Of Crane Flies and Newton's First Law of Motion

Mating Crane Flies

My friend, Jim, knows that I like to work late and sleep in. So he emailed this morning to tell me about the mass of at least 50 crane flies in a mating frenzy behind his garage. Jim's a fisherman so he knows his flies, and he also knows my interest in anything bug-related. But by the time I arrived on scene we could only find three flies, one coupled pair and one exhausted male. They looked to be the back-spotted crane fly (Tipula dorsimacula).

The coolest thing about crane flies isn't that they look like huge mosquitoes. They're just harmless flies that don't bite, and most adults don't even eat. Nor is it that the adults only live for 10 to 15 days. They sometimes form breeding leks (like Jim found) for a brief mating frenzy, soon followed by egg-laying and death. (In this photo, the precocious female at top has just emerged from the leaf litter larval stage, and her new wings haven't even expanded fully!)

The coolest thing isn't even the fact that you can tell a crane fly's sex just by watching how it flies. Males fly with a bouncing up-and-down motion while females fly more straight-line. No, these flies have something special that any science geek would love.

The coolest thing about crane flies is a special pair of club-like appendages, called "halteres," that work in conjunction with Newton's first law of motion to assist in their flying skills. (Remember that one? It says that an object in motion remains in motion unless acted upon by some force.) Although, it is puzzling that in spite of their scientifically-aided flight, crane flies are probably the slowest and clumsiest of all fly species (excluding flightless flies, of course).


Close-up showing a crane fly's left haltere, the club-like appendage below the wing and above rear leg

In ancient Greece, halteres were a special pair of hand-held weights that athletes swung back and forth to help them leap ("fly") farther in long-jump competitions. In some modern-day fly species, halteres are paired appendages that flap rapidly up and down with the wings, functioning as tiny gyroscopes.

Dorsal view of paired halteres

Obeying Newton's first law, each flapping haltere maintains its plane of vibration until the crane fly changes direction. When the fly turns even a tiny bit, the halteres exert pressure on the fly's body that is detected by sensory organs (called campaniform sensilla) that are located at the base of each haltere. In this way the halteres provide rapid feedback to the flight muscles, help stabilize the head, and effectively steer the body in flight. Or, at least more effective flight than without halteres.

But wait, there's more. It turns out that the formation of halteres in flies is controlled by a single gene. When this gene was experimentally turned off in the science lab, during metamorphosis from larva to adult, a pair of fully functional wings formed instead of halteres. Holy batman!

Amazing features that you learn about crane flies might not morph you into a fly fan, unless you were previously susceptible to curiosity about bugs. But still, you've gotta' admit that flying gyroscopes that could be wings instead are pretty darned cool. And in this particular case, pretty funny as well.

The funny part? My friend, Jim, has an elderly uncle who is very creative. Uncle wants to patent a hat that he invented for elderly people to wear. It features a pair of gyroscopes that, according to uncle, helps older folks walk more effectively and prevent accidental falls. Maybe he should name his invention the "Haltere Hat."

Down to the River

Arctic Grayling spawning in northwestern Montana

After a couple of weeks of running non-stop, I finally got a chance to sit still today. I chose to plop down in the mud beside a little creek here at the end of the road. During much of May, this meter-wide creek gurgles and splashes with thousands of spawning fish, Arctic grayling (Thymallus arcticus). After running up the creek for a few weeks, many of the fish have returned to the lake and we're down to "just" a few hundred remaining in the creek nowadays.

These grayling are native to Montana but not to this little stream, or the lake that it flows into. How they arrived here almost 90 years ago is an interesting story, but one I'll save for another day.

Today I just wanted to sit and watch fish. I carried my little underwater video camera along because, well, I can't help myself. The evening was dark and spitting rain - not really enough light for filming. But I stuck it in front of some fish anyway, shooting some grainy and underexposed footage. Sometimes it's better to just sit in the mud and watch.

Little Promises of Summer

Huckleberry flowers blooming today near Whitefish

Don't look now, but there are hordes of young huckleberries growing up wild in the woods. Better yet, get out and look closely at the spring huckleberry flowers that are just now starting to bloom, then come back later in summer for taste-testing.


An androecium of yellow stamen hidden inside

From above, huckleberry flowers can look surprisingly like reddish berries that are two months early. The bell-shaped flower has a small opening that invariably opens downward - which probably relates somehow to successful pollination during May and June, our rainy season. By gently twisting the stem, you can peer inside the tiny flower to see the working parts.

