Plumbeous ibis
Plumbeous ibis | |
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Scientific classification![]() | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Aves |
Order: | Pelecaniformes |
Family: | Threskiornithidae |
Genus: | Theristicus |
Species: | T. caerulescens
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Binomial name | |
Theristicus caerulescens (Vieillot,1817)
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Current resident extant range according to the IUCN 2012 |
Theplumbeous ibis(Theristicus caerulescens), also formerly called the blue ibis,[2]is a large distinctiveibisspecies endemic to parts of centralSouth America.
Taxonomy and systematics
[edit]The plumbeous ibis has historically undergone frequent reclassification and been placed in various genera such asMolydophanes,Geronticus,TheresticusandHarpiprion.[3][4]It has also been referred to asIbis caerulescens[5]andTheresticus(Harpiprion)caerulescens.[6]Nevertheless, this ibis has traditionally been assigned to the monotypic genusHarpiprion,carrying the binomial nameHarpiprion caerulescens;[4]on the basis that this species was previously believed to have no close relatives.[7]However,phylogenetic analysesbased on both nuclear and mitochondrial DNA markers have suggested that the plumbeous ibis is closely related to other ibis species in the genusTheresticussuch as thebuff-necked ibis;given the markedly low genetic distances between the plumbeous ibis and otherTheresticusspecies.[8]Hence, the current placement of the plumbeous ibis in the genusTheresticusappears justified.[1]
Description
[edit]Appearance
[edit]This large ibis measures 71–77 cm in length,[4]with a wing length of 397-450mm in males and 360-406mm in females.[9]Theculmenlength is 145-167mm in males, and 126-147mm in females.[9]The sexes are similar in appearance, but the female is slightly smaller.[4]The plumbeous ibis is easily recognisable through a distinctive shaggycrestcomprising long grey plumes that extend from the back of head 10 cm down the nape.[6]A prominent, narrow, white feathered band also extends around the forehead, which has earned this species the German common nameStirnbandibis(headband ibis). Overall, it is readily distinguishable in the field from other ibises by its solid colouration and thick neck.[4]The plumbeous ibis is the mostmorphologicallysimilar to thesympatricbuff-necked ibisTheresticus caudatus,but differs in colouration and neck structure.[4]
The adultplumageis usually grey; but can be bluish grey,[4]greenish grey[10]or brownish grey.[6]The dorsal feathers are mottled greyish-brown, so that the plumage appears lighter below than above.[4]The flight and tail feathers are dark brown or black, superimposed with a glossy greenish bronze.[4]It has also been reported as having various other subtle tinges on the body depending on the light. When the bird is seen in the correct light, Hudson[2]has described the plumage as appearing silvery grey, the top of the head as dark brown with a greenish tinge, the primary feathers as dark blue, the tail as dark green, and the feathers of the throat and neck as light brown with an occasional pinkish tinge.
The black, downward-curved bill is serrated between themandibles.The bare skin of theloresand throat is black or dark grey.[4]The legs are a pinkish orange,[4][6]darkening in the breeding season in preparation for courtship.[4]The iris is deep orange, but has been noted to be slightly paler around the pupil.[5]In some individuals, the iris has also been reported to be brownish yellow.[6]
The chicks have light grey downy plumage that lacks the more sophisticated tinges in adults.[10]Fledged young are also distinguishable from adults by a dark iris, grey legs, a less developed nuchal crest, a more extensive white band on the forehead[10][11]and red bare skin patches.[11]The white band on the forehead begins to develop in the young after 18 days of age and up close appears a brighter white than that of adults.[10]
