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| Male Antillean Crested Hummingbird piercing a Ginger Thomas flower |
When I noticed several Antillean Crested Hummingbirds flitting around the Ginger Thomas flowers I thought, how sweet, they are busy pollinating the flowers. But no!
I went to get my camera, and took some shots with my telephoto lens. At a distance I hadn’t been able to see exactly what the birds were doing, but when I looked at the photos in my computer I was shocked.
They weren’t even thinking about pollinating the flowers! These birds were entirely bypassing the insides of the trumpet-shaped flowers, where the female stigmas were waiting patiently to receive male pollen grains that would fertilize them.
Instead the hummingbirds were staying outside and sticking their sharp beaks into the flower bottoms, sucking out the sweet liquid directly from the nectar sac.
Flowers produce nectar to provide an enticement and reward for visitors that then pick up pollen (often inadvertently) and transport it from one flower to another. Food in exchange for cross-pollination services. Not a free lunch.
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| A female Antillean Crested Hummingbird is lighter and lacks the crest. |
Self-pollination by a flower leads to lack of genetic diversity, with diminished strength and adaptability of the resulting seeds and seedlings. Like many other trees, a Ginger Thomas (Tecoma stans), also known as Yellow Trumpetbush, makes an effort to avoid self-pollination. One measure, for example, is to set different times of day for pollen dispersion and stigma receptivity within a flower, so self-pollination can’t happen by mistake.
The Ginger Thomas really wants the birds and bees to come and bring outside pollen into contact with the flower’s inner reproductive parts. The flower uses its bright yellow color and an enticing scent to attract potential pollinators. How frustrating then for the flowers to instead be poked, probed, and robbed of their laboriously made sweet fluids with nothing to show for it.
In defense of the Antillean Crested Hummingbirds, the issue might be that their bills are too short – maybe only half an inch – so they can’t reach the nectar sac by going through the natural flower opening, which is narrow, and can be two inches deep. Then again, hummingbirds also have long tongues that are designed to extend way out past their bills to allow them to reach deep inside tubular flowers.
Maybe it’s just easier to break in.
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Antillean Crested Hummingbirds hover with up to 80 wing beats per second. |
Interestingly, although Ginger Thomas has been designated as the official flower of the U.S. Virgin Islands, there is some question about whether it is actually native in these islands. So perhaps it is unfair of me to accuse the crested hummingbirds of violating some ancient coevolution pact in this relationship.
Other common local hummingbirds, the Green-throated Caribs, don’t seem to have any trouble reaching inside the Ginger Thomas flowers and performing pollinator duties. They are larger and have longer, curved bills. Probably also longer tongues.
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| Green-throated Carib hummingbirds are larger, and don't steal the nectar. |
I also saw Bananaquits exploring the Ginger Thomas flowers. They are known as ‘Sugar Birds’, so of course they would be attracted to the sweet nectar. But they certainly don’t have the right type of bill to slip inside the elongated Ginger Thomas flowers.
From watching the Bananaquits, though, I know that they too have long tongues, which they sometimes use to drink from hummingbird feeders.
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| Bananaquits have long tongues too. |
Meanwhile, it’s not only birds that are nectar robbers. Bees do it too!
A few big, shiny black Carpenter Bees came to the Ginger Thomas flowers and went straight for the flower ends. These are native solitary bees – they don’t live in hives with other bees. They are called ‘carpenters’ because they bore holes in tree branches and other wood to make nests. Then they place ‘bee bread’ made out of pollen and nectar in the nests with their eggs to provide food for the emerging larvae.
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| Female carpenter bee and Antillean crested hummingbird |
Too bulky to crawl inside Ginger Thomas flower, a Carpenter Bee can use its sharp, wood-cutting mandibles to make an incision at the base of the flower. Then it can suck up nectar from the hole through its straw-like tongue or proboscis, which clearly isn’t long enough to reach down inside the Ginger Thomas flower. Or it might go to a hole already made by a bird to mop up any leftover nectar seeping out.
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| Carpenter bee poking Ginger Thomas flower |
European Honeybees come to the Ginger Thomas flowers too. They were brought here to pollinate crops, but they will go to wild trees as well (sometimes reducing nectar availability for native bees). A honeybee will crawl in and out of different flowers, drinking nectar through its proboscis. Meanwhile, it is also collecting pollen in sacs on its legs and transferring some of it to other flowers, thereby facilitating pollination.
But a honeybee might instead use an already-made hole to suck up nectar, as will other possibly pollinating insects, like ants and wasps.
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| Honeybee crawling on Ginger Thomas |
It turns out that nectar robbing is actually pretty common behavior. Too much thieving from flowers could significantly reduce the ability of trees to get pollinated. Or cause hardship to other would-be pollinators that lose out on going to those flowers and getting nectar as a food source.
Yet the Ginger Thomas trees seem to be thriving, despite all the nectar robbing. On the other hand, the Antillean Crested Hummingbirds became pretty scarce after the 2017 hurricanes, and still might need some extra resources.
Perhaps the Ginger Thomas trees have adapted their nectar production to take the skimming into account. Or are actually being generous in feeding the neighborhood birds and bees, and would characterize these interactions as interspecies generosity rather than robbery.
