Melvin Grey / Variable sunbird (Nectarinia venusta) adult male on Hibiscus flower, Nairobi, Kenya

Ole Jorgen Liodden / Red-chested Sunbird (Cinnyris erythrocercus) backlit on flower, Rwanda.

Dong Lei / Mrs Gould's sunbird (Aethopyga gouldiae dabryii) male feeding from Chinese wild peach flowers (Prunus davidiana) Kawakarpo Mountain, Meri Snow Mountain National Park, Yunnan Province, China. May.

Dong Lei / Mrs Gould's sunbird (Aethopyga gouldiae dabryii) male hanging upside down and feeding from Chinese wild peach (Prunus davidiana) male blossom, Kawakarpo Mountain, Meri Snow Mountain National Park, Yun...

Richard Du Toit / Malachite sunbird {Nectarinia famosa} male feeding from flowers, South Western Cape, South Africa

Heather Angel / Malachite sunbird (Nectarinia famosa) male perching on King protea (Protea cynaroides) whilst foraging for nectar. Pearl Mountain Reserve, South Africa, August.

Heather Angel / Southern double-collared sunbird (Cinnyris chalybeus), male nectaring on Pincushion protea (Leucospermum cordifolium). Cape, South Africa. August.

Heather Angel / Malachite sunbird (Nectarinia famosa) male nectaring on King protea (Protea cynaroides). Pearl Mountain Reserve, South Africa, August.

Heather Angel / Southern double-collared sunbird (Cinnyris chalybeus), male nectaring on Pincushion protea (Leucospermum cordifolium). Kirstenbosch National Botanical Garden, Cape Town, South Africa. August.

Heather Angel / Malachite sunbird (Nectarinia famosa) male nectaring on King protea (Protea cynaroides). Cape Province, South Africa. August.

Heather Angel / Jade vine (Strongylodon macrobotrys) in glasshouse at Kew Gardens, London, UK. Endemic to the Philippines. Pollinated by sunbirds.

Heather Angel / Orange breasted sunbird (Anthobaphes violacea), male nectaring on Heather (Erica sp). Kirstenbosch Botanic Garden, Cape Town, South Africa. February

Jed Weingarten / Wild Wonders of China / Mrs Gould's sunbird (Aethopyga gouldiae) perched on branch, Tangjiahe Nature Reserve, Sichuan Province, China.

Ann & Steve Toon / Malachite sunbird (Nectarinia famosa) feding at flower, Kirstenbosch National Botanical Garden, Cape Town, South Africa, September

Ann & Steve Toon / Orange-breasted sunbird (Anthobaphes violacea) female on Leucospermum cordifolium 'Yellow Bird' Kirstenbosch National Botanical Garden, Cape Town, South Africa, September

Ann & Steve Toon / Orange-breasted sunbird (Anthobaphes violacea), Kirstenbosch National Botanical Garden, Cape Town, South Africa, September

Ann & Steve Toon / Southern double-collared sunbird (Cinnyris chalybeus), Kirstenbosch National Botanical Garden, Cape Town, South Africa, September

Ann & Steve Toon / Orange-breasted sunbird (Anthobaphes violacea) on flower, Kirstenbosch National Botanical Garden, Cape Town, South Africa, September

Ashish & Shanthi Chandola / Purple sunbird (Cinnyris asiaticus) on branch between flowers. Bandipur National Park, Nilgiri Biosphere Reserve, Karnataka, India.

Ashish & Shanthi Chandola / Purple sunbird (Cinnyris asiaticus) amongst orange flowers. Bandipur National Park, Nilgiri Biosphere Reserve, Karnataka, India.

Richard Du Toit / Greater double-collared sunbird (Nectarinia afra) at Cape honeysuckle (Tecoma capensis) flower, Garden Route National Park; South Africa; Western Cape Province; Wilderness

Richard Du Toit / Orange-breasted sunbird (Anthobaphes violacea) Western Cape Province, South Africa.

Richard Du Toit / Southern double-collared sunbird (Cinnyris chalybeus) on flowers, Western Cape Province, South Africa.

