Cacicus haemorrhous haemorrhous

Exhibits a pronounced sexual size dimorphism, with adult males measuring between 27 and 30 centimeters in length, while females are significantly smaller, ranging from 22 to 25 centimeters. The plumage of this taxon is overwhelmingly a glossy black with subtle blue iridescence under direct sunlight, which contrasts sharply with a bright scarlet-red patch on the lower back and rump, normally concealed by the folded wings but highly conspicuous during flight. The bill is long, pointed, and has a distinct ivory-white to pale yellow-green coloration, contrasting with the striking bright blue eyes of mature individuals. Juvenile birds can be identified by their duller black plumage, brownish eyes, and darker, dusky bill.

Geographical distribution: Occupies a vast geographic range throughout the tropical lowlands of South America east of the Andes. Its distribution is split into two major core populations: one covering the extensive Amazon Basin across Brazil, Colombia, Peru, Ecuador, Bolivia, Venezuela, and the Guianas, and a disjunct, substantial population residing within the Atlantic Forest biome of eastern and southern Brazil, eastern Paraguay, and the northeastern corner of Argentina, particularly in the province of Misiones.

Habitat: Prefers humid lowland rainforests, gallery forests, mature secondary growth, and disturbed forest edges. It shows a strong affinity for ecotones and forested riparian corridors adjacent to open water sources, such as rivers, lakes, and marshes, where tall canopy trees provide both abundant foraging opportunities and secure nesting sites.

Feeding: Has an omnivorous diet, foraging dynamically in the forest canopy. It consumes a diverse array of wild fruits, berries, and nectar, which are supplemented by various invertebrates, including beetles, caterpillars, orthopterans, and spiders. It is a highly active forager, often searching for prey by probing curled leaves and dead wood in loud, monospecific or mixed-species flocks.

Behavior: Is exceptionally social and gregarious, remaining in active, noisy flocks throughout the year. Its vocalizations are incredibly varied and complex, consisting of metallic whistles, harsh chattering, and a remarkable aptitude for vocal mimicry of other avian species and environmental noises. During courtship, males perform dramatic physical displays, leaning forward, raising their wings, ruffling their brilliant red rump feathers, and emitting loud acoustic sequences to attract females.

Nesting: Breeds coloniously, establishing noisy and conspicuous nesting sites. The female constructs a long, pendulous, stocking-shaped pouch nest measuring between 30 and 60 centimeters in length, woven meticulously from flexible plant fibers, vines, roots, and bark strips. These nests hang from the tips of thin, downward-sloping branches of tall, isolated trees, frequently clustered in close proximity to active wasp nests of the genera Polistes or Synoeca to exploit the insects´ defensive behavior as a barrier against nest predators like capuchin monkeys and toucans. The typical clutch consists of two pale blue or white eggs speckled with brown, incubated solely by the female, although both parents actively feed the altricial chicks.

Conservation status: Is currently evaluated as Least Concern (LC) on the IUCN Red List of Threatened Species. The species remains common to abundant throughout most of its extensive distribution, demonstrating a degree of resilience to moderate forest fragmentation, although localized populations face long-term risks from habitat degradation and deforestation within the Amazonian and Atlantic Forest biomes.