Solstice and More

a satisfying flower show

A trip to Cowee Meadows is always worth dealing with some broken or missing boards and a few flooded (sometimes ankle deep) sections of trail—a common occurrence after rains. Around the time of the summer solstice, the wild iris take over, with shades from pale lavender to deep, rich purple covering much of the meadow but leaving some room for buttercups, lupines, and the last shooting stars.

On the slightly higher ground, some stands of the wild rose were just starting to flower while others were almost finished. The big white inflorescences of cow parsnip made a good framework on the meadow edges. They were often occupied by dozens of tiny, slender flies, presumably sipping up nectar from the little flowers that comprised each inflorescence. Fireweed had yet to come, but the buds were promising.

A common flower, dotted in among all the others, is the chocolate lily or rice-root. The typical brownish flower smells fetid (unlike most flowers) and is pollinated by flies. The shades of brown vary: some are very dark, even reddish, some are mottled with green or yellow, and a very few are mostly yellow. Do the pollinators care?

Photo by Kerry Howard

The sprawling shore plant called oysterleaf is widespread in northern latitudes. Its flowers are normally blue, but rarely white, according to two field guides, but we found white-flowered individuals to be quite common. The flower is insect-pollinated in some regions but is said to self-pollinate in others.

Few bees were flying on this day, but they are probably the principal pollinators of iris (as well as visiting many other flowers). A small insect might enter the flower but would not be big enough to contact the sexual parts. A bee crawls into the iris flower over a drooping petal-like sepal (the true petals are smaller and upright), passing under a narrow arm that bears the stigmatic surface where pollen is received, and then under a rod-shaped, pollen-producing stamen on its way to the nectar deep inside the flower. Cross-pollination would happen if the bee visited more than one flower, but the flowers are reported to be self-compatible, so if a bee happens to pick up some pollen on its way out of the flower and deposit some on the stigmatic surface, a seed might be produced that way.

Photo by Bob Armstrong

An aquatic plant long known as Potentilla palustris (marsh cinquefoil) was always a bit of a puzzle to me, because most potentillas have yellow flowers and five petals but this one seemed so different, with its red- or purplish-flowers with six or seven petals. I’ve just learned that botanists have now recognized these and other differences by assigning this species to a different genus; it’s now Comarum palustre. The flowers are reported to have valuable pollen with lots of essential amino acids and lots of concentrated nectar, and they are visited by many kinds of insects.

In the muskeg at the start of the trail, we inspected the bog laurel flowers. When an insect (not too small) visits the flower and walks around on the petals of the open flower, the stamens usually spring up from their niches on the surface of the petals, potentially placing pollen on the insect. So we could tell which flowers had been visited. A visiting insect might also bring in some pollen from another flower, effecting pollination. Our inspection revealed that some aging flowers had no sprung stamens and presumably would not set fruit, but some fresher flowers had clearly been visited and might set fruit.

On the way through the woods down to the big meadow, the dainty little wintergreen called single delight or shy maiden presents its one little white flower to insect visitors, typically a bumblebee. A visiting bee rapidly shakes the anthers, which releases pollen for the bee to eat and collect. The flower is demurely held face-down as it awaits a bee, but if pollination occurs, the flower raises its head–no longer shy– as the fruit matures. We joke that it is now a brazen hussy. Here’s a link to that process.

All told, we found over sixty kinds of flowers, but we didn’t beat our record from a previous year of over seventy-five species. Still, not bad!


Cowee Meadows

a May expedition finds flowers and toadlets

Photo by Deana Barajas

Several things combined, recently, to bring me a strong wave of nostalgia for the Midwest. I love the oak trees—their varied forms and leaf shapes and acorns. On top of that, my brother in Wisconsin regales me with tales and pictures of the birds that throng his feeders—orioles, goldfinches, rose-breasted grosbeaks, catbirds, and more—species that I’ve not seen for a long time. Then one of my old post-docs, in Chicago, wrote to me about all the spring flowers that grace the woodland floors—Dutchman’s breeches, bloodroot, spring beauty… Aaahh, I do miss all that!

