The maguari stork (Ciconia maguari) is a large species of stork that inhabits seasonal wetlands over much of South America, and is very similar in appearance to the white stork; albeit slightly larger.King CE. 1988. An ethological comparison of three storks: Ciconia boyciana, C. ciconia, and C. maguari. MS Thesis, Oklahoma State University, Stillwater, Oklahoma. It is the only species of its genus to occur in the New WorldShort LL. 1975. A zoogeographic analysis of the South American Chaco avifauna. Bulletin of the American Museum of Natural History 154: 163-352. and is one of the only three New World stork species, together with the wood stork and the jabiru.Thomas BT. 1985. Coexistence and behaviour differences among three western hemisphere stork species. Ornithological Monographs 36: 921-931.
Taxonomy The maguari stork was formally described in 1789 by the German naturalist Johann Friedrich Gmelin in his revised and expanded edition of Carl Linnaeus's Systema Naturae. He placed it with the herons, cranes and storks in the genus Ardea and coined the binomial name Ardea maguari. Gmelin's description was ultimately based on the "Maguari Brasiliensibus" that had been described and illustrated in 1648 by the German naturalist Georg Marcgrave in his book Historia Naturalis Brasiliae. The maguari stork is now one of seven storks placed in the genus Ciconia that was introduced in 1760 by the French zoologist Mathurin Jacques Brisson. The genus name is the Latin word for "stork". The specific epithet maguari and the common name are from the Tupi language, "Maguarí" or "Baguarí" means "heavy bill". The species is monotypic: no subspecies are recognised.
This stork was formerly placed in its own genus Euxenura, but was later reclassified as belonging to Ciconia because of its strong morphological and ethological similarity to other storks of this genus.Kahl MP. 1972. Comparative ethology of the Ciconiidae. Part 4. The "typical" storks (genera Ciconia, Sphenorhyncus, Dissoura, and Euxenura). Zeitschrift für Tierpsychologie 30: 225-252. However, the maguari stork most closely resembles both the white stork and the Oriental stork in morphology and behaviour; and strongly resembles the white stork in its manner of performing the up-down greeting display. Plumage pattern and soft part colourations are also very similar between these three stork species. Further, phylogenetic analyses based on a portion of the cytochrome b oxidase gene have suggested that the maguari stork is evolutionarily paired with the white stork-Oriental stork sister group; although the morphological similarity between the maguari stork and the Oriental stork has been considered to be greater than between the white stork and the Oriental stork. Incidentally, the maguari stork also shares the prominent forkedness of its tail with the woolly-necked stork (Ciconia episcopus).Hancock JA, Kushlan JA, Kahl MP. 1992. Storks, Ibises and Spoonbills of the World. Academic Press.
Fossils of the extinct Pleistocene stork Ciconia maltha discovered in North America appear to be morphologically intermediate between the maguari stork and white stork and may therefore represent a common ancestral link between these two species that inhabit different continents.Howard H. 1942. A review of the American fossil storks. Carnegie Institution of Washington Publication 530: 187-203. Ciconia maltha was probably highly dispersive and could have extended its range to Venezuela from North America during the Pliocene,Walsh S, Sanchez L & R, Urumaco. 2008. The first Cenozoic fossil bird from Venezuela. Paläontologische Zeitschrift 82: 105-112. part of the range of the extant maguari stork.
Description
Adult appearance The bird stands at tall and has a wingspan of around , making it similar in size to the congeneric white stork. Nine male maguari storks weighed an average of while five females weighed an average of . It is intermediate in size between the smaller wood stork and the larger jabiru, the two other stork species with which the maguari stork exists in sympatry in some parts of its range. Much of the adult plumage is white, with black flight feathers and a forked blacked tail which is shorter than the stiff white under-tail coverts, so that these protrude from underneath the tail and may function aerodynamically in flight. The forked tail clearly distinguishes the maguari stork from the white stork, and is easily observed in flight from the ground thanks to the white under-tail coverts.Wetmore A. 1926. Observations on the birds of Argentina, Paraguay, Uruguay, and Chile. United States National Museum Bulletin 133: 1-448. During flight, this stork offers an impressive sight. It soars at least a hundred metres above the ground with an outstretched neck and extended legs, intermittently beating its broad wings to gain momentum for long glides. It flaps its wings at a rate of 181 beats per minuteKahl MP. 1971. Flapping rates of storks in level flight. The Auk 88: 428. and the wingspan measures 150–180 cm.Oiseaux-birds. Accessed 19/06/16. http://www.oiseaux-birds.com/card-maguari-stork.html. This stork needs to make three long jumps before it can take off from the ground.Hudson WH. 1920. Birds of La Plata, Volume 2. J.M. Dent and Sons Ltd., New York.
Individuals undergo a fresh moult in the breeding season to produce brighter plumage in preparation for courtship. Head and neck feathers consist of long semi-plumes measuring up to 18 cm long that become erectile and are important in courtships and aggressive displays. Barbs on the neck feathers also have no barbules, thus making the neck appear like a translucent net.
