the “good morning” hummingbird

What could be more pleasant than to sit outside on a coolish, bright sunny morning with a cup of coffee and a camera watching Ruby-throated Hummingbirds forage on Salvia flowers? The light was harsh and full of high contrast until the birds visited just the right flowers…

Salvia flowers are the right color, the right depth for the hummingbird’s bill and tongue, and the right fit for its head to pick up pollen from the flower’s protruding anthers.

Peek-a-boo, it looks like the hummer is keeping an eye on me while I’m keeping an eye on it.

I never get tired of watching their acrobatic flights between flowers as they probe each one for the tiny bit of nectar at the bottom of each floral tube.

Soon these tiny bundles of energy will undertake a giant-sized migration south to the Gulf coast. There they will again stock up on sugar-rich nectar to convert to fat stores that supply the energy for them to cross the Gulf of Mexico (the smallest birds to do so), without stopping, to get to their overwintering sites in Central America.

Because of their high requirement for sugar during their migration, they become frequent visitors to backyard nectar feeders at this time of year. To keep these little dynamos healthy on migration, remember to change the sugar solution in your feeders every 3-4 days, so it doesn’t grow mold or bacteria.

it’s not always a perfect fit

While waiting for the hummingbirds to show up to have their photos taken last week, I got plenty of time to watch some insect pollinators in action.  Some plants are obviously not fussy about what or how many pollinators they attract, so they put out a vast array of flowers — like a buffet table.

Black-eyed Susans and Purple Coneflower put their pollen and nectar up for grabs on the tiny disc flowers at the center of the flower. All comers are welcome to partake here — in this case, a Tiger Swallowtail was dipping its long proboscis carefully into each of the tiny openings of the disc flowers.

But some plants are fussier about which pollinator they cater to and which they can physically exclude.  It was amusing to watch several different bee species work the plants with tubular flowers, especially the ones with deep necks, like Salvia and Bee Balm.

A slender honeybee fits just perfectly into the deep corolla of a Salvia plant, as it crawls down to the base where the nectar is located.  Bumblebees would not fit here.

Both honeybees (above) and common eastern bumblebees (in this photo) “flock” to the Hyssop plants in great numbers.  But you notice that the while honeybee’s head fills the flower opening, the bumblebee’s head is too big, and it must rely on a long tongue to reach the nectar at the base.

Sometimes smaller is better, as far as pollination of the flower is concerned, because the smaller honeybee does a better job of contacting the flower’s reproductive parts and transferring pollen from one flower to the next.

Lobelia flowers were a perfect fit for the smaller worker bumblebees, but that didn’t keep larger-bodied bumblebees from trying to get its nectar.

Look what happens when this medium-sized bumblebee tries to get into the Lobelia flower.

This bumblebee is too big to fit into the flower opening, while another, smaller worker bumblebee, (below) crawls right in.  And notice how nicely that smaller bee contacts the protruding (white) stigma (the female reproductive part) of the flower as it enters and exits.  No doubt this bee will transfer pollen effectively.

This bee was able to work itself all the way into the flower, so that just the back legs were dangling outside.

Meanwhile, tiny little forget-me-not flowers, with their miniscule central opening, require the services of small bees with slender tongues to reach the chamber with the nectar.  Sweat bees are just the right size, and I found two different species hovering and probing the flowers.

That’s a pretty tiny opening to access this flower for its nectar supply.

Green sweat bees are common in the garden — I hadn’t noticed the black variety before today.  The green one looks well dusted with pollen.  Both species have sleek, almost hairless abdomens, unlike bumblebees and honeybees, but have lots of short hairs on their heads and abdomens, great places to collect pollen as they search flowers for nectar.

it’s all about the buzz

You’ve seen how busy bees gather pollen from some flowers — for example, they systematically crawl over the surface of Coneflowers and Black-eyed Susans, the tops of which are dotted with little ray flowers sticking their pollen up for grabs as the bee comes by.  Many different kinds of pollinators might walk around picking up pollen from these plants, so there is lots of competition for the pollen. But there is no guarantee that they will deposit any pollen on a nearby neighbor — they might just fly off to a completely different group of flowers instead.

A Common eastern bumblebee and a smaller green sweat bee competed for the pollen on some New England Aster flowers.

Other flowers present a nectar reward to the bee if it will kindly crawl into the tubular flower, brush against the anthers to receive pollen and then kindly deposit that pollen in another of the same type of flower they subsequently visit.  But who knows which flowers the bee might visit next — it might not be the same species at all.

A honeybee can crawl down the floral tube of the bee balm flowers to get at the nectar at the base, but the bee is not big enough to brush against the anthers (yellow-brown structures sticking out of the flower in the photo) to get a dusting of pollen.  Hummingbirds are a better fit for these flowers, and transfer the pollen from plant to plant very effectively.

Still other plants produce flowers that protect their pollen for just the right pollinator, one that specializes in picking up pollen from particular a species, and reliably deposits some of that pollen on a neighbor of the same species for some healthy cross fertilization.