The yellow, pollen-forming stamen are hidden in there, tucked away and dry on the inside. (The whorl of stamen is called an androecium, Greek for "man house.") The pollen-catching stigma sticks out just far enough to be a minor obstacle to any insect trying to crawl inside. (The stigma is visible below the greenish flower, in the upper photo.) Previous visits to other huckleberry flowers might have left a little pollen stuck to the insect, and now this pollen rubs off onto the stigma.

Presto! Some of the seeds are fertilized, a berry begins growing, and summer starts taking shape in northwestern Montana.

Snow Lilies for Mothers' Day

Glacier Lilies blooming this week in Glacier National Park

"Near our encampment we saw great numbers of the Yellow lilly with reflected petals in blume; this plant was just as foward here at this time as it was in the plains on the 10th of May."

                                 - Captian William Clark 

A modest 207 years ago today, Captian Clark collected his first specimin of a native plant with a handsome yellow flower that was previously unknown to American and European botanists, though the plant was a well-known food and medicine for a number of northwestern Native American tribes. Clark wrote about these lilies in his journal entry from June 27, 1806. The species he collected has since been called Dogtooth Violet, Snow Lily and Fawn Lily, but it currently goes by the moniker of "Glacier Lily" (Erythronium grandiflorum Pursh).


Trillium in bloom

The Expedition was travelling through the mountains of Idaho, and they frequently commented about how much snow remained "undissolved" in May and June. Captian Clark took note that the Glacier Lilies growing at high elevations were almost two months behind their counterparts growing lower down on the plains. And that is still happening in the springtime mountains of northwestern Montana.

In localized patches in and around the melting mountain snowfields, Glacier Lilies and the slow-growing but long-lived Trillium (Trillium ovatum) are putting on a modest show of persistence, just in time for Mother's Day. Need another reason to get outside this weekend?

The Final Journey

A trail of deer hair leading through the woods

So five of us were slogging out of a cedar forest on this wet and windy afternoon, worn down and weary after three hard days of fieldwork in this Glacier Park drainage. That's when we stumbled across a trail of white leading over the reddish-brown forest floor. Deer hair, and quite a bit of it. Individual deer hairs are brown on the outer tips, fading towards grayish-white near the skin.

This trail of fur mapped one deer's final journey through the woods. A good-sized deer either died or was killed, and then its carcass was drug backwards through the forest duff, over fallen logs, through sapling thickets and across ice patches. I suspect that it was drug hind end first, against the grain, based on how much hair was left behind.

Ask any hunter, a dead deer isn't an easy thing to drag around - unless you're a big and strong something-or-other. Our weary group of biologists/naturalists couldn't decide if this was the handiwork of a bear or a cougar, and we were too tired to follow the path of hair to see where it led (as any good naturalist would do). Instead we turned and continued our trek, and one-by-one we each patted the comforting shape on our belts to confirm that our cans of bear spray were handy.

Spring in Fits and Starts

Spring arrives to these woods in fits and starts. But at least mud season is finally winding down here at the end of the road. Our days are above freezing for the most part, but nights are still cold enough to firm up the mud bog between here and pavement, some miles away. If we want to go to town, we go early. But really, who wants to go to town?

In this part of northwestern Montana, the high and low temperatures on April 15th averaged 56F and 31F over the past eight years. We'll still see snow flurries into May, maybe even June. But the ice and snow linger less as the nighttime temps crawl upwards. Still, as long as it freezes overnight, we get to watch for interesting weather creations.

Spent high noon today down by the creek. A little snow lingers in the deeper shadows, but not along the stream banks where snow melt has steadily raised the water level over the last week. Soon, grayling and trout will wriggle up into this current. But today's curiosities were splash-cicles, ice creations wherever the water gets rowdy enough for a splash zone.

Where dried grass stems bend down towards the gurgling water, one yellowed twig danced back and forth. Where it ended, water droplets washed across an ephemeral ice globe dangling just above the surface. Plum-size today, but I'll check to see if it's still around tomorrow. Nearby, a bright red dogwood stem dipped into the churning bubbles, weighed down by a half-inch coating of clear ice - denser and heavier than winter rime.  In a few weeks time, fragile green leaves will replace these icicles. Only then will we say we made it through another Montana winter.