However, on the last weekend in May, a bunch of regular Saturday hikers went out to Cowee Meadows. On the way down the trail, we enjoyed the many bog laurels and bog rosemary flowers in the muskeg, and we stopped to inspect the young bracken ferns for nectaries. Cowee Meadows is a place I like to visit several times as spring becomes summer, to see the seasonal development of the flower show. A couple of weeks ago, there were a few shooting stars, some buttercups and marsh marigolds, but little else. But now, the meadows were awash in color: lots of yellow buttercups, shooting stars in all shades of pink, joined now by tall blue lupines. Hidden under the taller plants were violets, starflowers, and the coming chocolate lilies. Even without the famous irises and the banks of roses, which will bloom in a week or two, this is a spectacular sight—hard to beat! Carpets of strawberry flowers out near the river weren’t bad, either, even though I never get there in time to harvest any of the fruits. Nostalgic feelings were successfully subdued.

Photo by Louise Ketcheson

One of the most common plants in these meadows is the shrub called sweetgale (Myrica gale). It is very aromatic, and the nodules on the roots fix atmospheric nitrogen into a form usable by vegetation. The books say that sweetgale is typically dioecious—male and female on separate shrubs, but occasionally hermaphroditic—both sexes on one plant. Yet the shrubs all looked the same to me; where is the other sex? Then I read that, for unknown reasons, sweetgale males commonly outnumber the females by a big margin. So the many shrubs we see bearing small cone-like structures are presumably males. But if so, what do the females look like? Two field guides and a few official floras were no help at all; if they illustrated any flowering parts, it was the typical cones, and the verbal descriptions were unhelpful. Finally I discovered a website (thank you, Minnesota) that illustrated both male and female inflorescences.

It turns out that the rare female inflorescences look like small, red tufts along a twig. Knowing a characteristic that is useful in the field, we have now found two stands of female sweetgale shrubs and a few mixed-sex individuals in a population that is overwhelmingly male. Good to have that sorted out!

Another satisfying observation on this hike was seeing tiny toadlets making their way through thick tangles of herbage. I don’t know in which pond or slough they spent their time as tadpoles, but with patience, they can travel quite a distance once they have legs. One of these toadlets was crawling about on the upper beach, which is hardly a suitable place for a growing toad. Although it is tempting to catch them, we must remember that if we have insect repellent on our hands, it can poison them through their skin. And, in any case, it is illegal to hold, transport, and release them. Better to just observe and protect them!

When I got home, there was fun at my bird feeders. When the pushy jay and the big hairy woodpecker aren’t there, chickadees, nuthatches, and juncos use the peanut butter feeders daily. I started watching more closely as the three smaller birds pecked at the peanut butter lumps on the feeder. Peck and gobble, peck-peck and gobble. But the last peck gets a little gobbet that doesn’t disappear into the inside of the bill. A small wad of peanut butter is carried off into the woods, and I’m betting that it goes to a chick.

Insect vision

and what they see in flowers

Most adult insects have two kinds of eyes. Small “ocelli” on various parts of the head are light-sensitive but are thought not to make good images. The two large “compound eyes” that are used for finding food or mates or landing sites are actually composed of numerous single light receptors called ommatidia. There are thousands of ommatidia in the compound eyes of some insects, such as dragonflies, but only a few in ants. In day-active insects, each ommatidium typically forms its own image, so what a compound eye sees is a mosaic. A mosaic isn’t as clear as the single image made by a vertebrate eye, but compound eyes are very good at detecting motion.

Day-active insects typically have good color vision, although they have little sensitivity to red. Most of these insects have two peaks of light sensitivity, one in the green-yellow range of wavelengths, the other in blue and ultraviolet (UV). But honeybees, bumblebees, and most butterflies generally have three peaks of light sensitivity: for yellow, blue-violet, and UV.

