Yellow-headed caracara

The yellow-headed caracara (Daptrius chimachima) is new-world bird of prey in the family Falconidae, of the Falconiformes order (true falcons, caracaras and their kin). It is found as far north as Nicaragua, south to Costa Rica and Panamá, every mainland South American country (except Chile), and on the Caribbean islands of Aruba, Bonaire, Curaçao, and Trinidad and Tobago.

Taxonomy and systematics
Louis Pierre Vieillot described the yellow-headed caracara as Polyborus chimachima, putting it in the same genus as the crested caracaras. In 1824, German naturalist Johann Baptist von Spix created the genus Milvago for this species and the closely-related chimango caracara.

The taxonomy of the caracaras has not been settled. The American Ornithological Society and the International Ornithological Committee place the yellow-headed and chimango caracaras in the genus Milvago. BirdLife International's Handbook of the Birds of the World places the yellow-headed caracara alone in Milvago, with the chimango caracara and four others placed in the genus Phalcoboenus. The Clements taxonomy places the yellow-headed, chimango and four other species in the genus Daptrius; the other systems place only the black caracara in Daptrius.

Worldwide systems agree that the yellow-headed caracara has two subspecies, the nominate M. c. chimachima, and M. c. cordata.

A larger, stouter paleosubspecies, M. c. readei, occurred in Florida, and possibly elsewhere, some tens of thousands of years ago, during the Late Pleistocene.

Description
The yellow-headed caracara is 40 to 45 cm long. Males weigh 277 to 335 g and females 307 to 364 g. Their wingspan is 74 to 95 cm. The sexes' plumages are alike. Adults of the nominate subspecies have buff to creamy yellowish white heads, necks, and underparts with a thin dark streak through the eyes. Their back and wings are blackish brown with a whitish patch at the base of the primaries that shows in flight. Their uppertail coverts and tail are buff with dusky bars and the tail has a black band near the end. Their iris is reddish brown surrounded by bare bright yellow skin and their legs and feet are pea green. Immature birds have browner upperparts than adults and their underparts have brown streaks. Subspecies M. c. cordata is a darker buff on the head and underparts than the nominate and has narrower bars on the tail.

Distribution and habitat
Subspecies M. c. cordata is found in southwestern Nicaragua, western Costa Rica, and most of Panama, and in mainland South America from Colombia east through Venezuela and the Guianas, south through Ecuador and Peru east of the Andes, and across Brazil north of the Amazon River. The Nicaragua records are only since 2008, and there are also scattered eBird records as far north as Guatemala and Belize. Off the north coast of the South American mainland, it occurs on Aruba, Trinidad, and Tobago, and has visited Bonaire and Curaçao as a vagrant. The nominate M. c. chimachima is found from eastern Bolivia south through Paraguay into northern Argentina and east through northern Uruguay and Brazil south of the Amazon River. Its range overlaps with that of the chimango caracara in southern Brazil, northern Argentina, Paraguay, and Uruguay.

The yellow-headed caracara is a bird of lightly-treed open landscapes, like savannas with palms and scattered trees, ranchlands and pastures, gallery forests, and the edges of denser forests. In elevation, it mostly ranges from sea level to 1000 m, though it has been recorded at about 2500 m in Colombia's Cauca River valley.

Movement
The yellow-headed caracara is generally sedentary, but records from northern Central America and islands off the north coast of South America indicate that individuals do wander. Within its usual range, it colonizes cleared areas.

Feeding
The yellow-headed caracara is omnivorous and relies heavily on scavenging. Its diet includes carrion, insects (adult and larval), crabs, fish, reptiles, amphibians, mammals, bird eggs and nestlings, horse dung, fruits such as those of oil palm (Elaeis guineensis), coconut, and maize, and seeds. It also takes ticks from cattle and other large mammals like capybaras and tapirs and enlarges open wounds. Much of its diet is taken while walking on the ground, but it does some hunting on the wing. It has also been observed to forage for small invertebrates in the fur of brown-throated three-toed sloths. Mixed-species feeding flocks apparently do not regard it as a threat, not making alarm calls during encounters.

Breeding
The yellow-headed caracara's nesting season varies geographically. It spans from December to April in Costa Rica. In Colombia, there appear to be two seasons, January to April and July to September. It includes August in Venezuela. Egg laying has been recorded in May in Guyana, in July and August in central Brazil, and in September in southern Brazil. It usually builds a stick nest up to 15 m high in a tree or palm but has also nested in a tree cavity, and in the absence of trees on mounds in marshy areas, on the ground, and even in buckets and cans on the wall of a house. The clutch size has been reported as one or two eggs and also as four. The incubation period is about 22 days, fledging occurs 17 to 20 days after hatch, and young are dependent on the parents for about three more weeks. The female does most of the incubating but both parents provide the young.

Vocalization
The yellow-headed caracara is vocal mostly during the breeding season and also when quarreling over food. Its most common calls are a "scratchy wailing keeeah or a more drawn-out keeeeeeeee"; the calls are sometimes made singly but more often repeated. Other calls are a "more growling kraaa-kraaa-kraaa or krrrr-krrrr-krrrr; [a] piercing chay; and [a] thin hissing whistle, ksyeh, ksyeh."

Status
The IUCN has assessed the yellow-headed caracara as being of Least Concern. It has an extremely large range and an estimated population of at least five million mature individuals that is believed to be increasing. No immediate threats have been identified. It "will certainly move into lowland areas as they are converted from forest to cattle ranches or to small- or to medium-scale farming."