I think the <pompous>scientific</pompous> literature can confirm the existence of the creature if two of the legs are discarded. The hoatzin (apparently pronounced Watson) is interesting as its taxonomic position is still unresolved: nobody can convince rival taxonomists that its nearest rellies are cuckoos or doves or turacos.
|4983. Wed Jan 21, 2004 11:56 am|
|4984. Wed Jan 21, 2004 12:01 pm|
|5519. Sun Feb 01, 2004 7:59 pm|
|Maybe this should go under the General Ignorance thread as well, because this came as a surprise to me when I saw it today. I always thought the use of canaries in coal mines was a nineteenth century thing, but in fact they weren't phased out until 30th December 1986.
|6221. Wed Feb 25, 2004 6:02 am|
|Kiwis share so many characteristics with mammals that they're described as an "honorary mammal". The theory is that because New Zealand had no native mammals for millions of years, and was so isolated from other land masses, kiwis (and the other large birds native to NZ like the moa) evolved to fill niches which in the rest of the world are filled by mammals. Also, because they had no mammal predators, they were able to behave in a way which would have got them killed anywhere else, eg. living on the ground.
Their mammalian features include:
-they have whiskers, like a cat, on the face and around the base of the neck;
-they have a highly developed sense of smell, which enables them to find food by smell alone. As Garrick pointed out, they have nostrils on their beaks - in fact, they're the only birds with exterior nostrils. Their sense of smell (the size of their olfactory bulb in relation to their forebrain) is second only to the condor;
-they have a well-developed sense of hearing;
- their body temperature is much lower than other birds, closer to a mammal's body temperature;
-they have a shaggy, hair-like plumage. They aren't born covered in down, but in a slimy coat, which dries and flakes off within 24 hours, leaving them with their full plumage;
- their skeletons are different even from other ratites (flightless birds). All ratites have undeveloped flight muscles, which means that they don't need a keeled sternum to support the muscles. But a kiwi's actual bones are not filled with air sacs to make them super-light, like other birds. Their bones contain marrow, like a mammal. That also makes their legs strong and powerful;
-they have 4 toes instead of 2 or 3, like most birds;
- their large feet have fleshy footpads, so they can walk almost silently;
- their eye sockets are not separated by a plate like most birds, but are divided by a large nasal cavity;
- they live on the ground, either in burrows, or in natural hollows like tree roots. They dig their burrows with their powerful legs and claws, and some species build a labyrinthine system of tunnels;
- their skin is very tough, like a hide;
- they ovulate from both ovaries, like a mammal, whereas birds only use one. In most birds, only the right ovary functions, unless it becomes damaged, in which case the underdeveloped left ovary surges into action, as an ovatestis, secreting testosterone, which masculinises the bird. The only theory I could find for why birds use only one ovary is that they need their bodies to be as light as possible, so if only one ovary is necessary, then why bother developing both. Two developing eggs would be inconveniently heavy. This is also the theory for why birds don't have a bladder - a waste of space.
S: Bully for Bronatasaurus, Steven Jay Gould
|6223. Wed Feb 25, 2004 6:45 am|
|Kiwi reproduction: this is raw nature. It made me feel quite sick.
It takes 30 days for the female to form an egg, and during this time, she has to eat three times as much as normal, to feed the developing foetus. However, she has to fast for the last 2 or 3 days before she lays the egg, as the egg is so massive that there is hardly any room left for her stomach.
An egg can be between 15 and 25% of the female's body weight, 6 times bigger than you might expect from another bird the same size. By inter-species ratio, a chicken and a kiwi the same size would produce eggs weighing 55-100 and 400-435 grams respectively. There is an x-ray of a pregnant kiwi on www.kiwirecovery.org.nz.
The preganant mother's belly is so distended by this massive egg, that it actually touches the ground. She has to walk with her legs splayed, and soaks her belly in cold water, both to soothe the stretched skin and to take some of the weight off.
The egg contains 65% yolk, a massive amount compared to most birds, whose eggs contain closer to 25% yolk. Birds whose eggs contain a high yolk percentage are born far more developed than birds from eggs with relatively little yolk. Sparrows, for example, are born from an egg with about 25% yolk, and are blind, naked and helpless. The kiwi is born with its eyes open and full plumage. The nutrition from the yolk sustains the newborn kiwi for several days after it hatches, so it doesn't need to eat. In fact, the hatchling kiwi is so gorged with the yolk that its belly is too distended for the kiwi to stand, as the legs simply can't support the weight. Its about 2 or 3 days before the hatchling has absorbed enough of the yolk sac to be able to stand and shuffle around the burrow.
Incubation differs between species of kiwi: Little Spotted Kiwi and Brown Kiwi breed in pairs and only the male incubates the egg; Great Spotted Kiwi, Rowi and Haast Tokoeka breed as pairs, and both adults share incubation; the male, female and a group of helpers share incubation amongst Southern Tokoeka. Because the male is smaller than the female, the egg is even bigger in proportion to a male's body size, so it's not incredibly easy for a male to position himself so he's completely covering and protecting the egg.
The incubation period is between 70 and 80 days, much longer than of a similar-sized bird, but about the same time as for a similar-sized mammal. This is probably because the body temperature is so low. Hatching can take up to 3 days. The parent then stamps on the shell to break it up, and either buries it in the nest, or eats it, for its calcium.
S: as above and www.gi.alaska.edu
|6226. Wed Feb 25, 2004 7:10 am|
|Baby kiwis are so vulnerable to predators that only about 5% survive to adulthood.|
|6279. Tue Mar 02, 2004 4:34 am|
|6283. Tue Mar 02, 2004 6:33 am|
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