Many of us are familiar with hummingbirds’ preferences for red. Insect pollinators also have color preferences —bees for blue, hoverflies for yellow. But they are certainly not restricted to those colors and may visit many kinds of flowers, using color as one means of telling them apart, so they can learn to avoid those offering little reward.

Showy flowers with pretty petals and other ornamentation evolved to attract pollinators; they are part of a sexual display, making use of insect color-vision in achieving pollination. The wide array of colors and color patterns of flowers (along with size and shape) helps insects to discriminate among flower species and concentrate their visits on those that offer the best access to food rewards (exceptions include flowers that are false advertisers, as discussed in a previous essay). From the flowering plant’s point of view, concentrating an insect’s visits increases the probability that pollen is transferred among plants of its own species and less is wasted on some other kind of flower, with no reproduction accomplished.

Humans can’t see UV, so flowers look quite different to us than to a bee or butterfly. Some flowers have particular UV markings (which we can ‘see’ only with special equipment) that help identify the flower or perhaps guide an insect visitor to the right place and position to obtain nectar and effect pollination. Here are some local examples:

Silverweed (Potentilla anserina) is common on our wetlands, yellow marsh marigold (Caltha palustris) grows in some sloughs and slow creeks, and large-leaved avens (Geum macrophyllum) grows along many trails. All three have flowers that are yellow to human eyes. And all three are reported to have flower centers that absorb UV and look dark, in contrast to the outer parts of the petals, which reflect UV and are bright. Many bee-pollinated yellow flowers are said to have this arrangement, with UV absorbing centers and UV-reflecting peripheries.

The blue harebell (Campanula rotundifolia) reflects UV on the female sexual parts (pistil and stigma). Field chickweed (Cerastium arvense) has white flowers that reflect UV strongly. The yellow monkey-flower (Mimulus guttatus) has two different life-histories: some are perennial and some are annual, and the UV markings on their flowers differ too. Bees are reported to discriminate against whichever pattern is unfamiliar to them.

Long-leaf sundew (Drosera longifolia) that grows in some of our muskegs has white flowers. But the petals and sexual parts absorb UV while the nectaries are strongly reflective of UV rays. Interestingly, in this insectivorous plant, which traps bugs on its leaves, the leaf blade absorbs UV but the sticky drops on the bug-catching tentacles have strong UV reflectance, making a big contrast.

Among the orchids, the forest-dwelling species known (for some strange reason) as rattlesnake plantain (Goodyera oblongifolia) has white flowers and is bee-pollinated. But the forward-projecting, cup-shaped middle petal (called the lip) is reported to reflect UV as a bright yellow-green. Yellow ladyslippers (Cypripedium parviflorum) are said to have very UV-reflective tissue around the opening of the lip (or “slipper”), at least in some populations. UV patterns of calypso orchids in Southeast are now being investigated. (Thanks to Marlin Bowles for digging up the information on orchids.)

Some of our non-native flowers have UV patterns too. Dandelions absorb UV in the center and reflect UV on the outer fringe of petals. The little weed called herb robert (Geranium robertianum) has a dark-centered, UV-absorbing pink flower. Orange hawkweed (Hieracium aurantiacum) has orange-red flowers that are said to reflect a checkered pattern.

Many other local species have apparently not been examined for UV-absorbing and -reflecting patterns. There’s a photography project waiting for someone!

Exactly how the UV patterns work in attracting insects or in focusing an insect visitor’s attention on the nectar source and sexual parts of the flower is not well documented, it seems. Insects may sometimes be indifferent to them or attentive only in certain conditions. More research is needed.

Fun at Home

looking out the windows

I love to walk our trails, just to see what I can see. But sometimes there’s a lot to see in my front yard and pond. Then I wear a path from window to window (with side trips to the fridge and tea kettle). This spring has provided some home-based fun.

The shenanigans of the mallards are an annual happening. The ducks start to visit the pond soon after ice-out. Pairs sort themselves out and by late May mama ducks start to bring their tiny ducklings for an occasional visit. This year there were several brood of eight or nine and one brood of just one duckling.

