Joe St. Jean, age 12, of Coventry, Rhode Island, for his question:

How does an emu differ from an ostrich?

You might mistake the Australian emu for a smallish cousin of the African ostrich but zoologists classify them in different orders. The emu is classed with the helmeted cassowary, which hides himself in Australia's forests. The ostrich is the only bird with only two toes per foot, which is one reason why he is classed alone in an order of his own. He also is the world's largest living bird but the emu ranks in second place.

The stately ostrich may stand eight feet tall and weighs up to 345 pounds. He stands with his skinny, four foot neck erect and looks like what he is the Largest Living Bird. The emu weighs about a hundred pounds and may be six feet tall. However, he tends to slump, which makes him look shorter than he is. The ostrich, though unable, to fly, never misses a chance to spread and display his handsome wings. The emu's little wings are hidden in his shaggy brown feathers.

These big flightless birds may occupy neighboring homes in a zoo. But in the wild their habitats are a world apart. A few centuries ago, several species of ostrich roamed through most of Africa. Now the sole surviving species lives mainly on the plains. A few centuries ago, several species of emu lived in Australia and on the nearby islands. Now the sole surviving species keeps mainly to the central plains of Australia.

Though not closely related, both are ratite, non flying birds. The word "ratite" means "raft" and refers to the blocky shaped breastbone. Most birds have keel shaped breastbones, angled like the keel of a ship, to support their large, powerful flying muscles. However, even if the ostrich and the emu had keel breastbones, they could not fly. The heaviest flying birds are around 40 pounds. The big ratites would be grounded on account of being overweight.

Aside from looking very much alike, the ostrich and the emu share similar life styles. Both roam around in large family groups, seeking every available type of food. When in a hurry, they can race long distances at 40 miles an hour.

Both birds raise their chicks in hollows in the ground but they have different ideas about family life. The male ostrich, adorned with magnificent black and white plumage, may have one or two or three wives. The brown females of the family all lay their eggs in the same hollow nest, which may be nine feet wide. Then one female shoos the others away and takes over the brooding while the male stands guard.

The emus separate from the flock in pairs and the male prepares the nest. Both parents have shaggy brown plumage, though the female is slightly larger than the male. After she lays the eggs, she leaves and he settles down to keep them warm for two months.

One ostrich egg is big enough to make an omelet for a sizeable family. It is six inches long and weighs two and a half pounds. An emu's egg weighs about a pound and a half which is big enough to make a birthday cake for a baseball team.