Ostrich




Struthio camelus massaicus  


The largest bird in the world, the ostrich reaches a height between 8 and 9 feet tall and weigh about 300 lbs. Males are slightly larger than females. Sexually dimorphic – males have black plumage with white primary feathers on wing tips and tail while females are an earthy brown. The neck and thigh regions in males are bared skinned and pink. In females, these bare areas are pinkish gray.  Newly hatched chicks are fawn with brown spots with a concealing hedgehog-like cape of bristly down on the back.


Family

Struthionidae

Order

Struthioniformes

Class

Aves

Range

East Africa

Habitat

Semi-deserts and savannas

Life Expectancy

Up to 40 years

Sexual Maturity

Females 2 years. Males achieve adult plumage at 2 years but don’t breed until age 3 or 4.

Diet

In the wild, grasses, seeds, leaves, flowers and some animals including invertebrates and small vertebrates (lizards, snakes, young birds and small mammals).

Status

IUCN - Least Concern

Behaviors

Ostriches spend their time gathering food. With heads lowered to the ground, they are very vulnerable to predators. Periodically, they raise their heads to scan the landscape to look for danger. Ostriches nest during the dry season. Males defend territories by patrolling and displaying to and chasing out intruding males. They also “boom,” a surprisingly loud and deep call accompanied by the inflation of the brightly colored neck. Aggressive displays consist of repeated wing flickings and postures with both wings raised. Breeding males display dramatically and a bit absurdly to females squatting and waving their spread wings. Females solicit males by lowering their heads and wings, quivering the latter. Groups of birds are usually small and not cohesive. Adults spend much of their time alone. A male makes a number of shallow scrapes in his territory. A dominant female (“major” hen) with whom he has a loose pair bond, selects one of these scrapes. She lays, on alternate days, up to a dozen eggs. Six or more “minor” hens also lay eggs in the nest, but play no other role. The “major” hen and the male share equally the guarding and incubating duties at the nest site. Females sit on the nest by day and males by night. Unguarded nests are conspicuous from above and vulnerable to predation from Egyptian vultures. These vultures throw stones at the eggs to break them open (shells are nearly 1/10 of an inch thick). Even guarded nests are at risk from hyenas and jackals. Once hatched, young are precocial. Both parents accompany chicks and protect them from raptors and ground predators. Chicks from several different nests usually combine into single large groups escorted by one or two adults. About 15% of those hatched survive to one year of age at which time they reach full height.

Adaptions

Vision is acute. Ostriches have long, powerful legs with two toes on each foot. They are tireless walkers and can run at speeds of up to 31 mph. They can kick to the back and out in front. The claws on the end of each toe can be used to mortally injury predators such as lions. Ostriches are highly efficient, selective gatherers of sparsely dispersed high quality foods – shoots, leaves, flowers and seeds. The takings of many pecks are amassed in the gullet then pass slowly down the neck as a large ball, called a bolus, which stretches the neck skin as it descends. The ostrich egg is not only the largest, but also the smallest in relation to the size of the bird. As a result, an ostrich can cover a great many eggs. Skewed sex ratio among breeding adults (1.4 females: 1 male) and the high rate of nest destruction means that there are many more hens without their own nests. It obviously benefits them to lay their eggs in another’s nest. This is called communal nesting. The “major” hen benefits by the presence of these other eggs because her eggs have a better chance of survival. Her eggs may number 12 among 20 or more. If more eggs are laid than she can cover, the “major” hen rolls away the surplus eggs into an outer ring outside the nest. She is able to distinguish her eggs from the other eggs, an astonishing feat of recognition since eggs are indiscernible in shape and color.

Special Interests

Several groups of flightless birds have been grouped together and called ratites, from the Latin rata, which means, “raft.” These birds lack the well-developed keel bone found in flighted birds and used to anchor flying muscles. No ostrich has yet been observed to bury its head in the sand. Fewer than 10% of nests started survive the three-week laying period and six-week incubation period.

Folklore

Africans have used feathers for adornment. Europeans have used them since Roman times. Being symmetrical, an ostrich feather was the symbol of justice in ancient Egypt where the brains were also a delicacy. Eggshell pieces have been used in necklaces and waistbands. And, in some places, the whole eggshell is said to have magical powers that protect houses and churches from lightning. The Hottentots used empty eggshells as water containers.

Conservation

Increased areas of predator densities and human activity make it unlikely that nests will survive. Excessive hunting drove the Arabian ostrich to extinction early in the 20th Century. Ostrich populations are down due to human encroachment but not severely threatened.

Jacksonville Zoo History

Ostriches have been part of the Zoo’s animal collection since 1961/1962. This species, the Masai ostrich, first appears in the collection records in May 1975. Between 1978 and 1992, the Jacksonville Zoo was the most prolific producer of Masai ostriches of any zoo or park in North America.

Exhibit

Plains of East Africa