Through its powerful musculature, this ibis is sturdy and direct in flight; stretching out its neck and wings and steadily beating its wings with intermittent gliding.[4][5]
Vocalisations
[edit]The loudvocalisationsuttered by this species are diverse. The basic call is a high-pitched, rapidpi-pi-pi-pi[6]which has a somewhat metallic timbre and can be uttered when the bird stands on the ground during daytime.[2]This call has been said to resemble the sound of abanjo with brass strings so big that it could be heard a mile and a half away.[2]
This ibis also makes a slow but energetic trumpetingflight callthat has been transcribed askree kreee kree[5]ork k kuh kuh KEE KEE KEE KEE KEE KEE KEE keh kuh kuh.[6]While making flight calls, it glides through the air with motionless downward curved wings.[5]It also utters a nasal, high-pitched, rapid series of cackles when perched on branches or at the nest site transcribed astututututu;[12]sometimes interspersed with elements of ti-ti[13]and often in duet between mates large distances apart.[12][14]Another contact call is made between foraging mates and has been transcribed as a cacklingkuk-kuk…kuk-kuk…kuk kuk.[13]Overall, the broad range of loud distinctive calls of this species indicates the importance of long-range communication between individuals, especially mates.[14]
Distribution and habitat
[edit]The plumbeous ibis has a relatively narrow range that extends through parts of central South America. It occurs in south-westernBrazil,especially in southernMato Grosso[15]andRio Grande do Sul;[6]Paraguay, especially in theChaco[16]and in the Paraguayan section of theParana Basin;[17]Uruguay;north-easternArgentinaand northern and easternBolivia.The northern Bolivian population is geographically isolated from the larger continuous population spanning the remaining part of this ibis's range.[1]The westernmost part of its range extends into theAndeanfoothills in central Bolivia andTucuman.[7]In Argentina, it has been occasionally sighted as far south as theCordobaandBuenos Airesprovinces; but is non-native in these regions.[4]
Although this species appears to be relatively common, it is patchily distributed throughout its global range; being relatively abundant in some regions but less so in others.[4]For example, it is endemic but actually uncommon in Rio Grande do Sul, but frequently occurs in the northernLagoa dos Patos.[6]It is relatively common in the Chaco of Paraguay,[5][16]especially in the northern Chaco where large numbers of individuals occur throughout the expanses of freshwater, so that this species is considered emblematic of the wetland avifauna of this region.[18]Conversely, it has rarely been recorded in the pampas of northern Argentina in the southernmost part of its distribution; with an occasional handful of individuals at a time having been sighted during surveys throughout the 1990s in theLaguna MelincueRamsar Site in the southernSanta Fe Province.[19]
Its habitat largely comprises the lowland grassy wetlands of thePantanaland the Chaco. It is found here foraging at marshes, swamps, lagoons, shallow lakes, flooded pastures, ponds and other moist ground; but also perches in tree branches near or above the water to roost. It has also been sighted in upland marshes,[6]usually up to 600m in elevation;[13]and at small remnant pools in desiccated lagoons and on dry grasslands.[4][5][6]Further, this ibis commonly occurs near human habitation and other manmade features;[4]including dams[20]and seasonally-flooded rice fields.[21]It is also a relatively common sight along theTranspantaneira Highwayin the Pantanal of Mato Grosso.[22]Finally, it has been recorded close to the east Brazilian coast in wet areas in theLagoa do Peixe National Parkon the peninsula separating Lagoa dos Patos from the Atlantic (Pereira & Poerschke, 2009); but probably avoids the saline and brackish waters.
