By Sam Burbach, Education & Programming Coordinator – 06/26/2020
We most often associate insects with pollination, but there’s a number of vertebrates who also help pollinate our flowering plants. The first we might think of is hummingbirds, which is true, but in the air there are other bird species and even bats who are also provide pollination services!
Bird pollination, or Ornithophily, is a result of birds seeking out nectar deep within a flower as a high-energy drink source to replenish the high number of calories birds burn from flying. There are about 2,000 species of pollinating birds, according to the U.S. Forest Service, and most of this ornithophily occurs in tropical regions, although there are some birds who help with pollination in our region. Pollinating birds in the U.S. primarily help pollinate wildflowers, whereas bird pollinators in tropical regions also contribute to the pollination of food crops, such as wild bananas, papaya, and nutmeg.
Pollinating birds are attracted to flowers usually in the warm range of the ultra-violet spectrum, except for yellow, with red, orange, and purple hues being favorites. Birds do not have a strong sense of smell, so flowers do not need to have a strong fragrance to attract the birds. Instead, flowers pollinated by birds need an ample supply of nectar since the birds are looking for larger quantities of it than insects. The nectar is generally held deep within the flower, often with the flower forming a tube shape, so that the bird has to reach its beak deep within the flower to retrieve it thus brushing its body up against the anthers and pollen supply. Not all birds are able to hover while they drink the nectar, so flowers that rely on non-hovering birds need to have a strong support for perching.
Some flowers have adapted to provide a strong perch for bird pollinators, such as Bird of Paradise. In South Africa, Bird of Paradise is pollinated primarily by Cape Weavers who do not hover while they feed on the nectar. Instead, they stand on the blue petals which open to expose the pollen under the bird’s weight. As the cape weavers stretch their beaks to reach the nectar deep within the flower their bodies brush up against the pollen which they will inevitably carry with them to the next flower. Since these birds are only found in South Africa, Birds of Paradise that are grown as ornamental plants in places like California or Florida usually go unpollinated due to lack of the flower’s primary pollinator.
Hummingbirds are the most popular and most hard-working bird pollinators in our area. There are over 330 species of hummingbirds and all are native only to the Americas. The Ruby-throated Hummingbird is the only consistently found hummingbird species in the Eastern U.S. and Canada, and in Illinois we are lucky enough to have these visitors each summer and be included in their breeding range. Hummingbirds hover while they feed so the flowers they visit do not need sturdy stems or landing perches. Hummingbirds reach their long beak and tubular tongue deep within tube-shaped flowers and inadvertently brush their bodies up against the pollen which sticks to their feathers. It is estimated that hummingbirds will visit an average of 1,000 flowers each day to drink enough nectar to support its fast metabolism. That is a lot of pollination!
Photograph by Craig Michelsen
Geothlypis trichas (common yellowthroat), a warbler family member, perches on a mechanically reinforced anther sheath formed by fused petals of the Bird of Paradise flower (Strelitzia reginae).
(Photograph by South African Journal of Botany, Wagner, 1894)
Bats are not often associated with pollination, and that can be understandable since most bats are nocturnal meaning they are active at night when we usually don’t notice them. With that being said, bat pollination, or Chiropterophily, is very important because bats pollinate flowers that open at night time. Most bat pollination occurs in tropical and desert climates. There are over 500 plant species that rely on bat pollination, including food crops such as wild bananas, mangoes, guava, and agave. In the U.S., bats are critical pollinators in the desert areas of the Southwest, pollinating agave plants, saguaros, and various other cacti. In our region, bats may help pollinate flowers such as moonflowers, evening primrose, yucca, and four o’clocks. Bats prefer flowers at least 1-inch across that are typically white or pale colored, have an ample amount of nectar, and are very fragrant, usually having a fruity or fermenting scent.
Bats make great pollinators because, as mammals, they are covered in hair. As bats reach into flowers to drink the nectar, their faces and bodies get covered in pollen. Due to a size of a bat compared to an insect and the amount of fur they are covered with bats can transport more pollen than their insect pollinator counterparts. They can also fly considerably further than most insects increasing the range they pollinate.
Watch bat pollinators in action in this short DisneyNature video: https://vimeo.com/63694877
(Photograph by U.S. Department of Agriculture)
(Photograph by Merlin D. Tuttle, BCI)