Richard Du Toit / Greater doublecollared sunbird (Nectarinia afra) on Wild Dagga (Leonotis leonurus) flowers. Garden Route National Park, Western Cape Province, South Africa.

Richard Du Toit / Southern double-collared sunbird (Cinnyris chalybeus) Garden Route National Park, Western Cape Province, South Africa.

Richard Du Toit / Grey Sunbird (Cyanomitra veroxii) on Wild Dagga (Leonotis leonurus) flowers, Garden Route National Park, Western Cape Province, South Africa.

Steven David Miller / Olive-backed sunbird (Nectarinia jugularis) female returning to her nest with nesting material, Cape Hillsborough National Park, Queensland, Australia, September.

Steven David Miller / Olive-backed sunbird (Nectarinia jugularis) female in her nest with tongue visible, Cape Hillsborough National Park, Queensland, Australia, September.

Steven David Miller / Olive-backed Sunbird (Nectarinia jugularis) female in her nest, Cape Hillsborough National Park, Queensland, Australia, September.

Steven David Miller / Olive-backed Sunbird (Nectarinia jugularis) male taking turns with his mate to bring nesting material to their nest, Cape Hillsborough National Park, Queensland, Australia

Steven David Miller / Olive-backed Sunbird (Nectarinia jugularis) A female olive-backed sunbird returns to her nest, Queensland's Cape Hillsborough National Park Australia

Steven David Miller / Olive-backed Sunbird (Nectarinia jugularis) male on a Hibiscus flower to feed, Rollingstone Beach, North Queensland, Australia. September.

Staffan Widstrand / Wild Wonders of China / Streaked spiderhunter (Arachnothera magna) bird perched on red flower in Hong Bung He, Dehong, Yunnan, China

Emanuele Biggi / Dusky sunbird (Cinnyris fuscus) feeding on the nectar of quiver tree (Aloidendron dichotomum) flowers, Aus, Namibia

Felis Images / Little spiderhunter (Arachnothera longirostra) perched on Torch ginger (Etlingera elatior) Kerala, India.

Felis Images / Fire-tailed sunbird (Aethopyga ignicauda) perched on conifer. Sikkim, India.

Ann & Steve Toon / Southern double-collared sunbird (Cinnyris chalybeus) singing, Kirstenbosch Botanical Gardens, Cape Town, South Africa, September.

Luis Quinta / Principe sunbird (Anabathmis hartlaubii) Island of Principe UNESCO Biosphere Reserve, Democratic Republic of Sao Tome and Principe, Gulf of Guinea.

Jurgen Freund / Olive-backed sunbird (Cinnyris jugularis) female tending chicks in her nest. Daintree , Queensland, Australia

Jurgen Freund / Olive-backed sunbird (Cinnyris jugularis) building nest, Daintree , Queensland, Australia

Nayan Khanolkar / Purple rumped sunbird (Leptocoma zeylonica) nest on string of fairy lights in Mumbai. India, August 2015.

Richard Du Toit / RF - Greater Doublecollared Sunbird (Nectarinia afra) male, Garden Route National Park, South Africa (This image may be licensed either as rights managed or royalty free.)

Richard Du Toit / Southern double-collared sunbird (Cinnyris chalybeus) on plant in fynbos, Western Cape Province, South Africa.

Richard Du Toit / Orange-breasted Sunbird (Anthobaphes violacea) male on protea flower, Garden Route, Western Cape Province, South Africa.

Richard Du Toit / Southern double-collared sunbird (Cinnyris chalybeus) Montagu Pass, Western Cape Province, South Africa

Richard Du Toit / Orange-breasted Sunbird (Anthobaphes violacea) Western Cape Province, South Africa.

Konstantin Mikhailov / Fire-tailed sunbird (Aethopyga ignicauda) male perched on sub -alpine Rhododendron bush, Central Himalaya, Mustang, Nepal, May

Ann & Steve Toon / Orange-breasted sunbird (Anthobaphes violacea) on flowers, Kirstenbosch Botanical Gardens, Cape Town, South Africa.