The Principe Sunbird is a small, restless nectar-feeder found nowhere on Earth except Principe Island, the smaller of the two main islands that make up the nation of Sao Tome and Principe in the Gulf of Guinea, off the coast of Central Africa. Like sunbirds everywhere, it lives at a fast pace, darting between blossoms, hovering briefly, and probing flower after flower with its fine, downcurved bill to reach the nectar inside.
It belongs to Anabathmis, a small genus of Gulf of Guinea sunbirds, and honors the nineteenth-century German ornithologist Gustav Hartlaub, whose name survives in the scientific epithet hartlaubii. In the right light the male catches the sun in flashes of metallic green and bronze, while the female is a modest olive bird that is easy to overlook. Because Principe has so few resident land birds, this sunbird stands out as one of the island's most characteristic and easily seen species, common from coastal gardens and cocoa plantations up into the forested interior. For visiting birders it is a near-guaranteed and delightful island endemic.
Identification on Principe is refreshingly simple: this is the island's only resident sunbird, so a small bird with a slender, downcurved bill feeding at flowers is almost certainly this species. The challenge is not telling it from other sunbirds but simply telling males from females and appreciating the metallic colors, which only show well when direct light strikes the plumage. In shade the male can look surprisingly dark and dull.
| Size | A small sunbird about 13 to 14 cm long, slim and long-tailed in shape |
| Bill | Slender, sharply downcurved and adapted for probing deep into flowers |
| Male upperparts | Iridescent metallic green to bronze, catching the light on head and back |
| Male underparts | Bright yellow belly, often with tufts of yellow feathering at the sides of the breast |
| Female | Much plainer, olive-green above and pale yellowish below, without strong iridescence |
| Range clue | The only sunbird resident on Principe Island, so range alone nearly clinches it |
Male vs. female
The sexes are noticeably different, which is typical of sunbirds. The male is the showy one, with upperparts that shimmer metallic green and bronze in sunlight, a glossy head, and a clean bright-yellow belly. Tufts of yellow feathers at the sides of the breast, often hidden, can be flashed during display or squabbles at a flowering tree. The female is far more subdued: olive-green above and washed pale yellow below, lacking the male's metallic sheen. Seen alone she is best identified by her small size, slim shape, and thin downcurved bill, plus the simple fact that she is the only sunbird on the island. In poor light even a male can look drab, so patience for a shaft of sun often transforms a dull bird into a glittering one.
Juveniles
The breeding biology of this species is poorly documented, and young birds are correspondingly little described in the literature. As in related sunbirds, juveniles can be expected to resemble the dull female, olive-toned and without the male's iridescence, with young males only gradually acquiring metallic feathering as they mature. Because so few detailed field observations exist for Principe specifically, it is honest to say that the exact sequence of immature plumages here is not well established, and any small, plain sunbird on the island is safely identified simply by its range.
Like most sunbirds the Principe Sunbird is vocal and easy to hear before it is seen. It gives high, thin, tinkling notes and quick, twittering phrases as it works through flowering foliage, along with sharp, insistent call notes. These calls come thick and fast during disputes, when one bird chases another away from a favored flowering tree. The overall impression is of a busy, high-pitched, metallic chatter rather than a rich musical song. Detailed studies of its vocal repertoire are limited, so descriptions rest mainly on the thin, tinkling and scolding notes that field observers consistently report.
The Principe Sunbird is endemic to Principe, a single volcanic island of roughly 140 square kilometers in the Gulf of Guinea. It is not found on neighboring Sao Tome, on the Central African mainland, or anywhere else, which makes its entire world range one small tropical island.
Within Principe it is widespread and adaptable, occupying lowland primary and secondary forest, forest edges, gardens, and the shade plantations of cocoa and coffee that cover much of the island. It ranges from coastal lowlands up into the rugged, forested interior and the dramatic volcanic peaks of the island's south. Being a permanent resident on a small equatorial island, it does not migrate; instead its movements are local, tracking whichever trees and shrubs happen to be in flower. This flexibility across both wild forest and human-altered habitat is a large part of why it remains common despite its tiny geographic range.
