The black-legged seriema (Chunga burmeisteri ) is one of two living species of seriemas in the family Cariamidae. It is found from southeastern Bolivia and northern Paraguay south into north-central Argentina. It is a large, mostly grey bird with a long neck, a long tail, and long, slender black legs. Its belly, vent and thighs are yellowish-white. The sexes look similar, as do immature birds, though the latter are more patterned on head, neck and back. First described for science by Gustav Hartlaub in 1860, it is monotypic, with no subspecies. Like its red-legged cousin, it is an omnivore. It seldom flies, instead pursuing prey and eluding danger on foot. Its loud calls, said to sound like kookaburras, turkeys or yelping dogs, are often given in duet. Little is known about its breeding ecology. It is known to breed in November and December, building a platform nest of sticks and laying two white eggs, which are sometimes marked with a few brownish or purple spots. The International Union for Conservation of Nature rates the species as one of least concern, due to its large range and apparently stable numbers.
The black-legged seriema is a large bird, measuring some 70–85 cm (28–33 in) in length, and weighing roughly 1.2 kg (2.6 lb). This makes it one of the largest ground-dwelling birds in the Neotropics; only the red-legged seriema and the rheas are larger. It is long-necked and long-tailed, with very long, slender legs and short, rounded wings. Overall, it is ash-grey in colour, though closer examination shows that the "grey" body feathers are actually finely vermiculated with black and white. It has an inconspicuous frontal crest, composed of erect, hairlike bristles. It has whitish supercilia and lores, and the feathers on its crown and nape are barred in black and white. Its belly is paler grey, and its lower abdomen, crissum and thighs are yellowish-white. The flight feathers on the wings are thickly barred with black and white, and its grey tail is barred and narrowly tipped with black. Its feathers are loosely webbed, giving the bird a "soft" appearance. Those on its nape are particularly long, forming an inconspicuous crest. Its stout black bill has a strongly decurved culmen and a small hook at the tip. Its iris is reddish-brown, and its legs are dark-grey to black. Its feet have three short front toes with very sharp claws, and one small elevated hind toe. The sexes look alike, and youngsters are similar, though somewhat more patterned. The latters' heads, necks and breasts are barred, and their backs and upperwing coverts are speckled with white.
Found from southeastern Bolivia and northern Paraguay south into north-central Argentina, the black-legged seriema is a dry-country bird of savanna, shrubland and dry, open forest, including the Dry Chaco and the Monte Desert. Perhaps surprisingly, the species was not known from Bolivia until the late 1970s. It is generally found at elevations below 800 m (2,600 ft), lower than the elevations at which the red-legged seriema is typically found. Though it will forage in untreed areas, including cultivated fields and grassy plains, it only does so when there are wooded areas nearby.
The black-legged seriema spends much of its time on the ground, and flies only reluctantly. It is a fast runner, and typically chases prey and eludes predators on foot. If pressed, it is capable of short flight – rapid flapping, followed by a glide. It sometimes flies up into trees, though it will preferentially jump to lower branches. Although it is primarily a sedentary species, some local movements may occur. In Paraguay, for example, it is known to move out of some areas of the chaco in response to cooler weather.
Black-legged seriemas are omnivorous. Insects, particularly beetles and locusts, make up a significant portion of their diet, and they take the occasional rodent. They also eat plant material, including leaves, grass and seeds. They often hunt around the feet of livestock, which presumably flush insects as they move.
The breeding behaviour of the black-legged seriema is not well-known. It is thought to breed primarily from November into December. It nests solitarily, with both members of the pair building a platform of sticks in a tree. The female lays two white eggs, which measure 56–61 mm (2.2–2.4 in) x 42–46 mm (1.7–1.8 in) and may have a few brown or pale purple spots.
Because of the black-legged seriema's very large range and apparently stable population, the International Union for Conservation of Nature considers it be a species of least concern. Although its numbers have not been quantified, it is said to be "fairly common" throughout its range in Argentina. Its status in Bolivia and Paraguay is not well-documented. It is potentially impacted by habitat loss and fragmentation. One study in Argentina found the bird disappeared from parts of its former range once the forest had been fragmented into plots of less than 280 ha (690 acres).
It is known to harbour the chewing louse species Tinamotaecola wardi, Tinamotaecola andinae, Colpocephalum cristatae and Colpocephalum caudatum.
