Emu Eyes and Nictating Membranes

The Australian Emu (Dromaius novaehollandiae) has protective nictating membranes on its eyes. The membrane over each eye protects them from dust.

A nictating membrane is a transparent or translucent eyelid. The eyelid membrane not only protects the eye from dust, it also moistens the eye and cleans away any dust or dirt. This is because the emu lives in dry, dusty areas of Australia.

Nictating means blinking. The eye membrane is called a third eyelid, or a haw, or a plica semilunaris, or a membrana nictitans.   

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Big bird feathers: Emu, Cassowary, Ostrich, and Rhea

What are the similarities and differences between big bird feathers – the feathers of the largest birds on earth?

The Emu, the Cassowary, the Ostrich, and the Rhea are large flightless ratite birds. The Emu is from Australia, the Cassowary is from northern Australia and New Guinea, the Ostrich is from countries in Africa, and the Rhea is from countries in South America.

Their wings have no keel (anchor) on their sternum (a long flat breastbone) to connect to their wing muscles, which means that the birds can’t fly. Therefore, their feathers are mainly decorative. 

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Rhea Eggs

The Greater Rhea has large eggs, but they are not as large as ostrich eggs.

When a female Rhea lays an egg, it is greenish-yellow at first, and quickly changes to dull creamy-white.

A Rhea egg measures about 13 centimetres (5 inches) long and 9 centimetres (3.5 inches) high, which is half the size of an ostrich egg, and almost twice the size of a chicken egg.

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What is the difference between the Emu and the Rhea?

What is the difference between the Emu (Dromaius novaehollandiae) and the Greater Rhea (Rhea Americana)? 

The Emu and the Greater Rhea are large fightless birds. The Emu and the Greater Rhea are both ratites, because they cannot fly (the Ostrich, Kiwi, and Cassowary are also ratites).

The Emu and the Greater Rhea have a large, soft, grey-brown feathered body, a long featherless neck, and long featherless legs with three toes.

The Emu has orange-brown eyes, whereas the Greater Rhea has blue to brown eyes.

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Greater Rhea

The Greater Rhea (Rhea Americana) is a large bird. It is also known as the American Rhea. It cannot fly. Birds that cannot fly are called ratites. The Ostrich, Kiwi, and Cassowary are also ratites. 

The Greater Rhea is emu-like with a body of large fluffy grey or brown feathers, a long neck, and long legs. It has three toes like the emu (the ostrich has two toes). Its head, neck, rump, and thighs are feathered. 

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Somali Ostrich

The Somali Ostrich (Struthio molybdophanes) is a large bird in the Struthionidae family of ratites. It is also called the Blue-Necked Ostrich. It is a ratite, related to emus, rheas, cassowaries, kiwi, and the Masai Ostrich.

The male Somali Ostrich is a flightless black bird with white tail feathers, a featherless blue-grey neck and featherless grey thighs. The skin of the female’s neck and thighs is grey. The male’s neck and thighs become brighter in mating season. The female and young males have brown feathers. It has the largest eyes of any land vertebrate. The Somali Ostrich has two toes on each foot, whereas most birds have four toes and emus have three toes.

It cannot fly because its feathers lack the tiny hooks that lock together to make external feathers smooth for flying. Its long legs and large wings enable it to zigzag when it runs.

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Masai Ostrich

The Masai Ostrich (Struthio camelus massaicus) is also called the Pink-Necked Ostrich or the East African Ostrich. It is a ratite, related to emus, rheas, cassowaries, and kiwi.

The Masai Ostrich is the largest bird in the world, growing to 2-3 metres (7-9 feet) tall. Their wingspan is about 2 metres (6.5 feet).

It is a large, flightless black bird with white tail feathers, a featherless pink neck and pink thighs. The skin of the female’s neck and thighs is pinkish grey. The male’s neck and thighs are pink, and become brighter in mating season. Females and young males are greyish-brown and white.

They have the largest eyes of any land vertebrate. Their legs have no feathers. The Masai Ostrich has two toes on each foot, whereas most birds have four toes and emus have three toes.

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