Northern Pintails: From Punk to Hunk to Studly Duck

In the animal world, competition for a mate is a struggle with a thousand different strategies. Let's follow the twisting path taken by just one species. Male Northern Pintails (Anus acuta) start courtship as young punks who must grow into handsome hunks before they even have a chance to change into studly ducks. But only the chosen ones will make the final, hormonal transformation.


Northern Pintail courtship flock, six determined males following one female (upper right)


In much of the bird world, it's the female who picks her mate from among the mass of males who strut, sing and/or otherwise trying to get her attention (while simultaneously knocking down rival males). We call this, "female choice," and it's a big part of what drives the evolution of many male bird traits, from gaudy feathers to complex song repertoires.

Even slight genetic variations can potentially lead to exaggerated traits. Females who choose a mate for, say, a slightly longer tail feather, will tend to produce daughters with the same (genetically-driven) taste in tail feathers, and sons who tend to inherit the longer-tail-feather genes from their father. Run this through enough generations and you get, for example, the peahen and the peacock. The plain brown chicken and long-plumed rooster.

Over the past month, tens of thousands of Pintails migrated through Montana on their way to dispersed nesting sites. Early in the migration we often saw small courtship flocks that consisted of one female followed by a cohort of males. Some of the males were doggedly determined to stay as close as possible to the lone female, while other males would soon give up. Whenever she took to flight, the group turned into an amazing aerial ballet of high-speed, precision maneuvers that would leave our own Blue Angel studs dizzy.

As these male Pintails aged and began courting females, there have been a number of invisible, chemical changes taking place in the bloodstream. Careful hormonal and behavioral research has partially teased apart these chemical maneuvers.

When one- and two-year-old male Pintails were experimentally grouped together, some were more aggressive and some were less aggressive, and they established a dominance ranking or "pecking order" that was unrelated to age. Also, the before and after levels of four plasma hormones (testosterone, dihydrotestosterone, luteinizing hormone and corticosterone) were unchanged by the male-male competition for rank.

And when female Pintails were placed together with different males, one at a time so that male's dominance rank was eliminated as a factor, the females showed a significant preference for males with pure-white breast feathers and colorful scapular (shoulder area) feathers. They paired only with the more handsome males, the "hunks." So the males' dominance rankings were unrelated to their pairing success.

But when a female Pintail was placed in with a group of males, things got real interesting. Male behavior returned as a factor in pairing success. Compared to the younger "punks," the two-year-old males tended to be more attentive to the female, and courted them much more aggressively. The females chose a mate from among these attentive males. From this sub-group, the females again chose the male with the brightest and most colorful feathers.


Aggressive paired male (center) picks a fight

Surprisingly, the winning hunk wasn't always the highest ranking member of the all-male group. However, after a male was chosen by a female, he quickly became more aggressive and initiated fights with the more-dominant males. And the newly-paired male soon fought his way to the top of the pecking order.

Why? Because getting chosen by a female changed the male's blood chemistry, his hormones, in a surprising way. Chosen males saw a decrease in testosterone and an increase in corticosterone. Increasing corticosterone levels meant that the male could quickly mobilize the energy he had stored as fat, which increased his energy levels and helped him drive away other males. The male suitors who were not chosen by the female did not experience a significant change in hormone levels.

Again, there was no correlation between a male's pre-pairing dominance rank and his age, or between his pre-pairing dominance rank and his pairing success. Male dominance behaviors did not constrain female choice. Overall, mate selection was driven by a sequence of different strategies.

First, the male had to be old enough to aggressively court females. This age- and hormone-induced behavior moved him into the second round. Then he had to be healthy enough to produce handsome feathers. This was the genetic evidence that the female actually based her decision on. And finally, after being chosen by a female, male hormones shifted in a way that raised his rank among males so that he could more easily protect her from unpaired males.

In Northern Pintails, it's not a straight line between courtship and pairing. Finding a mate is seldom a simple matter, and it gets even more complex when you start looking beneath the colorful feathers.


Female Northern Pintail (right) following her studly mate

Behind the hormones: The dip in testosterone seems counter-intuitive and still has me a bit puzzled, but none of the studies I've read addressed it, so that one's still a delightful mystery to me.

Of course, adult human males are not immune to the effects of females, either...

Iris Has Returned to Missoula!

