This species is about 24 cm long. The bill is oddly shaped: long, slender, and very sharp, looking almost upturned. Adults of both sexes are described by their name. Juveniles have entirely black plumage; orange-red feathers first appear on their breast and throat, later spreading to the neck, head, and thighs. The song is given as "loud, clear, and melodic, a ringing 'cleer-cleer-clur, clulululu'." Calls are simpler but have a similar quality.
Scarlet-headed Blackbirds occur in pairs in large reed beds in southern Brazil, Paraguay, Uruguay, and northeastern Argentina; Bolivia has an isolated population at altitudes up to about 600 m. They often perch conspicuously on top of stems. They are uncommon, particularly away from the coast.
They eat mainly fruit, supplementing it with seeds and invertebrates, especially insects. They use their bill as a hammer to open food items.
- BirdLife International (2012). "Amblyramphus holosericeus". IUCN Red List of Threatened Species. Version 2012.1. International Union for Conservation of Nature. http://www.iucnredlist.org/apps/redlist/details/106009726. Retrieved 16 July 2012.
- Ridgely, Robert S.; Tudor, Guy (1989). The Birds of South America: The Oscine Passerines. University of Texas Press. pp. 345. ISBN 0-292-70756-8. http://books.google.com/books?vid=ISBN0292707568. Retrieved 2007-02-19.
- "Scarlet-headed blackbird". Meet the Animals. Toronto Zoo. http://www.torontozoo.com/Animals/details.asp?AnimalId=499. Retrieved 2007-02-19.
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