Tuesday, 17 November 2015

Those South American 'Geese'

For me at least, one of the highlights of a visit to the far south of South America - loosely known as Patagonia, incorporating the southern extremities of Chile and Argentina - is the presence across the landscape of flocks of big geese. I well recall my first visit to Patagonia, getting a hire car early on Sunday morning and heading out of Punta Arenas to drive along the Strait of Magellan - an amazing experience in itself. I was concentrating on driving on the 'wrong' side of the road for the first time when I suddenly saw a flock of Upland Geese in a wet paddock near the road and risked a rapid U-turn. In the event I needn't have - the next flock was only just down the road, and the next soon after that, and so on. But I was rapt.
Upland Geese Chloephaga picta near Punta Arenas.
This species is dramatically sexually dimorphic; males are black and white with black legs,
while females are rusty brown with orange legs.
This dimorphism doesn't end there either - the males come in two forms, which can be seen in the same flock.
The barred morph has densely black-barred breast and belly. It is commonest around
the Strait of Magellan, including on Tierra del Fuego.
This one was on Isla Magdalena, which is a Chilean island in the famous strait.

The white-breasted form becomes commoner further north - this is in
Torres del Paine National Park.
OK, back to the indicator in the title that these aren't really geese - and they're not, despite the protestations of my good friend Jorge from Chiloé! They are in the same sub-group as the shelducks - whether this is the tribe Tadornini or the slightly more prestigious sub-family Tadorninae is a debate I'll leave for those with more information and more time than I.

There are four members of the genus Chloephaga, all from the cold wind-swept south. All are essentially vegetarian, concentrating - with one interesting exception - on stems and seed heads of grasses and sedges; it is suspected that they are important vectors of these seeds. 

The exception is the surprising Kelp Goose C. hybrida, which lives right in the sea spray, on the often stormy rocky shores and shingle beaches of Patagonia. It does so because it lives almost exclusively on sea weeds (though grazes on grass when breeding on freshwater lakes). 
Kelp Goose pair, Puñuhuil, Isla de Chiloé, Chile.
Another strongly dimorphic species - again the male is much paler.
These are very handsome birds - like all their group - and deserve to be admired from closer up too.
Kelp Geese on Isla Magdalena, Strait of Magellan.
Female above, male below.

The other two members of the genus have identical sexes (except for a minor size difference). Ashy-headed Geese C. poliocephala are relatively common, but nowhere near as readily seen as the abundant Upland Geese. In addition to being less numerous, they are birds of forest clearings in the cold Nothofagus rainforests, so less likely to be seen from vehicles crossing the landscape.
Ashy-headed Geese, Ushaia National Park, Argentinian Tierra del Fuego.
The last Chloephaga species is very scarce indeed on the mainland, where it seems that less than a thousand Ruddy-headed Geese survive; they are still abundant in the Falklands however, despite heavy persecution from farmers. I've only seen them once, on the shores of the Strait of Magellan east of Punta Arenas, and have no really acceptable pictures; this one will have to do I'm afraid!
Ruddy-headed Goose C. poliocephala in the foreground.
(Behind it is a male Kelp Goose and two Crested Ducks Lophonetta specularioides.)
Finally there are two other South American geese (I don't think I need to continue with the apostrophes, which will only make them feel judged - they didn't claim to be anything at all!), both found much further north. They form a separate genus in the shelduck group, though the Andean Goose has only recently (and not unanimously) been moved from Chloephaga .

Andean Geese Neochen melanoptera live in the high Andes - never normally below 3300 metres above sea level (except when exceptional snows force them lower) - from central Chile to central Peru and adjacent Argentina. They are a big bird, weighing up to 3.5 kilograms. A haemoglobin mutation has enabled exceptional oxygen carrying ability, to help them at the high altitudes.
Andean Geese in a bofedale - a high mountain wetland - in the Aguada Blanca National Reserve, southern Peru.
Andean Goslings at the same site.
They lay up to ten eggs in a nest on the ground.
Just one member of this group prefers the heat of the tropical lowlands. The Orinoco Goose is found along streams throughout much of the northern Amazon basin, though it is loath to actually take to the water. It is rarely common; indeed in Peru it is listed as Critically Endangered. Both Neochen geese, like their southern relatives, are vegetarian grazers.
Orinoco Goose, Manu National Park, Amazonian Peru.
They don't have the cachet of Jaguars, Condors, macaws or toucans, but I reckon the South American geese (or 'geese') are a special little part of that wonderful continent.

BACK ON THURSDAY (26 November)


Flabmeister said...

You comment on the Kelp Geeses eating sea weeds. Is this algae or flowering plants which grow in the sea?

Ian Fraser said...

Sorry, no I meant seaweed as generally used - ie various species of algae, harvested on land rather than in the water. Maybe other birds do this, but I can't think of any.

Flabmeister said...

Ta: I'd never heard of birds eating algae and hence my question.

Mind you we did see 68 Pied Cormorants roosting in the drifts of dried algae (2-3m deep)on the beach at Kingston SE last week. Perhaps they took a nibble as a change from fish????

Ian Fraser said...

Sort of cormorant sushi??? Well, I guess anything's possible.... But.

Les Mitchell said...

Thanks Ian. Another interesting and informative article. Lovely group of animals.