The littlest ones have a hard time jumping up to join mama on the bank for a rest. They zip back and forth in front of her and make lots of futile little leaps. The female often tries several spots before finding one they can all master. Sometimes only part of a brood makes the jump and the rest have to find access at some distance and make a small overland trek. When ducklings are small, the mother broods them, making herself as broad as possible to cover them all, although even then a few heads and tails poke out from under her.

The unpaired males that have already fathered these broods are hanging about, all revved up and looking for more action. They harass any late-forming pairs and even mothers with babies, causing lots of fuss and flapping. The female with one offspring was persistently pursued, driving her to protest continually and even leave the pond several times. If I opened the windows, I could hear the little one peeping in apparent distress.

A flotilla of visiting ducklings is probably what brought an eagle down to march along the bank, eyeing one brood with malevolent intent. (Yes, I know, eagles have to eat too.) A swoop or two over the water failed, as the brood scooted for cover, and the eagle left, still hungry.

Juvenile juncos had been chip-chipping in the woods along various trails since mid-May. Here at home, there were well-fledged juveniles, of two separate families, by the first week of June, quite able to pick up seeds for themselves but often waiting for dad to deliver. It was the male juncos that stuffed the juveniles with peanut butter and seeds, leading me to suspect that the females were back on eggs again, for second broods. (They can do three or four a year.) The juveniles tried the peanut butter feeder occasionally but looked like they needed some practice, and they preferred to wait for dad.

A male hairy woodpecker made occasional visits to peanut butter and suet, but by mid-June his visits were quite frequent. He hacked out big chunks of suet and carried them off, leaving crumbs for the little birds to pick up. He would swallow several bits of peanut butter but carry away one last load in his bill. So I knew he had a family. And finally, a big, well-feathered fledgling joined his father on the deck railing and begged for peanut butter. I wondered if the mother was tending another young one somewhere.

The chickadees were feeding big kids too. And a great treat was seeing the whole family of nuthatches crowding together on a small block of suet. Two sleek fledglings chipped off bits of suet for themselves, but were also happy to have chunks delivered by the parents.

A bear came to eat horsetail in my front yard. They do this every year. Often they lie down flat and just scoop in the green stuff. This guy got up and wandered up toward the house, sniffing and sniffing, then stood under the edge of the deck to sniff some more. No doubt the aroma of peanut butter was in the air. Before I could say oh-oh, the bear shot up a nearby tree like lightning, just a black blur. It went up above the roof level, out of sight. Now, I’m not too enthusiastic about a bear on my roof (or deck). I raced outside to check the roof, but by then it was already down and gone. The tree was just a bit too far away from roof and deck. But just in case, I have moved the alluring feeder to the other end of the deck; the birds are getting used to the new arrangement.

One more bear story: A medium-size cinnamon bear came and foraged on horsetail. That gave me time to see that she looked like she’d worn a collar for a long time because her fur was very worn in a circle around the neck, but she had no visible ear tags. Eventually, she started to wander out of sight. Immediately, an alder tree across the pond gave a violent shudder, and a massive glossy-black bear suddenly appeared in the yard. He chomped a couple of horsetails but was much more interested in her, and he followed her off into the neighbors’ yard. It’s that time of year for bears!

Long Distance Migrations

by individuals, and across generations

Many animals make regular seasonal migrations. Some are quite short: I’m remembering the snakes that hibernated in deep crevices in Midwestern bluffs and came down to nearby swamps and floodplains for the summer, going back to the bluffs for the winter.

At the other end of the spectrum are some extremely long migration distances (note that the following distance estimates take little or no account of detours to follow shorelines or concentrations of prey, etc.). The Arctic tern is generally considered to be the champion, migrating from Arctic to Antarctic and back every year, an annual round-trip distance of perhaps as much as 25,000 miles.

