With generally higher body temperatures than mammals, birds are better
equipped for survival in the searing desert heat. Most birds, too, are able to fly
long distances in order to find water, or to move on if a dry spell becomes too
acute. Consequently many bird species are found on the fringes of, though rarely
deep inside, true deserts; they include the world’s two largest birds, as well as
some of the smallest.
The ostrich (Struthio camelus) stands over 2.5 meters (8 ft.) tall and is not
only the biggest living bird but also the fastest creature on two legs, striding
with enormous paces, rather than running, at more than 70 kilometers per hour
(43 mph). It is ideally suited to grasslands and arid patches across Africa,
including the fringes of the Sahara. Its wings are useless for flight but their soft
plumes provide shade for the lower body, especially the almost naked patches of
skin just beneath the wings where excess body heat radiates into the air.
Ostriches are desert nomads, wandering wherever the rains encourage plant
growth so that they can feed on shoots, buds, leaves, seeds, and other vegetation.
However, in the tradition of true desert survivors, they are not fussy and also
peck up insects, little lizards, mice, and other small animals.
When conditions are suitable, the male ostrich rounds up a harem of several
females. The chief female scrapes a shallow nest and lays her eggs, and the others may add to their
number. The eggs are gigantic, each one up to 15 centimeters (6 in.) long and
the equivalent of 30 to 40 hen’s eggs in volume. The chief female sits on them
by day, more often to shade them from excessive heat rather than to keep them
warm, while the male takes over incubation at night. The eggs hatch after 40 or
so days, and the young birds can run and adopt a nomadic lifestyle almost
immediately.
Second in size only to the ostrich, the emu (Dromaius novaehollandiae) of
Australia also speeds across the desert with huge 3-meter (1-ft.) strides, and is
able to sprint at 60 kilometers per hour (37 mph) for short bursts. Its diet is even
wider than the ostrich’s, comprising seeds, fruits, leaves, insects, worms, farm
crops, and carrion. The female lays eight to ten greenish-brown eggs in a nest 1
meter (40 in.) across, under a tree or bush, while the male is both the nest’s
constructor and the major incubator, sitting on the eggs for two months. When
extreme drought forces emus from the outback, they can invade farmland and
become serious pests. The third-largest birds are the rheas (Rhea americana and
others) of South America. They, too, are wanderers of grassland, arid scrub, and
open country and have a similar diet to the ostrich.
At the other end of the size spectrum from the emu, arid Australia is also
home to the budgerigar (Melopsittacus undulatus), one of the smallest members
of the parrot family. “Budgies” of all colors are familiar as cage birds around the
world, but those of the outback are predominantly green. Noisy and gregarious,
they drink early in the morning at a local pool or wait until a kangaroo or similar
large animal has scraped a hole in the soil to get at water. Having quenched their
thirst, they take off as a whirling, wheeling, chattering flock for a morning feed
of grass seeds. After roosting in the shade during the heat of midday, they feed
again toward evening and then settle for their night’s rest.
As with emus and ostriches, budgerigars are nomadic. However, during their
rainfall-triggered breeding season, they stay put as a colony for a few weeks,
nesting in holes in tree trunks, old logs, and rock crevices. The female incubates
her four to seven eggs for about 18 days, and the offspring are ready to fly after
four weeks.
Another desert mini-resident is the elf owl (Micrathene whitneyi) of
southwest North America, which measures only about 13 centimeters (5 in.)
long from its beak to the tip of its very short tail—about the size of a human
hand. It roosts by day in a tree, bush, or tall cactus, such as the saguaro. At night
it is a predator of flying insects such as moths, beetles, grasshoppers, and
crickets. Unusually for an owl, it can hover to snatch victims from foliage, and it
also swoops to the ground for small lizards, snakes, and scorpions—hastily
nipping off the poisonous sting. The elf owl’s usual nesting site is a hole in a
tree or large cactus, perhaps excavated by a gila woodpecker. The female
incubates her two to five eggs for about 25 days and the male feeds both her and
the chicks when they hatch.
Since lizards and snakes are relatively common in many desert regions,
several birds habitually feed on them. In the Sonoran, Mojave, and nearby areas
of North America the greater roadrunner (Geococcyx californiana), a member of
the cuckoo family, resembles a rooster with a dark head crest and long, straight
tail. It can run at speed, up to 25 kilometers per hour (16 mph), preferring to use
its legs rather than its wings. The roadrunner feeds on a range of small creatures,
including grasshoppers, crickets, and other insects, but also birds’ eggs, lizards,
and snakes—even poisonous varieties such as the rattlesnake. Roadrunners pair
for life and raise their three to six chicks in a bush or clump of cacti.
In African deserts south of the Sahara the secretary bird (Sagittarius
serpentarius) stalks the dry bush, on the lookout for snakes and lizards as well
as small mammals, birds, and insects. This tall, stately bird has very long legs
and can stride more than 30 kilometers (19 mi.) on a day’s foraging. Like the
roadrunner, it kills prey with a very swift, hard peck, usually to the neck region,
or it may pin down its victim with its large, strong, heavily scaled feet or even
stamp it to death. In some regions the secretary bird is protected by laws or local
traditions because of the toll it takes of poisonous snakes. The species is named
from the head crest of several long feathers that protrude upward and back, like
the quill pens that a human scribe of previous centuries might have put behind
his or her ear.
Several larger birds of prey range huge distances over arid grassland, scrub,
and desert in search of victims. The lanner falcon (Falco biarmicus) soars across
dry areas of Africa south of the Sahara, including the Kalahari Desert, and over
the Middle East, and is rarely found in areas with annual rainfall of more than 60
centimeters (23 in.). This falcon is a majestic hunter, with a wingspan of almost
1 meter (3 ft.), its black forehead and “moustache” contrasting with the white
cheeks and throat and blue-brown back with creamy-buff underparts. Unusually
for falcons, it often attacks prey on the ground or just above, taking small and
medium-sized birds, rodents, bats, and lizards.
In southern North America and South America the smaller, colorful, and
adaptable aplomado falcon (Falco femoralis) is a species found in dry, open
lands characterized by grasses, cacti, and mesquites. Like many arid-land birds,
it sweeps to and fro near bushfires for insects and small birds that have been
disturbed by the flames.
In Australia one of the world’s largest birds of prey, the wedge-tailed eagle
(Aquila audax), is a familiar sight over the dry outback. It is glossy brown-black
and measures 1 meter (3 ft.) from beak to wedge-shaped tail—its distinguishing
feature as it soars in search of rabbits, hares, small wallabies, and young
kangaroos. Like many other birds of prey,
it also takes carrion and is sometimes persecuted by humans for killing lambs
when it is in reality only scavenging on a dying or already dead carcass. Another
well-known avian scavenger throughout the Americas is the turkey vulture
(Cathartes aura), with its mainly black plumage, bare head and neck, purplish
face, and white beak. It ranges from deserts to forests and gathers in
considerable numbers at a large carcass, or feeds on birds’ eggs, chicks, and
even old fruit.