal humerus end) and UF 25739 (another humerus piece). Longer-winged, about 25% larger than and twice as heavy as A. anhinga, but apparently a close relative: Martin & Mengel (1975), Olson (1985): p.206, Becker (1986), Campbell (1992)]
-
Anhinga malagurala Mackness, 1995 (Allingham Early Pliocene of Charters Towers, Australia)
[QM F25776 (holotype, right carpometacarpus) and QM FF2365 (right proximal femur piece). Slightly smaller than A. melanogaster and apparently quite distinct: Becker (1986), Mackness (1995)]
-
Anhinga sp. (Early Pliocene of Bone Valley, US) – A. beckeri?
[Ulna fossils larger than A. anhinga: Becker (1986)]
-
Anhinga hadarensis Brodkorb & Mourer-Chauviré, 1982 (Late Pliocene/Early Pleistocene of E Africa)
[The holotype is a well-preserved left femur (AL 288-52). Additional material consists of a proximal left femur (AL 305-2), a distal left tibiotarsus (L 193-78), a proximal (AL 225-3) and a distal (11 234) left ulna, a proximal left carpometacarpus (W 731), and well-preserved (10 736) and fragmentary (2870) right . Slightly smaller than A. rufa and probably its direct ancestor: Brodkorb & Mourer-Chauviré (1982), Olson (1985): p.206]
-
Anhinga beckeri Emslie, 1998 (Early – Late Pleistocene of SE US)
Protoplotus, a small Paleogene phalacrocoraciform from Sumatra, was in old times considered a primitive darter. However, it is also placed in its own family (Protoplotidae) and might be a basal member of the Sulae and/or close to the common ancestor of cormorants and darters.[Olson (1985): p.206, Mackness (1995), Mayr (2009): pp.62–63]
Citations
General and cited sources
-
AnAge 2009: Anhinga longevity data. Retrieved 2009-SEP-09.
-
Answers.com 2009: darter. In: Columbia Electronic Encyclopedia (6th ed.). Columbia University Press. Retrieved 2009-Sep-09.
-
Christidis, Les & Boles, Walter E. (2008): Systematics and Taxonomy of Australian Birds. CSIRO Publishing, CollingwoodVictoria, Australia.
-
Cione, Alberto Luis; de las Mercedes Azpelicueta, María; Bond, Mariano; Carlini, Alfredo A.; Casciotta, Jorge R.; Cozzuol, Mario Alberto; de la Fuente, Marcelo; Gasparini, Zulma; Goin, Francisco J.; Noriega, Jorge; Scillatoyané, Gustavo J.; Soibelzon, Leopoldo; Tonni, Eduardo Pedro; Verzi, Diego & Guiomar Vucetich, María (2000): Miocene vertebrates from Entre Ríos province, eastern Argentina. English In: Aceñolaza, F.G. & Herbst, R. (eds.): El Neógeno de Argentina. INSUGEO Serie Correlación Geológica 14: 191–237.
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Jobling, James A. (1991): A Dictionary of Scientific Bird Names. Oxford University Press, Oxford, UK.
-
Mayr, Gerald (2009): Paleogene Fossil Birds. Springer-Verlag, Heidelberg & New York.
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Merriam-Webster (MW) 2009: Online English Dictionary – Anhinga. Retrieved 2009-Sep-09.
-
Mlíkovský, Jirí (2002): Cenozoic Birds of the World (Part 1: Europe). Ninox Press, Prague.
-
Myers, P.; Espinosa, R.; Parr, C.S.; Jones, T.; Hammond, G.S. & Dewey, T.A. 2009: Animal Diversity Web – Anhingidae. Retrieved 2009-Sep-09.
-
Noriega, Jorge Ignacio (1994): Las Aves del "Mesopotamiense" de la provincia de Entre Ríos, Argentina "The. Doctoral thesis, Universidad Nacional de La Plata in. PDF abstract
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External links