Okay it's been a week now, and this time the nest watchers are sure - Iris has survived the winter and returned to her nest. Iris is a wild Osprey who returns each spring to the Clark Fork River in Missoula to raise her family. It's a modern nest, all things considered, that includes a high-tech streaming web cam so you can watch her family grow - at least during daylight.

Iris arrived on April 2nd this year, but another bird spent some time on Iris' nest earlier in the week, so that fooled everyone at first. Now the nest watchers believe that the first Osprey was a youngster who was prospecting for a new home. That bird didn't behave like a homeowner, and didn't deliver any new sticks to spruce up the nest. Iris, on the other hand, has been busy bringing in new material and rearranging things just so.

Iris arrived in Missoula about the same time last year. Her mate showed up a few days later but was only seen for one day before he disappeared. Iris spent three weeks alone before a new male arrived and paired up with her. Her new beau (playing the role of Robert DeNero) was soon dubbed, "Stanley." Iris and Stanley raised three youngsters in their nest in 2012.


Osprey migration map from western Montana,
Sept. 1st to Oct. 13th, 2012.

Now that she is home again, Iris - and the rest of us - are watching and waiting to see if Stanley also survived the winter.


Behind the webcam: Iris' camera is part of an on-going effort to monitor about 200 Osprey nests in western Montana, by the Raptor View Research Institute. At their website you can learn much more about our local Osprey, including more nest cams, Osprey migration maps from 2012, and even a female Golden Eagle named, "Elaine," who was wearing a satellite transmitter when she left Montana in 2010  and headed for Alaska!
 
BONUS: you can also check out the Missoula Great Horned Owl and  Long-eared Owl webcams.

Tree Swallows Have Arrived

Tree Swallow (Tachycineta bicolor) observed yesterday in northwestern Montana

Tree Swallows (Tachycineta bicolor) have returned to western Montana, about a week earlier than average. Of the nine North American swallow species, this one winters further north and returns to its breeding grounds earlier than the rest.

Tree Swallows nest all across Montana, faithfully returning each spring to their previous breeding sites. One study found that 96% of adult males and 86% of adult females returned to the previous year's nest. These swallows like to nest near open water, where they forage for flying insects. But these early-returning birds won't start egg laying until the flying insect populations reach a certain density, ensuring enough food for their hungry hatchlings. Insect populations are in turn related to average air temperatures and, as our climate warms, Tree Swallows have moved their mean date of nest-initiation forward by 10 days over the past 30 years.

Researchers also found a correlation between the timing of egg laying and mean wing beat frequency, as female Tree Swallows with faster wings tended to start laying eggs earlier than "slower" females. Faster wings probably translates to more efficient foraging, which in turn would speed up the accumulation of springtime fat deposits that are necessary for producing eggs.

It's hard not to just sit by a nest box and watch these aerial acrobats for hours. But they're even more amazing on the southern wintering grounds. Tree Swallows are more sociable in winter, when many thousands gather into huge, swirling flocks about an hour before sunset, eventually landing to spend the night at a communal roost.

If you're interested in providing nest boxes for Tree Swallows, you can find all manner of nesting and life history information here.

The Last Full Moon of Winter

Last week's "Sap Moon" rises over the shoulder of Mt. Saint Nicholas, in Glacier National Park.

Different cultures give different names for each full moon of the year, with most of the names related to weather or agriculture. According to the Farmer's Almanac, there are several historical American names for last week's lunar spectacle.

March's full moon is called the "Sap Moon" and the "Worm Moon." That's because March is the time of year when the ground finally starts to thaw in the frozen north. And warmer ground means that the sap starts to rise from the roots of many trees, especially the maples back east that we tap for sap, which gets boiled down to make maple syrup. Warmer ground also means that earthworms migrate upwards and become active near the surface, leaving their castings on the surface starting in March.

This month's full moon is also known as the "Crow Moon" and the "Crust Moon." In March many of the larger bird species, like Crows, become more vocal as they begin courting and nesting. And the lingering patches of snow that melt during the day only to freeze again at night give us the the crunchy crust of March.

Next month, April's full moon is called the "Grass moon" and the "Pink Moon" (for the early-blooming pink phlox flowers). So last week's spectacle was supposed to be the last full moon of winter. Experience reminds me, however, that here in Montana more snow will fall on those flowers in April - and a little more in the "Planting Moon" month of May.