Most tropical rainforest plants rely upon animals for pollination. The lack of wind in tropical rainforests and the greater distance between individuals of a plant species are two factors that make wind pollination inefficient. Insects, birds and mammals pollinate these tropical plants inadvertently by transferring pollen from flower to flower in their quest for nectar or pollen. Bird pollination is found throughout the world with the exception of Europe and Asia north of the Himalayas. It occurs most commonly, however, in the tropics.
Hummingbirds are an important groups of bird pollinators.
Hummingbirds are found only in the Americas. Flowers pollinated by birds are usually brightly colored in reds, oranges or yellows. The flowers are held away from the foliage, produce copious, watery nectar and are often more strongly constructed to support the weight of the bird. Most bird-pollinated flowers are odorless as birds lack a good sense of smell. Some flowers are pollinated by bees.