Common eastern bumblebees are the chief pollinators of Spiderwort flowers in the spring.  The pollen in these flowers is encased (not free) in the anther, which opens from a pore at one end.

By locking the pollen up in a capsule, it is protected from just any random pollinator walking over the flower.  Shaking the flower might dislodge some of the pollen, but most pollinators can’t manage that.  Instead, bumblebees and some solitary bees grasp the anther capsule with their legs, or even mouthparts, and vibrate their wings at a very high (and audible) frequency — and pollen comes flowing out the pore at the end of the capsule, dusting the bee.  This technique is referred to as “buzz pollination”.

The video below illustrates the bumblebee action nicely:

“much of the food we eat owes its existence to the buzz of the bumblebee”

Scenes from the Cerrado – plants and their pollinators

Although we visited the Cerrado in the dry season, there were many shrubs and trees putting out new leaves and flowers, even in the absence of any trace of rainfall for the past 6 months.  Extensive underground aquifers that fill during the rainy season are tapped by deep roots of most of these plants, ensuring that they can flower and produce seeds when their pollinators and seed dispersers are present.

One of these small shrub/trees was quite common, and was particularly noticeable because of its huge displays of large, white flowers.

This is the Pequi tree, (Caryocar brasiliense), whose large white flowers produce copious nectar and pollen.  It blooms only during the dry season — July to September.

The leaves of Pequi trees are leathery, an adaptation to living in an arid environment. The flowers are rather large (bee in the top flower provides size comparison) and white with lots of yellow stamens.  They produce copious nectar throughout the night, which is higher in sugar concentration in the morning than the evening.

Artistic view of the Pequi flowerhead

If there were a single plant species whose absence would markedly affect insect, bird, mammal, even human populations in the Cerrado, the Pequi would be it.

Pollination is done mainly by bats at night, but the plant is also visited by nocturnal moths, wasps, and ants, all feeding on the nectar produced by the flowers.  In the daytime, no nectar is produced, but bees and wasps visit the flowers to feed on pollen.

Hummingbirds may be found on the flowers at dusk and in early morning, cashing in on that last sweetened formula of nectar the flowers put out.  Guira, White-lined, Palm, and Siaca Tanagers along with Curl-crested Jays also frequent the flowers at dusk as well:

Colorful Guira Tanagers sip the nectar, eat the flowers, and munch on the seeds of the Pequi.  Photo by Dario Sanches.

Curl-crested Jays hang around the Pequi trees in the very early morning hours, perhaps to feast on the insects that are attracted to the flowers. (Photo by Debbie Reynolds)

Glittering bellied Emerald hummingbirds are one of many hummingbird species that depend heavily on the nectar provided by flowering trees.

But that’s not the only role that Pequi plays in the Cerrado.  Well-pollinated flowers produce a bounty of nuts, eaten by animals and especially favored by indigenous people of the Cerrado.

Pequi seeds in Cuiaba, Brazil market (Photo by Mateus Hidalgo).

The pulp surrounding the seeds has been described as aromatic, fruity, and cheesy, and can be eaten raw or used to flavor other dishes.  The seeds (with spines removed) are roasted and eaten like peanuts, or crushed to extract their oil, so the whole fruit has great commercial value.  Pequi trees are typically planted around villages for residents to harvest the tree’s bounty.

Bees and blossoms

Spring is in full swing here in northern California, and I was glad to see so many honeybees out performing their pollinating service.  In fact, there were many more honeybees here than I typically see on the flowers in streetside gardens at home. Hmmmm…wonder what that means?

Honeybees swarmed the tinybflowers of California lilac (Ceanothus species)

They were probably collecting pollen from this plant (rather than nectar).  Look at those full pollen baskets on the rear appendages.

Twin flowers of this mint species offer nectar at the bottom of a deep floral tube, causing the bee to pick up pollen on its back as they brush by the anthers.

Better view of the plant-pollinator geometry that ensures the bee does its job for the flower while getting its reward. Bees typically spent several seconds on each flower, so either the nectar was hard to get to, or there was a lot of it (probably the former).

Bright purple modified leaves at the top of the flower stem attract bees to this fragrant mint. The tiny, purple-black flowers stud the sides of a thick floral stem.

I think this might be Spanish Lavender, which looks nothing like MN lavender.  It’s highly aromatic, like other lavenders, though.

California is experiencing a mega-bloom after all the recent winter rain, so I hope I will see a lot more of these plant-pollinator interactions in the next few days.

Macro moments

July is probably the highlight of color in my backyard garden, and what a feast for the eyes upon my return!  As I passed by the potted hibiscus that gets moved outdoors for the summer months, I noticed quite a few brilliant red flowers had just opened.

This is the tropical red hibiscus that is so popular as a house plant and a favorite of plant breeders hoping to create a new color variety.

Interestingly, red hibiscus is no longer found in its original native (Asia) habitat, but has been introduced all over the new world tropics where it typically grows into a tall shrubby hedge.  Hummingbirds and other nectar-lovers visit the flowers, but do they really pollinate it?  No one seems to know the answer.  It’s a very large flower, and the pollen-containing anthers are well separated from that 5-pronged stigmatic surface, so one would think something larger than a hummingbird must do the pollen transfer from flower to flower.

