Birds as pollinators
Pollination, whereby pollen grains (male) are transferred to the ovule (female) of a plant, is an irreplaceable step in the reproduction of seed plants. Most plant fruits are unable to develop without pollination taking place and many beautiful flower varieties would die out if not pollinated. Bees and insects are the most common pollinators, but bats and birds are known to do their share in this vital activity. The agent moving the pollen, whether it is moths, bees, bats, wind or birds, is called the “pollinator” and the plant providing the pollen is called the “polliniser”. Biotic pollination is the term used when pollination is aided by a pollinator. When this is carried out by birds, the term used is Ornithophily. Hummingbirds, spider hunters, sunbirds, honeycreepers and honeyeaters are the most common pollinator bird species. Plants that make use of pollination by birds commonly have bright red, orange or yellow flowers and very little scent. This is because birds have a keen sense of sight for colour, but generally little or no sense of smell. Bird pollinated flowers produce copious amounts of nectar to attract and feed the birds that are performing the pollination, as well as having pollen that is usually large and sticky to cling to the feathers of the bird. Hummingbirds are small birds which are found only in the Americas. Their ability to hover in mid-air by flapping their wings up to eighty times per second, plus their long curved beaks and a love for sweet nectar, makes them perfect pollinators. Hummingbirds burn up a tremendous amount of energy as they dart about from flower to flower and so they are attracted to the flowers that will give them something in return for their pollinating efforts. The flowers they are particularly fond of include shrimp plants, verbenas, bee balm, honeysuckles, fuchsias, hibiscus and bromeliads. Sunbirds and spider hunters feed mainly on nectar, although when feeding young, they often also eat insects. Sunbird species can take nectar while hovering, but usually perch to feed. Their long curved beaks and brush-tipped tubular tongues make these birds particularly suited to feeding on and pollinating tubular flowers. Honeyeaters resemble hummingbirds in many ways, but are not capable of lengthy hovering flight. Honeyeaters quickly flit from perch to perch, stretching or hanging upside down in order to reach the nectar with their highly developed brush-tipped tongue, while at the same time serving as a pollinator. Birds are not known for pollinating food growing crops, but this does not mean that they are not important. If it were not for the assistance of our feathered friends, many plant species would be in danger of extinction. Attained from: http://www.birds.com/blog/the-important-role-of-birds-in-pollination/ on 20th Nov, 2012.
Globally, bird-pollinated plants can be separated into two groups, one consisting of species pollinated by specialist nectarivores, and the other of plants pollinated by occasional nectarivores. There are marked differences in nectar properties among the two groups, implying that there has been pollinator-mediated selection on these traits. This raises the possibility that variation in bird assemblages among populations of a plant species could lead to the evolution of intraspecific variation in floral traits. We examined this hypothesis in Kniphofia linearifolia, a common and widespread plant in southern Africa. Although bees are common visitors to flowers of this species, exclusion of birds from inflorescences led to significant reductions in seed set, indicating that the species is primarily bird-pollinated. We showed that bird pollinator assemblages differ markedly between five different populations of K. linearifolia, and that variation in flower morphology and nectar properties between these populations are associated with the dominant guild of bird visitors at each population. We identified two distinct morphotypes, based...
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