Individuals are usually sedentary and can remain in a specific area all year round.[4]They have however been reported to migrate on a local scale.[2]Circumstantial evidence from the novel presence of individuals atIncachaca Lakein theChapare Provinceof Bolivia suggests that this species may migrate between the geographically separated northern Bolivian and other South American populations, and may use Incachaca as a resting place en route.[20]Since no subspecies have been noted for this species,[20]the world population is probably kept genetically homogenous by short migrations of individuals between the two geographically separated subpopulations. However, it remains unknown whether this species has regular migration patterns.[2]Incidentally, the species’ discovery at Lake Incachaca was its first recorded occurrence in thecloud forestecoregionand was also a new altitudinal record.[20]
Unlike other ibis species, the plumbeous ibis does not form large intraspecific flocks.[4]It is most often seen singly or in pairs,[6]but is also more rarely seen in groups of up to six individuals.[2][4]The larger groups appear to consist of two mates accompanied by their fledged juveniles.[4]
Ecology and behaviour
[edit]Feeding
[edit]This ibis's diet comprises aquatic invertebrates; snails,[6]especiallyapple snailsof the genusPomacea;[23]mussels;[24]crabs;[16]frogs; fish and eels.[2]It has also been reported to eat snakes,[25]lizards, skinks and terrestrial invertebrates;[26]which is plausible given its occasional occurrence in dry grasslands.[4][6]Despite this ibis's apparently generalist diet, it is found to specialise on molluscs in the Paraguay-Parana basin.[17]
The plumbeous ibis often feeds solitarily or in pairs,[27]but may assemble in loose flocks to forage in winter when food is scarcer.[13]Individuals have also been found foraging together withwhite-faced ibisesandjacanas.[15]The plumbeous ibis's typical foraging strategy consists in walking slowly through shallow mud and water, probing fast and repeatedly with its bill in the water in search of prey.[4][13]Its bill is sometimes completely submerged in the water[5]and its aquatic foraging habits ecologically distinguishes it from the related, sympatric buff-necked ibis which preferentially forages in adjacent dry grassland;[10]although the breeding biology of these two species is regarded to be similar.[10]
Both parents feed the young by regurgitation.[13]Chicks induce the parent to feed them by prodding their bills into the gap between the upper and lower mandibles of the parent's bill. Thereupon, the parent regurgitates food for the nestlings with head movements during which the young hang onto the parent with their bills and sway passively with such movements.[10]With age, the juveniles become more independent in food acquisition as they begin to leave the nest, and are fed less frequently.[10]
Breeding
[edit]Unlike many other ibises, the plumbeous ibis is a non-colonial breeder.[22]Breeding occurs in sparsely wooded areas[10]from March until mid-October.[10][11]Nest building by both partners begins in March[10]and takes about a month to complete.[11]Nests are commonly constructed above or near to water on horizontal limbs of massive fig trees ofFicusspecies.[11][22]or in the speciesLuehea paniculata.[10]Some nests in Mato Grosso in Brazil have been found situated in trees above or near to farmsteads,[10][15]which may further reflect this species’ association with humans. The nest typically measures 25 cm in height and 50 cm in width[11]and consists of a loose, disorderly constructed platform of dry branches or sticks,[15]with a hollow about 20 cm deep lined with dry grass and leaves;[10][11]therefore resembling that of the wood stork.[22]Both partners contribute to building the nest, which takes about a month to complete[11]and is situated 10-12m above the ground;[10][15]although some nests built in large fig trees in forested areas in the Pantanal may lie up to 20m above the ground.[22]The same nest may also be used by a pair over consecutive years.[10]
Copulationbetween mates takes place in April, which is shortly preceded by a relatively simplecourtship.[15]During courtship, one individual (male or female) stands on the branch of a dead tree and utters its distinctive metallic-sounding call to summon its mate, which flies onto the branch to join its partner. Thereupon, both mates prod their bills into the tree bark before the male buries his bill in the female's plumage. The male subsequently steps onto the female's back to copulate.[15]
A typicalclutchconsists of 2-3 eggs, which are pale greenish-grey[4][10]and weigh 70-74g.[11][28]Average egg dimensions have been reported as 68.6 x 44.9mm.[28]Some nests have also been found to contain eggs together with young in various developmental stages; which suggests that this ibis may sometimes lay two consecutive clutches per year.[22]Theincubationperiod is 28 days[11]and the young usually hatch in early September.[10][11]In the chicks’ first 10 days, they are constantly guarded by one of the parents. The two parents alternately guard the nest at night, and the bird returning to the nest signals the change of nest guarding duty with a short sequence of calls and an occasional display whereby both partners prod their bills into each other's neck feathers.[10]