Such a beautifully constructed reproductive structure deserves a closer look.

The stamens (male) grow right out of the style that terminates in those 5 fuzzy-ball looking stigmatic surfaces (female).  You can see a few pollen grains sticking to the hairs below the stigmas.  One ball of pollen seems to be floating in air.

The anthers supported on slender pink-red filaments are full of yellow balls of pollen.  It doesn’t take much more than a shake of the flower to dislodge the pollen, but gravity causes it to fall down into the base of the flower, not out toward the stigma.

It looks like the stigma traps errant pollen grains with those long hairs on the ends of the style. The fuzzy surface of the stigma must make it difficult for pollen to make it down to the actual surface to germinate.

Red Hibiscus are apparently self-fertile, but the plants only resort to “autonomous self-fertilization” after a certain length of time, in order to permit pollen transfer from other plants to occur.  However, these flowers don’t last much more than a day in my garden, so pollinators would have to respond quickly to do the plant’s bidding.

What marvels we find when we look up close…

In search of pollinators

The plight of the honeybees got top billing in the Minneapolis paper today, with a feature article on our endangered food supply that is so dependent on bee pollinators, honeybees in particular.

Bees of all sorts love the nectar of the late summer blooming sedums. I rarely see such a concentration of honeybees on a plant these days.

You might have known about the California almond crop dependency on honeybee pollinators (in fact, almonds are 100% bee pollinated), but broccoli, various fruits including cherries and blueberries, cucumbers, and melons (among 100+ foods we eat regularly) are also heavily dependent on bees for pollination and fruit set.  Honeybees are in trouble for a variety of reasons, many of which have to do with the impact of agro-chemicals on insects of all sorts.

Butterflies are less important for pollination of agricultural crops, but vital to the pollination of certain wildflower species. Butterfly weed (Asclepias tuberosa) probably got its name originally as a result of its attractiveness to a variety of butterflies (as well as bees).  But where are all the butterflies these days?

Their bright orange advertisement should bring pollinators running (or flying) to it, but ants were the only insects on this plant sitting in the middle of a 10 acre prairie.

Ruby-throated Hummingbirds enjoy the nectar that butterfly weed flowers have to offer, but they don’t move pollen from plant to plant. I never saw butterflies, and rarely any bees, on this plant in my garden, but they did manage to make a few seed pods.

Our local butterfly populations seem sparse compared to what they were a few years ago, whether a result of harsh winters, late springs, drought in areas through which they migrate, habitat destruction in their overwintering areas, or too many chemicals in the environment.

In a 3 hour walk around Tamarack nature center this morning, I saw this one Swallowtail butterfly (nectaring on Hoary Alyssum), one Red Admiral, and one Wood Satyr. Three butterflies in three hours — not a very impressive count.

In China, they pollinate fruit crops by hand — I hope that isn’t what we will have to resort to in the future.

It’s a hummingbird! (moth)

Hiking around on an oak-savanna property recently acquired by the Nature Conservancy out in the Glacial Lakes area, our group spotted what they thought was a hummingbird hovering over flowers of the Bladder Campion.

It hovered just like a hummingbird, but it’s not a bird. It’s a hummingbird moth, AKA the White-lined Sphinx Moth.  It’s difficult to see the striking white lines on its wings in this photo, but the white lined pattern on its thorax is also distinctive.

It is rather large, for a moth, with a wingspan of 3-4 inches.  Like a hummingbird, the moth flitted from flower to flower, pausing only briefly to insert its extremely long proboscis to test for the presence of nectar before moving on.  A very difficult subject to photograph!

A closer view reveals that this moth has a proboscis that is even longer than its body length.  Adults seek nectar from a variety of sources including columbines, larkspurs, petunia, honeysuckle, lilac, clovers, thistles, and Jimson weed.  And they are not particularly fussy about where they live —  in open habitats in deserts, horticultural gardens, or even suburban homes.

Later, while walking around a different prairie a few miles away, one of the group discovered a very large green caterpillar munching on a fragile wildflower.

The caterpillar was about 3-4 inches long and almost 1/2 inch in diameter, probably almost big enough to pupate. The orange horn sticks up on its rear end; the head is tucked in and hidden.

This is most likely the caterpillar of a White-lined Sphinx Moth; they can be highly variable in color but the orange horn is a key feature of this species.

It takes about 8 weeks to grow into a caterpillar this large from an egg.  Most likely this one overwintered as a caterpillar to complete its development this spring. Once the caterpillars reach a critical size, they pupate underground and emerge as adults in 2-3 weeks.  Mated females then begin the cycle all over again, laying up to 1000 eggs on a variety of host plants (e.g, four o’clocks, purslane, fuschia, evening primrose, elm, grape, and tomato) while sustaining themselves on flower nectar.

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.  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.  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.

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 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 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.

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

The End.