Sunbird Diversity East Africa 2027: the Hummingbirds of the Old World and the Nectar Guild
The sunbirds [family Nectariniidae] are the East African ornithological circuit’s “hummingbird equivalent” — the 30 to 45 sunbird species present in the Tanzania and Kenya safari ecosystems [depending on the altitude range and the habitat breadth of the itinerary] being the most diverse nectar-feeding bird family in the Afrotropical region. The East African safari visitor on the standard Tanzania-Kenya savannah circuit encounters 8 to 15 sunbird species on a 7 to 10 day trip [the number increasing to 20 to 30 species for the itinerary that adds the highland forest zones — the Aberdare National Park, the Bwindi-adjacent Buhoma forest in Uganda or the Usambara Mountains’ forest circuit]. The sunbird’s convergent evolution with the hummingbird: the sunbirds are the Old World’s convergent equivalent of the New World hummingbirds [the same ecological function — the principal flower-visitor and the primary pollinator of the nectar-producing plants] but achieved through entirely different anatomy [the hummingbird hovers at the flower using the independently rotating shoulder joint that generates the figure-8 wingbeat, the sunbird perches at the flower using the curved bill to access the nectary from the perch position — the sunbird cannot hover except for the 1 to 3 second “hover-sip” at flowers without a suitable perch] and different evolutionary origin [the sunbird’s ancestor from the warbler-like Passeriformes versus the hummingbird’s ancestor from the swift-like Apodiformes]. The 5 most distinctive East African sunbird species for the 2027 safari visitor: the superb sunbird [Nectarinia superba — only in Uganda, not in Tanzania-Kenya, notable here for context]; the variable sunbird [Cinnyris venustus — the most widespread and most frequently encountered sunbird in both Tanzania and Kenya’s savannah zone, the adult male’s black-and-white-yellow iridescent plumage the most immediate sunbird sighting on every game drive]; the Marico sunbird [Cinnyris mariquensis — the dry acacia zone’s primary sunbird, the Samburu, Tsavo East and the Serengeti’s northern dry zone’s characteristic sunbird at the Acacia tortilis and Salvadora flowers]; the malachite sunbird [Nectarinia famosa — the East African highland’s most spectacular sunbird, the adult male at 26 to 28 centimeters total length [the longest-tailed sunbird in Kenya and Tanzania] with the brilliant iridescent emerald-green plumage and the 10 to 14 centimeter tail-streamers, found in the highland zones above 1,800 meters in the Aberdare National Park, Mount Kenya and Ngorongoro rim’s alpine zone]; and the scarlet-chested sunbird [Chalcomitra senegalensis — the most dramatically bicolor sunbird in the savannah zone, the male’s velvet-black plumage with the brilliant red breast patch at the Acacia and Erythrina flowers].
Sunbird Feeding Ecology: Bill Morphology, Nectar Theft and the Plant Mutualism
The sunbird’s primary food is floral nectar [70 to 85 percent of the diet by caloric intake] supplemented by arthropods [the arthropod component providing the protein and fat that the nectar’s carbohydrate-only energy source cannot provide, particularly critical during the breeding season’s protein-demanding chick-rearing phase]. The bill morphology: the sunbird’s curved bill is the primary adaptation for the nectar-feeding from the tubular or cup-shaped flowers of the Leonotis nepetifolia [lion’s-ear, the most-visited savannah flower by the variable and marico sunbirds], the Aloe species [the red-yellow aloe spike, the primary source for the malachite sunbird in the highland zone and the bronze sunbird at the mid-altitude forest margin], the Erythrina species [the coral tree’s red flower, the most visited sunbird-flower in the East African forest margin], and the Acacia tortilis flower [the small, round cream flower cluster of the umbrella thorn acacia, visited by the Marico sunbird during the Acacia’s March to May and August to October flowering seasons]. The nectar theft: the sunbird’s bill morphology — though generally well-matched to the primary flower’s corolla length — produces the “nectar theft” behavior when the sunbird encounters a flower whose corolla is too long for the bill to reach the nectary from the flower’s entrance: the sunbird punctures the base of the corolla with the bill [the “base puncture theft”] accessing the nectary from the outside [the puncture not transferring the pollen and thus providing no pollination service to the flower — a pure parasitism of the mutualism]. The sunbird’s territorial behavior: the sunbird maintains a “nectar territory” [the feeding territory centered on the highest-density flowering shrub or tree in the bird’s home range, defended against other sunbirds, the white-eyes [Zosterops species] and the smaller honeyeaters by the “chase display” — the rapid aerial chase at 40 to 55 km/h that the territorial sunbird initiates within 3 to 8 seconds of the intruder’s appearance at the defended flower]. The malachite sunbird’s highland territory: the malachite sunbird’s territory in the Aberdare National Park and Mount Kenya’s giant heather zone [3,000 to 4,200 meters altitude] centers on the giant lobelia [Lobelia telekii] and the giant groundsel [Senecio keniodendron] flowering spikes, the territorial male defending the single most productive lobelia spike [often a single spike producing 2 to 5 milliliters of nectar per day] against rival males for the 3 to 5 week flowering duration of the individual spike.