As the chicks age, parents attend the nest less regularly; and gradually leave the young alone for longer periods.[10]Breeding pairs usually produce two surviving young, which fledge after 40–43 days of hatching,[10][11]coinciding with the end of the dry season in the Pantanal.[10]At fledging, the young may leave the nest and begin to venture further away with age,[10]usually feeding in marshes near the nest.[11]Parents have been noted to fly onto meadows adjacent to the tree containing the nest and utter monosyllabic calls that appear to function as an invitation for the young to follow the parent to adult feeding grounds.[10]The young thenceforth feed with adults away from the nest and continue to use the nest-site tree for sleeping several weeks after fledging.[11]
Threats and survival
[edit]The plumbeous ibis is prey for multiple nest predators.[22]Although brooding parent birds are strongly aggressive toward intruders and can successfully deter small predators such asopossums,jays and vultures; they apparently lose to larger predators such ascapuchin monkeysandgreat black hawks.[22]For example, large groups of capuchins have been observed to attack plumbeous ibis nests, whereby some assailants violently force the parent bird out of the nest while others steal the eggs.[22]Brooding adults of this species also show marked aggression toward human intruders. If approached by a human, this ibis screams loudly; whereby it lowers its body, bristles its feathers and jabs its bill at the intruder.[4]Further, juveniles have been noted to defend themselves with forward lunges of the bill.[11]These defensive behaviours in this ibis reflect the bird's high predation risk and hence the adaptive value of such behaviours for survival.[4]
Like many other sympatric wading birds, it is likely threatened by habitat loss through burning and logging of nesting trees, construction and operation of hydroelectric dams in the Pantanal, and expansion of mining and agriculture.[4]This bird is however not persecuted directly.[4]
The plumbeous ibis's apparent association with humans may render it particularly vulnerable to the effects of pesticides from agriculture, especially in the Taquari Basin.[4]Additionally, pesticides together with physical disturbance to soil through agricultural machinery may reduce local availability of macroinvertebrate prey to this species (Stenert et al. 2009). One study in south Brazil has shown the plumbeous ibis to be more abundant in flooded rice fields during the post-harvest season compared to pre-harvest.[21]This may be due to the cessation of use of agrochemicals and machinery after harvest, leading to greater macroinvertebrate richness and density; so that there is greater abundance of macroinvertebrate prey for the ibis to feed on.[21]Nevertheless, this bird together with many other species still appears to be more abundant in natural wetlands than in flooded farmland.[21]Therefore, a proposed conservation strategy for this species in the face ofagricultural expansionthat may also benefit other sympatric wading birds has been to retain expanses of natural wetland within the rice cultivation ecosystem.[21]
Relationship with humans
[edit]This species is not typically hunted because it is difficult to kill and skin owing to resistance it puts up in response to being captured, and also emits an unpleasantly musty odour if caught.[5]Nevertheless, it has been kept in captivity several times.[29]For example,Berlin Zooreceived three plumbeous ibises from San Carlos Zoo, Uruguay, in 1987.[30]More recently, the plumbeous ibis has been kept in many Brazilian zoos; with one chick having successfully hatched at Brasilia Zoo in 1992.[29]
Status
[edit]The plumbeous ibis has been evaluated by theIUCNasLeast Concernsince 2004 because this species does not reach the thresholds forVulnerableunder the range size and population trend criteria.[1]The world population has been estimated at 50,000 – 100,000 individuals.[31]However, further information on the plumbeous ibis's biology is required for more successful conservation of the species, and hence safeguard it against large potential future population declines.[4]
References
[edit]![](https://upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/30px-Commons-logo.svg.png)
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- ^abcdefghHudson WH. 1920.Birds of La Plata,Volume 2. J.M. Dent and Sons Ltd., New York.
- ^Naumberg EMB. 1930. The birds of Mato Grosso, Brazil. A report on the birds secured by the Roosevelt-Rondon Expedition.Bulletin of the American Museum of Natural History60.
- ^abcdefghijklmnopqrstuvwxyzaaabacadHancock JA, Kushlan JA, Kahl MP. 1992.Storks, Ibises and Spoonbills of the World.Academic Press.
- ^abcdefghiWetmore A. 1926. Observations on the birds of Argentina, Paraguay, Uruguay, and Chile.United States National Museum Bulletin133: 1-448.
- ^abcdefghijklmnBelton W. 1984. Birds of Rio Grande do Sul, Brazil part 1. Rheidae through Furnariidae.Bulletin of the American Museum of Natural History178: 369-636.
- ^abShort LL. 1975. A zoogeographic analysis of the South American Chaco avifauna.Bulletin of the American Museum of Natural History154: 163-352.
