Word of the day: Ornithophily — or obligate pollination by birds, and typically by hummingbirds. Last summer, I wrote about the coevolutionary “perfect fit” of Ruby-throated Hummingbirds and Cardinal flowers.
As the hummingbird dips its beak into the long flower tube, the top of its head picks up pollen from the flower’s anthers. The male (anther) parts of the flower are first to project from a new flower. A day or two later, the anthers fold down and the female (stigma) projects from the flower tube to receive pollen from younger flowers. In this way, the plant ensures that it gets cross-pollinated. See Back Yard Biology, Aug 17, 2013/
Plants that depend on birds for pollination typically provide much higher volumes with higher sugar content of the nectar than insect-pollinated flowers. In contrast, insect-pollinated flowers tend to be heavily scented but have meager nectar with low sugar content. So it’s no wonder so many insects find ways to enjoy the riches of bird-pollinated flowers without performing the vital pollination service.
A large clump of Scarlet or Crimson Beebalm in my garden, with its ornithophilous flowers, awaits its pollinators — the Ruby-throated Hummingbirds.
Honeybees (but there was only one in the garden) land on the lower part of the flower and climb into the long tube to reach the nectaries at the base of the corolla. Their slender bodies fit perfectly into the floral tube, completely avoiding the anthers and stigma projecting from the flower.
Side view of the same approach by the honeybee as it walks into the flower tube. The Y-tipped stigma and lobe-shaped anthers are clearly far away from the dorsal surface of the bee.
This bee had a good long drink of nectar in this flower before moving on.
Even the bumblebee tried getting some of that rich sucrose each flower in the cluster provides. However, the bumblebee’s chunkier body didn’t permit it to actually crawl into the flower. Some Bumblebee species have a long hairy tongue that helps them reach deep into the flower. I don’t know if this is one of those species.
I think Bumblebees might also have a different strategy to harvest nectar from flowers they are too large to crawl into. Its body weight is enough to pull the flower down and allow nectar to flow down the floral tube toward the opening where the bee could lap it up.
Bumblebees might be large enough to contact the anthers and/or stigma as they try to crawl into the flower. At least that’s what it looks like in this photo.
Another nectar thief, the Clearwing Hummingbird Moth also enjoys the rich nectar of Scarlet Beebalm without coming close to contacting the flower’s reproductive parts. Photo by Kate St. John.
Ornithophily has its risks. If birds don’t find the flowers or weather throws off the timing of the arrival of the birds and flower blooms, the plants risk not getting pollinated at all. But in the case of the beebalm flowers, bumblebees might be able to make up for the lack of bird pollinators by transferring some pollen. Why else would they call it bee-balm, and not bird-balm?