Sunbird Breeding: Nest Architecture, the Hanging Bag and the Male Display
The sunbird’s nest is the most architecturally elaborate nest of any East African bird family — the female’s pendant [hanging] nest [the oval or pear-shaped nest suspended from the end of the finest branch available, the nest’s thin “stalk” [the 5 to 15 centimeter thread-nest junction] too thin for any climbing predator to cross] is constructed from the spider web [the primary structural material, providing the elasticity and the camouflage adhesion of the external surface], grass, plant fibers and the “porch” [the projecting roof extension that deflects rain from the entrance hole in the lower third of the nest’s body — the sunbird’s most architecturally distinctive nest feature, shared with the weaver-bird family but absent in every other East African passerine]. The nest building: the female builds the nest solo [the male provides no nest-building assistance in any of the East African Nectariniidae species studied to date], the construction period at 7 to 15 days [the variable and marico sunbird, the most common nest-builders], and the completed nest at 8 to 15 centimeters in length with the entrance hole at the lower third’s lateral position [the side entrance hidden by the porch extension]. The male’s display: the male sunbird’s iridescent plumage display [the iridescent feathers’ structural coloration [the thin-film interference from the flat, spatula-shaped barbule cells that produce the color by wavelength-selective reflection rather than pigment] producing the iridescent flash visible at 20 to 80 meters only at the correct observation angle — the male’s breast-puffing display [the breast feathers erected to maximum area, the bird’s body rotated to the angle that maximizes the iridescent flash toward the female or rival] is the primary sexual selection signal, the female selecting the male with the most intense and most consistent iridescent display as the breeding partner. The sunbird’s contribution to East African plant ecology: the sunbird guild’s combined pollination services to the Acacia, Aloe, Leonotis, Erythrina and Lobelia species in Tanzania and Kenya are estimated [the 2019 Afrotropical Pollination Ecology review] at 60 to 80 percent of the total pollination of these 5 plant genera in the sub-Saharan African range — the sunbird’s loss from any ecosystem would produce the reproductive failure of 40 to 60 percent of the nectar-dependent plant species in that ecosystem, with cascading effects on the frugivore community and the seed dispersal network.
Best Sunbird Viewing 2027: the Garden, the Forest Edge and the Highland Zone
The 2027 sunbird viewing guide for Tanzania and Kenya: the sunbird is the most easily viewed and most actively photographable of all the East African small birds — the perching behavior [unlike the flycatcher or the warbler’s rapid movement through the vegetation], the bright iridescent plumage [visible at 5 to 30 meters in direct sunlight, the iridescent blue-green-purple-red of the male’s breeding plumage one of the most saturated colors in the East African bird palette], and the predictable flower-visiting behavior [the sunbird returning to the same Aloe or Leonotis spike at 15 to 45 minute intervals throughout the morning] make the sunbird the most “stationary and predictable” small-bird photography target in the East African circuit. Tanzania’s best sunbird sites 2027: the Ngorongoro Crater rim’s forest zone [the Ngorongoro Serena Safari Lodge and the Ngorongoro Crater Lodge’s garden — the highland garden’s planted Aloe, Leonotis and Erythrina attracting the malachite sunbird, the bronze sunbird [Nectarinia kilimensis] and the tacazze sunbird [Nectarinia tacazze] to the hotel garden’s veranda-viewing flower beds, the easiest sunbird photography in Tanzania]; the Arusha National Park’s Momella Lakes area [the bird-list at 600+ species with the 8 to 12 sunbird species of the 1,500 to 1,800 meter altitude zone accessible on the park’s guided walks]; and the Kilimanjaro forest zone [the montane forest circuit at 1,800 to 3,000 meters on the Marangu and Machame routes’ lower slopes, the 8 to 12 sunbird species of the forest zone accessible to the non-climber on the forest-zone day-walk program from the Kilimanjaro Mountain Cottages or the Kibo Palace Hotel]. Kenya’s best sunbird sites 2027: the Lake Nakuru National Park [the acacia woodland surrounding the flamingo lake supporting 9 to 14 sunbird species including the scarlet-chested, variable and beautiful sunbirds at the Acacia tortilis canopy, the most consistent sunbird diversity of any Kenya national park in the Rift Valley circuit]; the Samburu-Buffalo Springs Reserve [the Marico sunbird’s highest density in Kenya at the Ewaso Ng’iro River’s Acacia and Salvadora thicket, the most reliable Marico sunbird photography in Kenya at the Samburu Game Lodge’s river-bank vegetation]; and the Aberdare National Park [the malachite sunbird’s most spectacular display-ground at the giant lobelias of the moorland zone [3,000 to 3,800 meters], accessible from the Ark and the Aberdare Country Club’s moorland drive].