Upland goose
Template:Short description Template:Speciesbox
The upland goose or Magellan goose (Chloephaga picta) is a sheldgoose of the shelduck-sheldgoose subfamily of the Anatidae, the biological family that includes the ducks and most duck-like waterfowl such as the geese and swans.<ref name=":0">Template:Cite journal</ref><ref name=":1" /> Sheldgeese resemble true geese and display similar habits, yet they are more closely related to shelducks and ducks.<ref name=":1" /> The two recognized subspecies of upland goose are the continental picta subspecies and the insular (island) leucoptera subspecies.
This species nests and breeds close to water (rivers, ponds, oceans) either on the ground or near it among vegetation, usually in grasslands or coastal meadows in the Falkland Islands or in southern Patagonia and Tierra del Fuego at the beginning of the austral summer. Population estimates suggest the insular subpopulations are stable, but continental populations show a recent decline in abundance.<ref name=":1">Template:Cite journal</ref> Upland geese are herbivores, specializing in plant leaves, stems and seeds.<ref name=":0" /><ref name=":5" />
Taxonomy
The upland goose 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 other ducks, geese and swans in the genus Anas and coined the binomial name Anas picta.<ref>Template:Cite book</ref> Gmelin based his description on the "Painted goose" that had been included by the English ornithologist John Latham in his A General Synopsis of Birds. The species had been observed in 1775 on the Isla de los Estados (Staten Island) during Captain James Cook's second voyage to the Pacific Ocean.<ref>Template:Cite book</ref> The naturalist Joseph Banks had provided Latham with a water-colour drawing of the goose by Georg Forster who had accompanied James Cook. It is the holotype for the species and is held by the Natural History Museum in London.<ref>Template:Cite journal</ref> The upland goose is now placed with four other species in the genus Chloephaga that was introduced in 1838 by the English naturalist Thomas Campbell Eyton.<ref>Template:Cite book</ref><ref name=ioc>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The genus name comes from the Ancient Greek khloē meaning "grass" and -phagos meaning "-eating". The specific epithet picta is from Latin pictus meaning "painted.<ref>Template:Cite book</ref>
There are strong morphological and genetic similarities between the bird fauna of the Falkland Islands and southern South America,<ref name=":1" /> and most native bird species are usually present in both insular and continental populations. The biogeography of the region suggests that these similarities exist because in the geological past, birds from the continent might have reached the Falkland Islands either across a former land connection, during periods of lowered sea levels, or through long-distance dispersal.<ref>Template:Cite journal</ref> Genetic analyses place the Magellan goose as a sister taxa to the kelp goose.<ref name=":1" />
Subspecies
Two subspecies of upland goose are recognised.<ref name=ioc/> The smaller mainland form, picta, also known as the lesser Magellan goose, is found from central Chile and south-central Argentina south to Tierra del Fuego. The larger insular form, leucoptera or greater Magellan goose, is indigenous to the Falkland Islands, located to the east of the southern part of South America.<ref name=":0" /><ref name=":1" />
Description
Upland geese males are similar to other sheldgeese, notably the kelp goose (Chloephaga hybrida) due to their predominantly white plumage, while females resemble the ruddy-headed goose (C. rubidiceps) due to their similarly barred breast plumage. This species is 60–72.5 centimetres (23.6–28.5 in) long.<ref name=":0" />
Greater Magellan geese (leucoptera subspecies) are the largest birds of the Chloephaga genus. Males typically weigh 3.5–4.5 kg (7.7–9.9 lbs) and females range from 2.9 to 3.5 kg (6.4–7.7 lbs).<ref name=":0" /> Lesser Magellan geese (picta subspecies) males weigh 2.7–3.6 kg (6.0–7.9 lbs) on average and females 2.9–3.5 kg (6.4–6.8 lbs).<ref name=":0" />
Upland geese display strong sexual dimorphism in their plumage. Males have white heads and breast plumage with black legs, whereas females have reddish-brown heads and breast plumage with yellow-orange legs.<ref>Template:Cite journal</ref> However, two interbreeding morphs exist for males. One morph causes black-barred breast plumage while the other causes white breast plumage. A greenish-bronze speculum is also located on the inner secondary flight feathers of the adult male.<ref name="zipcodezoo">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Males make a whistling "wheep" sound, while females make a low, rattling "a-rrr" sound.<ref name=":0" />
Upland geese molt both their primary and secondary feathers in ponds or sheltered sea inlets, usually between late November and early January. Molting frequency depends on breeding success to some degree, since most adults that molt have either not yet mated or failed to breed.<ref name=":2">Template:Cite journal</ref> Some greater Magellan geese skip this molt, retaining their ability to fly during the austral summer. While unusual, skipping this important process might have energetic advantages, since molting season can be very nutritionally taxing.<ref>Template:Cite journal</ref>
In Chapter VI of On the Origin of Species, author Charles Darwin noted that the upland goose has webbing between its toes that appeared to be "rudimentary in function, though not in structure", and concluded that this was a vestigial anatomical feature in this bird.<ref name=Darwin1859>Template:Cite book</ref>
