A perfect fit

Ruby-throated Hummingbirds love red flowers.  In my garden, they particularly like the Cardinal Flower, which sends up 4 foot tall stalks with a bright red plume of flowers that develop sequentially from bottom to top of the stalk over a 4-6 week period. Apparently, it produces some really good nectar too, because it is the first flower they visit in the morning.

Here I come -- bring out the nectar.

Here I come — bring out the nectar.  This little female Ruby-throated Hummingbird was extremely cooperative, foraging for several minutes on a clump of cardinal flowers, while I sat in a very hot blind about 15 feet away.

Sometimes the probing is just a test to see what might be there, as the bird tastes with the tip of its tongue.

In this shot, her bill is inserted only part way into the flower, and her head is completely clear of the flower structures.

In this shot, her bill is inserted only part way into the flower, and her head is completely clear of the flower structures.  This foraging position won’t accomplish what the plant intended the bird to do in return for a nectar reward.

When there is sufficient nectar at the base of the flower, hummingbirds hover for several seconds in place while they mop up every drop.  In this case, the bird’s head almost disappears into the flower as it inserts the bill all the way in.

It looks like the hummingbird is getting a pat on the head from the flower.  In this case, the bird is indeed performing a vital service for the plant -- moving pollen from one flower to another.

It looks like the hummingbird is getting a pat on the head from the flower. In this case, the bird is indeed performing a vital service for the plant — moving pollen from one flower to another.

The bill of the Ruby-throated Hummingbird is the perfect size and shape for this flower.  When it dips its bill deep into the base of the flower, the top of its head brushes a fringe of anthers which deposit pollen on the surface of its head feathers.  Later when it visits a different flower, perhaps on a different plant, the pollen will be rubbed against that flower’s stigma, adhering to the sticky surface.  If it is the right type of pollen, it will germinate and a pollen tube will grow down the stalk supporting the stigma (the style) into the ovary. Sperm can then leave the pollen grain, swim down the tube, and fertilize the ova to begin the process of seed production.

The contact between the stigma of the flower and the

The contact between the stigma of the flower and the hummingbird’s head is more obvious in this close-up.

Hummingbirds don’t care which flowers deposit pollen on their head, but the plants want to ensure that a particular flower receives pollen from a different individual (i.e., avoid self-pollination).  To maximize the potential for out-crossing, Cardinal flowers develop the male parts first — promoting pollen donation, and after a few days, the style and stigma emerge to protrude beyond the anthers — promoting pollen reception.

The anthers look like a white fuzzy fringe on the stalk that sits above the petals and the opening of the flower.

The anthers look like a white fuzzy fringe on the end of a gray stalk that sits above the petals and the opening of the flower.  The flower on the left shows the pink stigma just beginning to grow beyond the level of the anthers.  The flower on the right is newer and does not yet have female reproductive parts showing.

A mature Cardinal flower, with the stigma (and style) protruding beyond the anthers.  This stigma could easily pick up pollen from the back of a hummingbird's head.

A mature Cardinal flower, with the stigma (and style) protruding beyond the anthers. This stigma could easily pick up pollen from the back of a hummingbird’s head.

Coevolution of cardinal flower structure and Ruby-throated Hummingbird sugar appetite has made this system a perfect fit for both.

The End.

The End.

16 thoughts on “A perfect fit

    • Oh that’s interesting. I have lots of hostas (some with flowers the deer haven’t eaten yet), but haven’t watched for hummingbirds on those. Supposedly cardinal flowers like damp places (like the giant lobelia), so I expect you have them there too??

  1. Yes, I have over 200 hostas in the yard and hummingbirds seem to love them. I haven’t seen any yet this year but they’re usually always around. We have cardinal flowers here and they grow near streams and rivers but I have a lot of trouble seeing them because of color blindness.

    • Unfortunately, no hummingbirds will stay here in the winter. (There are few bird species that stick out winter in Minnesota!) The hummingbirds will leave pretty soon for parts of Mexico, Central America, and the Caribbean. It’s amazing to think that this tiny little bird can migrate thousands of miles, sometimes clear across the open water of the Gulf of Mexico to northern South America.

  2. Wonderful post, Sue, with lots of great photos and information. Earlier this summer I looked carefully at the cardinal flowers when I photographed some tiny bees on them and read that hummingbirds pollinate the flowers. I couldn’t visualize how they accomplished that and your photos make it easier to understand now. The hummingbird shots are amazing–your time in the blind definitely paid off.

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