- ^Ramirez JL, Miyaki CY, Del Lama SN. 2013.Molecular phylogeny of Threskiornithidae (Aves: Pelecaniformes) based on nuclear and mitochondrial DNA.Genetics and Molecular Research12: 2740-2750.
- ^abBlake ER. 1977.Manual of Neotropical Birds,vol I. University of Chicago Press, Chicago.
- ^abcdefghijklmnopqrstuvwxDubs B. 1988. Beobachtungen zur Fortpflanzungsbiologie des Stirnbandibis, Harpiprion caerulescens.Journal of Ornithology129: 363-365.
- ^abcdefghijklmnoCintra R. 1986. Nidificacao e crescimento do filhote de curicaca, Harpiprion caerulescens (Aves: Threskiornithidae) no Pantanal Matogrossense.Resumos XIII Congresso Brasileiro de Zoologia.Cuiba-SBZ.
- ^abVan Perlo B. 2009.A Field Guide to the Birds of Brazil.OUP USA, First Edition.
- ^abcdefOieseux birds. Accessed 26/06/16.http://www.oiseaux-birds.com/card-plumbeous-ibis.html.
- ^abRemsen JV. 1986. Aves de una localidad en la sabana humeda del norte de Bolivia.Ecologia en Bolivia8:21-35.
- ^abcdefgDubs B, 1983.Die Vögel des südichen Mato Grosso.Bern.
- ^abcStorer RW. 1989. Notes on Paraguay birds. Occasional Papers of the Museum of Zoology, the University of Michigan 719.
- ^abPor F. 1995. The Pantanal of Mato Grosso (Brazil).Monographiae Biologiae73: 77-84.
- ^Verschuren J. 1980. Saving Paraguay’s wilderness.Oryx15:465-470.
- ^Romano M, Barberis IM, Luppi M, Pagano F. 2015. Non-passerine birds from Laguna Melincue Ramsar Site, Santa Fe province, Argentina.Checklist11: 1-7.
- ^abcdTorrico-Bazoberry D. 2015. First record of Theristicus caerulescens (Aves: Threskiornithdae) in the Yungas ecoregion, new altitudinal record and new record for Cochabamba Department, Bolivia.Kempffiana11: 76-78.
- ^abcdeGuadagnin DL, Peter AS, Rolon AS, Stenert C, Maltchik L. 2012. Does non-intentional flooding of rice fields after cultivation contribute to waterbird conservation in southern Brazil?Waterbirds35: 371-380.
- ^abcdefghiOlmos F. 1990. Nest predation of plumbeous ibis by capuchin monkeys and greater black hawk. The Wilson Bulletin 102: 169-170.
- ^Sick H. 1985.Ornitologia Brasileira, Umo Introducao.Editora Universidade de Brasilia, Brasilia.
- ^Laubmann A. 1939.Die Vögel von Paraguay,vol. I & II. Strecker and Schröder, Stuttgart.
- ^Schubart O, Aguirre AC, Sick H. 1965. Contribuiçao para o conhecimento da alimntaçao das aves brasileiras. Arquivos de Zoologia do Estado de Sao Paulo, vol. 12.
- ^Web A. 2014. Beautyofbirds. Accessed 06/07/16.https://www.beautyofbirds.com/plumbeousibises.html.
- ^Rodriguez Mata JR, Erize F, Rumboll M.2006.A Field Guide to the Birds of South America.HarperCollins Publishers Limited, London.
- ^abSchönwetter M. 1967. Handbuch der Oologie (W. Meise, ed) Band I. Akademie – Verlag, Berlin.
- ^abBrouwer K, Schrifter H, Jones ML. 1994. Longevity and breeding records of ibises and spoonbills Threskiornithidae in captivity.International Zoo Yearbook33: 94-102.
- ^Reinhard R, Blaszkiewitz B. 1988. Bemerkenswerte Ereignisse in den Vogelrevieren des Berliner Zoos im Jahr 1987.Gefiederte Welt112: 233-236.
- ^Byers O, Brouwer K, Coulter M, Seal US. 1995. Stork, Ibis and Spoonbill Conservation Assignment Management Plan: Working Document. IUCN/SSC Conservation Breeding Specialist Group: Apple Valley, MN.