Habitat and distribution
Habitat
Upland geese usually live in small, scattered groups on most pasture types (temperate grasslands, arid lowland scrubs), favouring areas with short green grasses. However, recent land use changes towards crop fields and managed pastures have forced them to adapt to and colonize such modern landscapes.<ref name=":0" /><ref name=":4">Template:Cite journal</ref>
Distribution
Upland geese occupy the southern South American Continent (southern and central Chile and Argentina) and the Falkland Islands, with a continental distribution ranging from central Chile/southern Argentina to Tierra del Fuego, near Antarctica. Lesser Magellan geese usually reside in Patagonia or southern Chile and migrate north during the winter towards central Argentina, to their wintering grounds.<ref name=":0" /><ref name=":1" /> Southernmost populations are more likely to migrate,<ref name=":3">Template:Cite journal</ref> with migrants reaching flight speeds of over Template:Cvt.<ref name=":4"/> In 2013, researchers identified a lesser Magellan goose in southern Brazil, redefining the northern edge of their wintering grounds.<ref name=":3" /> Greater Magellan geese, however, do not migrate and rarely leave the Falkland Islands.<ref name=":0" /><ref name=":1" /> In general, population densities are highest around ponds and in green grasslands. Computer modelling of population ranges suggests that their distribution is favoured by the ample presence of green grasses to feed and breed in, and hindered by human presence, notably urbanization and oil extraction.<ref>Template:Cite journal</ref> There is also a sizeable introduced population on the sub-Antarctic South Georgia Island.<ref name=":0" /><ref>A Field Guide to the Wildlife of South Georgia; Princeton University Press 2012</ref>
Behaviour and ecology
Breeding
Upland goose breed in southern Patagonia or their native islands during the austral summer. They are monogamous, although divorce can occur, and generally return to breed in the same territory every year.<ref name=":0" /><ref name=":2" /> After approximately two years from birth, females can start to lay eggs, and usually do so near their birthplace. Males begin breeding later and tend to settle farther away from where they were born.<ref name=":2" /> This sexual difference in dispersal distances causes the sex ratio of young to become biased towards the dispersing sex due to the inherent resource constraints of crowding. Therefore, upland geese tend to display a male-biased sex ratio.<ref>Template:Cite journal</ref> They breed non-colonially in densely vegetated areas, generally in September and October on the mainland, and in November on the Falkland Islands.<ref name=":2" /> A large population of this species breeds in the New Island Nature Reserve,<ref name=":7">Template:Cite journal</ref> which was created in collaboration with Falkland Conservation.
Males attract females through a courtship display in which they whistle loudly, to which the female responds with softer cackles. As they are monogamous and territorial, a violent fight may break out if a male encroaches on another's territory. Males have been found injured or dead after these fights.<ref name="Upland Goose">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
The simple nest is either on the ground or within Template:Cvt of it, usually concealed by dense vegetation, and often located near water.<ref name=":0" /> A clutch consists of 5–8 eggs which are incubated for about 1 month.<ref name=":0" /><ref name=":2" /> When the chicks hatch, they are covered in greyish-brown down. They don't remain in the nest for more than a day, quickly going to a nearby water source or feeding area, and are able to feed themselves from birth. They fledge in 9–10 weeks and reach maturity in 3 years.<ref name=":0" /><ref name=":2" /><ref name="Upland Goose"/>
Food and feeding
The upland goose is primarily a herbivore, feeding mostly of seeds, leaves, stems, and other plant matter. They are very gregarious, and flocks of thousands of birds can be found grazing in one pasture alone. They are considered pests by farmers due to the fact that they eat on the pastures that are used for cattle and sheep, and because they claim that upland geese significantly decrease crop yield.<ref name=":5">Template:Cite journal</ref> However, a recent study claims that while sheldgeese do reduce wheat cover, they do not reduce overall wheat yield and they might even provide an ecosystem service through weed grazing.<ref>Template:Cite journal</ref>
Threats and conservation
In the early 20th century, the Argentinian government declared the three Patagonian sheldgeese species (Ruddy-headed goose, Ashy-headed goose, and Upland goose) as pests due to claims of excessive grazing and negative effects on crop yields.<ref name=":4" /> Since then, wildlife agencies have encouraged hunting of upland geese across the entirety of their range and without restrictions on the number of birds killed. Consequently, population surveys started suggesting continental populations were declining.<ref name=":1" /> In 2008, all three species were classified as endangered by the Argentine government and hunting was banned, although some poaching still occurs, mostly on the mainland.<ref name=":4"/> Recently, fox predation has drastically reduced population numbers on the mainland,<ref name=":7" /> so national governments have established several protected areas throughout Patagonia in an attempt to conserve the species.<ref>Template:Cite journal</ref>
References
External links
- Male vocalizations on Birds of the World
- Female vocalizations on Birds of the World
- New Island Nature Reserve