But other species are also impressive: the bar-tailed godwit flies nonstop (!) from Alaska to winter in New Zealand, a distance of almost 8000 miles in eight days; on the way back, they take a longer route and stop over to fatten up in the Yellow Sea (between China and Korea) –in total, a round trip of over 18,000 miles. Aleutian terns go from Alaska to Indonesia and south-east Asia for the winter, covering perhaps 20,000 miles each year. The little shorebirds called sanderlings breed in the High Arctic; some of them fly to Tierra del Fuego for the winter, and back again in spring, a round-trip of close to 20,000 miles.

Some seabirds that nest in the southern oceans go north for their winter. Sooty shearwaters fly from their nesting areas in the Falklands and Tierra del Fuego to Arctic waters near Norway and back again, over 17,000 miles in the Atlantic (round trip); in the Pacific, they fly even farther, from near New Zealand to the Gulf of Alaska. Short-tailed shearwaters fly even farther: they breed near Tasmania and migrate to the North Pacific; some even go through the Bering Strait to the Arctic Ocean.

All of these critters are relatively long-lived, with lifespans measured in years or decades, and may make those journeys many times in their lifetime. And in most cases, they can feed along the way.

There are long-distance migrants among the insects too, but they are relatively short-lived, with lifespans (for active adults) measured in days or weeks, and they do it differently. A single individual does not make the round-trip journey; instead, they breed along the way and the next generations take over the route.

The best-known example in North America is the monarch butterfly. Monarchs that are born and raised in the eastern U.S. and southern Canada migrate to special forests in northern Mexico for the winter (occasionally some go to Florida or other places in southeastern U.S.). When spring comes, they start north again, but they stop to breed along the way. It takes two or three weeks for each generation of eggs and caterpillars to mature into the migrating adults. That new generation continues northward, and again they stop to breed. It may take three or four generations for monarchs to reach their northern-most range, where they produce the long-distance travelers to Mexico. There is also a smaller population of monarchs west of the Rockies; it migrates to California and northwestern Mexico. But monarchs are in deep trouble, due to habitat changes that reduced the availability of milkweed plants on which the larvae feed and to serious deforestation in their particular overwintering sites in Mexico.

Painted lady butterflies do something similar. From wintering areas in Mexico they migrate northward in multiple generations to the Canadian border; the European populations migrate from south of the Sahara Desert in Africa to northern Europe and even Iceland, making several breeding stops on the way. Red admiral butterflies winter in southern U. S. or southern Europe and commonly migrate north in spring, but shorter distances than the painted ladies.

Painted Lady. Photo by Bob Armstrong

Perhaps surprisingly, some dragonflies are good migrants too. In North America, the big, beautiful green darner had a complicated arrangement, with a roundtrip distance of nine hundred miles or so. It migrates from wintering areas in southeastern U. S., the Caribbean, and Mexico as far as southeastern Canada. One generation makes this great leap and breeds. Some of the resulting offspring stay there, overwintering as larvae in ponds. Others migrate south to the wintering areas, where they reproduce, and these adults are residents in the wintering area, but their offspring will be the next year’s northward migrants.

An even more far-traveling dragonfly is called the globe skimmer. It is widely distributed on many continents and apparently moves around a lot; they have been recorded flying over the Himalayas. But even better: some of them fly over the Indian Ocean from India to East Africa. Some of this over-four-thousand mile flight seems to be nonstop, although the dragonflies might stop to breed if they happen to find an island with suitable conditions. After breeding in Africa, they go back.

That’s not the end of amazing insect migrations. Two kinds of hoverflies, less than a centimeter long, migrate from the European continent to Britain. There they pollinate many kinds of flowers and their larvae gobble up aphids. There may be several generations in a summer. Then the last of the summer-produced generation flies back to the mainland. From there, one species heads to North Africa to spend the winter and make a new northbound generation.

There is surely a lot more to be learned about insect migrations! For instance, how do they navigate? There are likely to be more of such interesting migrations, yet to be discovered.