The bill is straight, bluish grey, and lined with red. The final third portion along the bill length is dark maroon. The iris is lemon-yellow or cream white and the legs are purplish red. The skin of the throat and the pebbly-textured lores are orangey red, becoming deeper red during courtship. The sexes are largely indistinguishable externally, except that the male is slightly larger with a slightly upward curved bill. Individuals usually weigh 3800-4200 g, with males being heavier.
Juvenile appearance A distinct characteristic unique to this stork species is intermediately dark plumage in the young, which persists for most of the nestling period. In the chicks' first few days after hatching, their sparse down is snowy white. The chicks subsequently undergo two basic moults before entering adulthood. The first moult usually begins after four days, in which black semi-plumes on the head and neck begin to emerge; followed shortly by the emergence of greyish-black down feathers over the body after one week of age. Some white down feathers initially remain attached to give a temporary mottled black and white appearance before finally receding to leave a darkish grey downy plumage. During development of the dark down, the bill, legs and feet are shiny black. A pale yellow stripe extends up the venter, the gular pouch is bright orange, and the iris is dark brown. At hatching, nestlings weigh 76-90g.
After the chicks pass their third week of age, the black down develops olive streaks and the only parts of the body that do not appear dark are the bright orange gular skin and a small patch of white down above and below the tail. Just over 10 days later, black flight feathers develop, shortly followed by black contour feathers. At this point, the chicks are fledged and have their first full juvenile plumage after about a month of hatching. Hence, juveniles remain black at fledging, by which time the orange of the gular pouch has also turned pale scarlet.
In the second moult, white down begins to return when the chicks are seven weeks old, followed by white semi-plumes then white contour feathers. The first white basic plumage is complete after three months and resembles that of adults. By this time, the legs and feet are now an incipient pink and the bill has become bicoloured (pale blue and maroon). Although the young now resemble adults, the skin surrounding the eye remains black for about a year before turning red, and the dark brown iris does not begin to yellow until after two years old. These are two potentially useful features that identify juvenile maguari storks; but in the field, the dark iris of the juveniles is the most reliable feature that distinguishes them from adults.
Two hypotheses have been proposed to explain the dark colouration in the juveniles. First, the blackish feathers may serve as camouflage against both ground and aerial predators. Alternatively, the black plumage may serve a thermoregulatory function by enhancing its absorption of the sun's radiation.Cowles RB, Hamilton WJ, Heppner F. 1967. Black pigmentation: adaptation for concealment or heat conservation? Science 158: 1340-1341. This could arguably be advantageous because this stork breeds during the winter in the part of its range in the southern hemisphere, so that the chicks can be exposed to low environmental temperatures. However, Thomas regards the anti-predator explanation for the dark plumage to be more plausible.
Vocalisations Adults utter wheezing, hissing, disyllabic whistles during up-down greeting displays at the nests about every 1–1.5 seconds. These whistles are slower and lower pitched than the corresponding vocalisations of other Ciconia, but sound similar to those of the Abdim's stork and the woolly-necked stork. The quality of these vocalisations is probably linked with the maguari stork's ground nesting habits and may be an adaptation to minimise attraction of predators' attention. Young make begging calls that have been described as Ehehe-ehehe.
Distribution and habitat The maguari stork has a relatively wide distribution over much of South America, and occurs primarily to the east of the Andes. It lives in the Llanos of Venezuela and eastern Colombia; Guyana; eastern Bolivia; Paraguay; Brazil, but rarely in the Amazon and the north-east,Tavares DC, Siciliano S. 2013. Notes on records of Ciconia maguari (Gmelin, 1789)(Aves, Ciconiidae) on northern Rio de Janeiro State, Southeast Brazil. Pan-American Journal of Aquatic Sciences 8: 352-357.); Uruguay and Argentina. The most southerly part of the range lies in the Chubut province. It more rarely occurs to the west of the Andes (e.g. in Chile) and probably does not breed there.Johnson AW. 1965. The Birds of Chile and Adjacent Regions of Argentina, Bolivia and Peru, volume I. Platt Establecimientos Graficos, Buenos Aires, Argentina. It is a rare visitor to the Suriname coast from March until MaySpaans AL. 1975. The status of the wood stork, jabiru and maguari stork along the Surinam coast, South America. Ardea 63: 116-130. and also been reported as a vagrant on Trinidad and Tobago.
It is especially common and widespread in the Chaco of Argentina, which appears to be a popular destination for flocks of about 30-40 migrant individuals from the southern hemisphere part of the range that come from the south in winter to seek warmer temperatures. The stork is also common in Brazil, especially in the state Rio Grande do Sul, ParaguayLuthin CS. 1987. Status of and conservation priorities for the world's stork species. Colonial Waterbirds 10: 181-202. and the Pampas of Argentina. It occurs seasonally and is common in the Pantanal of Argentina. Large numbers migrate to the Pantanal in the wet season, probably from the Parana Basin and Rio Grand do Sul.Antas PTZ. 1994. Migration and other movements among the lower Parana River valley wetlands, Argentina, and the south Brazil/Pantanal wetlands. Bird Conservation International 4: 181-190. However, overall migration patterns for this species across its range have thus far not been determined exactly.