When explained by Science:

The kiwi is a small, wingless bird related to the ostrich. Because the kiwi has no wings, it obviously can't fly. Kiwis do not have the need to fly; that is why they do not have wings. They have very long beaks, which they use to eat, breathe, and sniff for food. Their beaks are the longest of any bird, and happen to be famous for having nostrils near the tip, rather than closer to the head. They also have powerful legs, like their ostrich cousins. Kiwis also have beady eyes and poor vision, making flying hopeless. Even if they had wings and fair vision, they lack a tail and their bodies tend to be rather short and plump.

When explained by Myth:

Once upon a time, long, long ago, there lived several gods and goddesses in Athens, Greece. They were holding a party for creation, where each god and each goddess would create a creature. Athena, the goddess of war, happened to be sculpting a rather brutal-looking creature. Hades, the king of the Underworld, was looking over Athena's shoulder at the helpless creature.

"Hey, Athena," he taunted, grinning, "your sculpture looks really ugly." He grinned even wider. "If you'll let me make a suggestion...you might want to do this..." Hades stretched out the clay in a spot so it looked like an abnormally long, thin bird's beak.

Athena, having an unusually intolerable temper, got extremely angry. "Look what you've done to my bird! You...you..." She tried to come up with a mean name to call him, but nothing came to mind. The Gods hadn't invented any yet. "You kiwi!" Athena exclaimed.

Hades giggled. "Kiwi? Is that the best you can do? That seems like a name for a bird!" He strolled off, chuckling and muttering under his breath.

That shows what he knows! thought Athena. I might as well make the name useful. So Athena ended up naming the bird a kiwi. But now it was time for Athena to add some unique features. She was brainstorming what to add when Poseidon sauntered over to criticize Athena's creature.

"Ha ha!" the god of the earthquake laughed at her 'masterpiece.' "Athena, you know what could make that thing a little better?" He pointed to the kiwi. "Some pizzazz!" Athena was, this time, fed up with the gods' snide comments. She stood up, grabbed the cushion she was sitting on, and bopped Poseidon over the head with it. He chuckled lously, then snatched Demeter's cushion from under her, and bopped Athena with such strenght, she was knocked off her feet. Zeus, the god of all gods, saw his daughter being knocked off her feet, and came over to smack Demeter over the head with a pillow. He had thought she had committed the awful crime of harming his daughter. When Zeus' cushion actually landed on Poseidon's head (fortunately, his aim wasn't so great), the pillow broke open, and the brown feathers flew all over. When Zeus realized he hadn't harmed Demeter, but Poseidon instead, he apologized and backed up. Zeus then drew a thunderbolt from his belt and aimed for Demeter, having the desire for a little more game. Being Zeus' bolt rather than Eros', the weapon hit Athena's kiwi. Athena screamed out when she saw what her father had done to it. Rather than burning it to a crisp, the kiwi had come to life!

"Father! Father! What have you done?" Athena cried, ashamed for her creature. "Why did you bring my ugly, incomplete, deformed bird to life?" She broke out into a fit of tears, feeling ever so sorry for the bird.

"The world's gotta have some ugly creatures," said Poseidon under his breath.

Ignoring this comment, Zeus said, "It was an accident. I was trying to hit Demeter. Sorry. I'd better go now..." He crept out of the room, blushing.

"What are you going to do with it?" asked Hades. "Whatever you do, don't give it to me!" Everyone laughed.

"I have an idea," exclaimed Demeter, excited. "We can place it on an isolated island. Got any ideas where?" She looked around at Athena, who gave Hera a menacing look.

"New Zealand?" Hera responded automatically. Hera, the queen of the gods and Athena's mother, did not want to experience her daughter's wrath.

Athena nodded. "Yes. Then New Sealand it is. But...other animals live there. What if they laugh at the kiwi?" Athena bit her lip.

"Animals can't laugh," muttered Hades under his breath. Athena glared at him and he frowned immediately.

Poseidon jumped up and down until the earth shook and he started an earthquake. "I know! I know!" Hera asked him to stop jumping. "Alright. We can make the kiwi very curious, so it will be polite an intellectual and smart, and other animals will be curious about it. That way, if they laugh at it, they'll actually have a reason to."

Athena nodded. "Yeah, okay. A grand idea!"

So today, the curious kiwi lives in New Zealand and Australia, has no wings, and has an extra-long beak. Rather than being ugly and pathetic, the kiwi is a very interesting and mysterious bird.