The great kiwi mystery One mystery that still baffles experts is how the kiwi found its way to New Zealand in the first place. There are 68, kiwi left in New Zealand. Kiwi usually live to between 25 and 50 years of age.
They are the only bird with nostrils at the tip of the beak , meaning they have a great sense of smell. Their powerful legs make up a third of their bodyweight, making them fast runners. Their ears are large, giving them a very good sense of hearing. They have been seen tipping their head toward a sound to listen more clearly, much like humans do. So, the kiwi patrols its area every night, leaving smelly droppings to mark boundaries to keep other kiwis away—a very unbird-like behavior. To keep track of each other in the dark, kiwis can shriek loudly, a half scream, half whistle that also serves to scare others away.
The kiwi can also grunt, snort, and hiss when angry. Kiwi pairs use gentle grunts and snuffles with each other and their chicks , and males purr during mating. Pairs do fight, and the larger female may kick the male away if she is not in the mood for his company. An adult male and female kiwi typically pair for life, but a female may choose a new male if a more desirable one wanders by.
The male doesn't have beautiful songs or fancy feathers to attract a female. Instead, he follows one around constantly while grunting. If she's not interested, the female might wander off or try to scare him away. Breeding season is late winter to early summer. Nests might be in hollow logs or in underground burrows dug by the male. The female kiwi lays up to six eggs every year.
Kiwi eggs are smooth and white, off-white, or pale green in color. They are also huge in comparison to the mother: one egg might reach up to 20 percent of her weight; that would be like a pound 54 kilograms human female giving birth to a pound 11 kilograms baby! Compared to the relative weights of other birds and their eggs, the female kiwi should weigh about 31 pounds 14 kilograms rather than its typical weight of 2 to 8 pounds 0.
Kiwi eggs contain almost twice as much yolk as most birds their size and have natural antibacterial and antifungal properties. How did the kiwi evolve to create such a huge egg? The large egg results in a long incubation period.
As ancestral kiwis decreased in size, the egg stayed the same size, allowing for a more developed precocial chick needing less parental care. After the egg is laid, the male takes over parenting duties. He incubates the egg and maintains the nest for nearly 75 to 85 days, but if the female returns to lay another egg, the male has to sit on the clutch that much longer.
Unlike most bird parents, kiwis do not turn their eggs. Lacking an egg tooth, the chick must kick its way out of the shell. The results were staggering, Baker says. The tinamous evolved within ratites, not as a separate lineage. Moa breastbones, toe bones, leg bones, and even the occasional skull rested in the mud, the final resting place for birds chased and slaughtered by humans about 12, years ago. Today, a cast of a Dinornis robustus skeleton towers over visitors to the Royal Ontario Museum where Baker is the senior curator of ornithology.
The tinamous' place on the evolutionary tree offers a glimpse into the origins of flightlessness. All ratites, including tinamous, probably trace their ancestry back to a flying relative, according to Baker. Tinamous retained their ability to fly, while the other lineages each lost flight independently. The study upends an alternate, oft-cited story.
Scientists speculated that the breakup of the supercontinent Pangaea's southern section split up a population of flightless ratite ancestors. Each landlocked group evolved in place, creating the awe-inspiring and quirky birds known today: ostriches in Africa, rheas in South America, emus and cassowaries in Australia, the extinct elephant bird in Madagascar, and kiwis and extinct moas in New Zealand.
The story conveniently explained how flightless birds dispersed across the oceans. But now it looks like each group invaded New Zealand separately. The new evidence doesn't align with the timing of Pangaea's split more than million years ago.
The ratites evolved into separate lineages between 90 and 70 million years ago, and the tinamous and moas diverged about 45 million years ago, according to the study. The debate about these birds has been contentious, Baker says. All rights reserved. The Origins of Flightlessness The tinamous' place on the evolutionary tree offers a glimpse into the origins of flightlessness.
The lack of wings wasn't simply a case of gene loss, he said, and the new study may have offered the answer. That's a tough call. It's the latest instance in which DNA analysis has dramatically changed what we know about many of our native species.
0コメント