Nectar is the foundation of the diet. The sunbird visits a wide variety of flowering plants through the day, using its fine downcurved bill and tube-like tongue to draw nectar from blossoms, often clinging acrobatically or hovering briefly at a flower. In doing so it acts as a pollinator, moving pollen between the plants it feeds on.
Nectar alone cannot supply enough protein, so the bird also takes small insects and spiders, gleaned from leaves and bark or snatched from the air in short sallies. This animal prey is especially important during breeding, when growing nestlings need protein-rich food. The mix of sugar-rich nectar and small invertebrates is standard for sunbirds and lets the species exploit both flowering trees and the insect life of Principe's forests and plantations.
Breeding is not well documented for this island endemic, and much of what can be said is inferred from the habits of closely related sunbirds. By that pattern it is expected to build a small, enclosed, purse-shaped nest woven from plant fibers, fine grasses, and other soft material, suspended from a slender twig or hanging vegetation, often with a side entrance and a hooded top. In sunbirds generally the female does most or all of the nest construction and incubation, while both parents may help feed the young.
The clutch is thought to be small, on the order of one or two eggs, consistent with tropical sunbirds. Precise details of the laying season, incubation period, and fledging time on Principe remain poorly known, and further field study would be needed to confirm them. It is more honest to acknowledge these gaps than to fill them with figures borrowed uncritically from mainland species.
You will not attract this bird to a backyard feeder, because its whole world is one island in the Gulf of Guinea. For almost everyone, seeing a Principe Sunbird means traveling to Principe itself. The good news is that once you are there it is one of the easiest of the island's endemics to find, and no seed or special effort is required, just time in the right habitats.
- Travel to Principe Island, part of Sao Tome and Principe; the sunbird is not found on Sao Tome or anywhere else, so the island is the destination.
- Watch flowering trees and shrubs anywhere on the island; the bird follows the bloom, so any tree in heavy flower is a natural magnet.
- Bird the cocoa and coffee plantations and forest edges around towns and lodges, where the species is common and easy to see at close range.
- Explore into the forested interior and the volcanic peaks of the south, ideally with a local guide, to combine it with Principe's rarer endemics.
- Look and listen in the early morning, when sunbirds are most active at flowers and their thin, tinkling calls carry well.
- Position yourself for good light, since the male's metallic green and bronze only glow when the sun strikes the plumage directly.
- Newton's Sunbird: Sunbird of nearby Sao Tome, filling a similar role on that island
- Sao Tome Sunbird: Larger Gulf of Guinea sunbird endemic to neighboring Sao Tome
- Olive Sunbird: Plain mainland African sunbird of similar size and bill shape
Where does the Principe Sunbird live?
It is endemic to Principe Island, the smaller main island of Sao Tome and Principe, in the Gulf of Guinea off the coast of Central Africa. It occurs nowhere else in the world, not even on neighboring Sao Tome.
What does the Principe Sunbird eat?
Mainly flower nectar, gathered from many flowering plants with its slender downcurved bill. It also takes small insects and spiders for protein, which matters most when feeding young.
How do you recognize the male?
The male shows iridescent metallic green and bronze upperparts that flash in sunlight, plus a bright yellow belly and often hidden yellow tufts at the sides of the breast. In shade he can look surprisingly dark.
How is the female different from the male?
The female is much plainer, olive-green above and pale yellowish below, without the male's metallic sheen. On Principe she is easily identified anyway, since it is the island's only resident sunbird.
Is the Principe Sunbird endangered?
No. Despite living on a single small island, it remains common across forest, gardens, and plantations, and is currently classed as Least Concern. Its restricted range still makes long-term habitat protection on Principe important.
How can I see a Principe Sunbird?
You need to visit Principe itself. Once there it is one of the most reliable endemics, common around flowering trees, plantations, and forest edges, and easiest to enjoy on a sunny morning when the male's colors shine.