Posted by: Rob Viens | August 13, 2012

A Wish for Wing that Work

On August 13th things quieted down enough in town to allow some shore leave.  Darwin writes:

“At last the unsettled politicks & weather have permitted us to walk in the country: Wickham, Sullivan, Hammond & myself went out shooting & if our sport was not very good the exercise was most delightful.” (Aug 13)

Darwin was thrilled to be able to go exploring. However, I can’t help but notice that the two senior officers and the new midshipman accompanied him.  I wonder – were they there to make sure nothing got out of hand, or was it just that their senior positions (and experience with Montevideo in Hammond’s case) allowed them to leave the ship.

The group had a goal in mind:

“Hammond & myself walked in a direct line for several miles to some plains covered with thistles, where we hoped to find a flock of Ostriches.— We saw one in the distance; if I had been by myself, I should have said it was a very large deer running like a race-horse.— as the distance increased it looked more like a large hawk skimming over the ground.— the rapidity of its movements were astonishing.” (Aug 13)

Nice image of a hawk/deer/horse beast :).

The “ostriches” that Darwin refers to here were actually rheas.  I’ll say a little more about them later when Darwin observes them in much more detail, but I thought I might touch on a few general comments about “ratites” today.

The ratites are a group of generally large, flightless birds.  This group of birds has lost the ability to fly (fossil evidence points to the fact that their ancestors did fly).  In fact, their sternum has no “keel” – the ridge of bone that supports the muscles of the wing.  So no matter how much they work out or wish for wings, without some serious evolution of bone structure they won’t be flying again.

Comparison of ratites (from Te Ara – The Encyclopedia of New Zealand):

Ratites

 

Along with the rhea and ostrich, the living ratites include the emu, cassowary, and the kiwi.  Recently extinct species include the moa and elephant bird.  Their demise corresponded with the arrival of humans on New Zealand and Madagascar respectively.  Alas, as an old New Zealand folk song goes – “there ain’t no moa”.

Together, the ratites span the southern hemisphere, having representatives in South America (rhea), Africa (ostrich), Madagascar (elephant bird), New Guinea & Australia (cassowary), Australia (emu) and New Zealand (moa).

 

Cassowary (from casuarius.webs.com)

Cassowary

Emu (ah, one of my own shots from the Cougar Mountain Zoo)

Emu

Some of the extinct species where quite large.  The greater moa grew to over 3.5 meters (about 12 feet) and the larger elephant bird weighed in at close to 400 kg (about 900 pounds)! Both their large size and the fact that they went extinct quite quickly when humans showed up are probably the result of living on large islands.  In the first case there is even a name for this phenomenon – island gigantism – the tendency of some species evolving on islands to grow larger than their mainland cousins.  (The Galapagos Tortoises fit this mold, too,) The second issue is a result of introducing a major new predator (humans) into a relatively small island ecosystem. History shows that such situations never end well.

Elephant Bird (from Vanished Species by David Day, Gallery Books 1989 revision)

Elephant Bird

Darwin will have a lot to say about the Rhea over the coming months, so I’ll come back to our ratite friends again,

The long day ended with everyone tired out.  Luckily, a ride arrived:

“As the breeze was rather too stiff for boats, it had been determined to walk from the Mount round the bay to the town.— When far distant from it, Wickham & Sullivan found themselves so tired, that they declared they could move no further.— By good luck a horseman came up, whom we hired to carry them by turns till another horse was found; & thus we arrived just before the city gates were closed for the night.” (Aug 13)

It must have good to spend a day in the country for the first time since the end of June. After several nights of gunfire, I bet Darwin slept well tonight. (RJV)

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Responses

  1. […] (For more on rheas and other ratites see A Wish for Wings that Work.) […]

  2. […] more on rheas (Darwin’s ostriches) and guanacos (New World camels) see A Wish for Wing that Work and The Guanaco Family […]

  3. […] the Greater Rhea is one of two living species of Rhea (for more on Rheas and other ratites see A Wish for Wing that Work). Finding new species, especially large mammals or birds, was especially exciting for Darwin, who […]


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