#casuariiformes

Southern Cassowary (Casuarius casuarius), father with chick, family Casuariidae, order Casuariiformes, northern QLD, Australia

Southern Cassowary (Casuarius casuarius)

(Sources - 1, 2, 3, 4)

Our next and final order of paleognath birds are the Casuariiformes, composed of one family (Casuariidae), with two genera: Casuarius (“cassowaries”) and Dromaius (“Emu”).

Like most other paleognaths, casuariiformes are large, flightless birds with long legs and necks. They are more colorful than most other paleognaths, with blue necks and cassowaries especially having bright ornamentation and casques on their heads. Cassowaries use their casques to amplify their boom calls, using the low-frequency sounds to communicate in dense rainforests. The casque also acts as a thermal radiator, offloading heat at high temperatures and restricting heat loss at low temperatures. Emus are more adapted for running than cassowaries. Like most other paleognaths, they have reduced wings and retain their wing claws. They have three-toed feet with sharp claws. The inner toe of cassowaries has a dagger-like claw that may be 125 mm (5 in) long, which is used for defense when the bird kicks at predators with its powerful legs. Cassowaries mainly eat fruit, but will also eat small animals, carrion, and seeds, especially in more urbanized areas. Emus eat a variety of plants, such as Acacia, Casuarina, and various grasses. They also eat insects and other arthropods. Cassowaries are typically shy birds that live deep in the rainforest, while emus live in a variety of habitats but are most common in areas of savannah woodland and sclerophyll forest. Casuariiformes are good swimmers, crossing wide rivers and swimming in the sea. They are native to Australia, New Guinea, and some small surrounding islands.

Emus are typically gregarious, traveling in pairs or even in larger flocks when the need arises. Female emus court the males in the Summer months. The skin of the female’s face will turn turquoise-blue and she emits low, monosyllabic calls that have been compared to drum beats. When a male responds, she will parade around him. If two females have their eyes on the same male, they will fight. The male and female form a breeding pair and may remain together for up to five months, establishing and defending their own territory. Males construct a rough nest in a semi-sheltered hollow on the ground, using bark, grass, sticks, and leaves to line it. The pair mate every day or two, and every second or third day the female lays one of a clutch of five to fifteen large, thick-shelled, green eggs. The male becomes broody after his mate starts laying. From this time on, he does not eat, drink, or defecate, and stands only to turn the eggs, which he does about ten times a day. Over the course of the eight-week incubation period, he will lose a third of his weight and will survive on stored body fat and on any morning dew that he can reach from the nest. Some females stay and defend the nest until the chicks start hatching, but most will wander off, and may mate with other males. Newly hatched chicks are active and can leave the nest within a few days of hatching. The male guards the growing chicks, even from other emus such as their mother, for up to seven months, teaching them how to find food. Chicks grow very quickly and are fully grown in five to six months. They may remain with their family group for another six months or so before they split up to breed in their second season.

Meanwhile, cassowaries are solitary, territorial birds except during courtship, egg-laying, and sometimes around ample food supplies. Males and females each maintain separate territories that overlap. While females move among satellite territories of different males, they appear to remain within the same territories for most of their lives, mating with the same, or closely related, males each mating season. Females will broadcast to males when she is ready to mate. Females also sometimes engage in ritualistic chasing behavior, testing the male’s speed and stamina. The male will prepare a heap of leaf litter as a nest, into which females lay three to eight large, bright green or pale green-blue eggs. The male incubates those eggs for 50–52 days, and protects the chicks, which stay in the nest for about 9 months. He defends them fiercely against all potential predators, including humans. The young males later go off to find a territory of their own.

Casuariiformes evolved in at least the Miocene, possibly earlier. It has been suggested that the South American genus Diogenornis was a casuariiform, and not a member of either of the South American paleognaths: the rheas or the tinamous . If this were the case, not only would it extend the fossil range of this lineage to a wider region, but to a broader time span as well, since Diogenornis occurs in the Late Paleocene and is among the earliest known ratites. While the Emu (Dromaius novaehollandiae) has roots in the Middle Miocene, around 11 million years ago, cassowaries (genus Casuarius) are much younger, only arriving around 5 million years ago.

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