The horned sungem (Heliactin bilophus) is a species of hummingbird native to much of central Brazil and parts of Bolivia and Suriname.

The sexes differ markedly in appearance, with males sporting two feather tufts ("horns") above the eyes that are shiny red, golden, and green.

The horned sungem is a nomadic species, moving between areas in response to the seasonal flowering of the plants on which it feeds.

The species is currently classified as least concern by the International Union for Conservation of Nature, and its population is thought to be increasing.

The horned sungem was named as Trochilus bilophus in 1820 by the Dutch zoologist Coenraad Jacob Temminck.

This 1820 account only consisted of a figure plate illustrating a male specimen that was collected in 1816 by the German naturalist Prince Maximilian of Wied-Neuwied in Campos Gerais, Brazil.

[8] In 1921, the French naturalist Eugène Simon mistakenly assumed that Temminck's figure plate was published in 1824 instead of in 1820, and consequently considered Wied-Neuwied's name cornutus as the valid one, which was followed in most subsequent publications of the 20th century.

[11] Bilophus, rather than bilopha or bilophum, is correct despite the mismatch between its apparently masculine ending and the feminine one of the genus.

[10] "Horned sungem" is the official English common name designated by the International Ornithologists' Union (IOU).

[3] Within the Trochilidae (the hummingbird family), the horned sungem is a member of the subfamily Polytminae, which is also referred to as the "mangoes".

[12][13] The following cladogram based on genetic data shows the relationships of the horned sungem within the subfamily Polytminae:[12][13] Colibri-Group Horned sungem (Heliactin bilophus) Tooth-billed hummingbird (Androdon aequatorialis) Black-eared fairy (Heliothryx auritus) Purple-crowned fairy (Heliothryx barroti) Anthracothorax-Group The horned sungem is a small hummingbird with a long tail, measuring 9.5 to 11 cm (3.7 to 4.3 in) in length and weighing 1.8 to 2.8 g (0.06 to 0.10 oz).

[7] Each of these tufts consists of a row of six feathers that are inclined backwards and are fiery red at their base, golden in the middle, and golden-green at their tips.

The female, even though it lacks the unique adornments of the male, can be identified by its yellow-green upperside, its white underside, and its long tail.

[7][18] The horned sungem is found across much of central Brazil, in the east from southern Maranhão south to the north of the State of São Paulo and then west to western Mato Grosso and into Bolivia's Santa Cruz department.

[7] It has recently expanded its range into southern Amazonas and Espírito Santo, probably as a result of deforestation and its ability to adopt open landscapes created by humans.

[20] The horned sungem feeds on nectar from a variety of flowering plants, such as Palicourea rigida, Bauhinia tenella, Cuphea linarioides, Zeyheria montana, and Calliandra sincorana.

The "stiletto-shape" is pronounced in the horned sungem, although to a lesser degree than in some related hummingbirds such as Geoffroy's daggerbill, which is named after this feature.

Nectar robbing may be an important survival strategy for the horned sungem in times of food shortages.

It makes a small cup nest of soft material and spider web, adorned with lichen on the outside.

[1] A 2019 study estimated the vulnerability of 103 bird species native to the Brazilian Cerrado to changes in climate and land use projected for 2050, and found that the horned sungem is adaptable and comparatively insensitive to these threats.

Together with another hummingbird, the frilled coquette, the horned sungem had the highest estimated dispersal ability of the studied species.