Almanac: Evening Idyll
Paddling with Sean Paradiso on Lake Warner. Photo: Stephen Braun
By Stephen Braun
It was an ordinary evening on Lake Warner in North Hadley this past Tuesday. A friend and I paddled under calm, cool, overcast skies. Nothing special.
About a dozen Canada geese were paddling about near the dam. Why have these birds not joined their brethren in the typical summer breeding grounds in their namesake country? They wouldn’t let us get near enough to ask, rousing themselves when we approached with a cacophony of honking and a great slap-slap-slapping of webbed feet running on the surface of the water as they worked to get their heavy bodies airborne. It’s possible this crew will stay put all summer, breeding and raising their young without the usual migration. But it’s more likely that these are simply stragglers using the lake as a rest stop on their way farther north.
We paddled on, and a belted kingfisher scolded us from a branch hanging over the water. They love those kinds of perches because it allows them to watch for the fish that make up much of their diet. If a potential meal swims into view, the kingfisher will plunge into the water using its distinctively long beak to grab its prey and carry it back to the perch for consumption, which often means swallowing the victim whole.
As we glided eastward the sound of traffic faded. Often we would stop paddling and drift, enjoying the quiet and the background music of mourning doves and red-winged blackbirds.
Some eastern kingbirds, flying with the speed and precision of swallows, zoomed low over the water hunting insects, although that evening was blessedly free of the wee beasties that like to dine on human flesh.
A great blue heron, its considerable bulk supported on a single reed-like leg, eyed us warily as we passed. He or she (the sexes are very difficult to tell apart) was probably trying to stay warm with its unipedal posture. That’s the theory, anyway, and it certainly makes sense since bird legs are typically uninsulated. The arteries and veins of bird legs run very close together in a pattern called “rete mirabile” (Latin for “wonderful net”). This system warms blood returning from the cold feet and allows the feet to stay quite cool without unduly chilling the rest of the body. Still, that adaptation can only get you so far. Many birds, not just herons, will stand on one leg, tucking the other one up close to their bodies to further reduce heat loss. This heron seemed unfazed by our approach, although we didn’t get too close, in deference to its seeming contentment.
Toward the eastern end of the lake, where it narrows into the Mill River, I noticed some small bubbles rising in the water just off my bow. Then the bubbles became a trail, moving ahead of me. I could see nothing below the surface, and no ripples betrayed an animal such as a beaver or muskrat that might be swimming just below the surface. After a minute, the trail of bubbles stopped, mysteriously. The bubbles were very small, not like those you’d expect from some animal exhaling as it swam. So I suspect that a large bottom-dwelling fish or turtle was swimming ahead of me, stirring up the muck as it went, releasing a trail of trapped gasses. But who knows? Nature is full of these kinds of miniature mysteries.
We dawdled a bit where the river became impassable without leaving the boats, then headed back. The air at that end of the lake was redolent of pine, ferns, and a clean marsh smell and evoked memories of wilderness paddles in the Adirondacks. How fine to feel so far from civilization when, in fact, we were surrounded by it.
Midway back we caught up with a pair of common mergansers, the brown-headed female sporting a classy rearward crest of feathers, the male a study in contrast, with a jet black head and back and snowy white breast and lower body.
Then, as we passed the two large beaver lodges adjacent to the small island at the western end of the lake, a mature bald eagle flew low over the water, heading northwest, flapping heavily, with a fish clutched in its yellow talons. I’ve seen enough eagles to know that sometimes these creatures can look quite ratty indeed, and they have a deadly seriousness to their disposition that I find a bit unnerving. Nonetheless, they are simply magnificent, and I can’t help thrilling at a close encounter.
Bald eagles are worth a column of their own, but I’ll just mention one aspect of their physiology I find amazing: their visual acuity. Eagles have roughly a million cells per square millimeter packed in the fovea of their retinas, compared to about 200,000 cells/mm2 in humans, and they can see a wider spectrum of colors than we can, including ultraviolet. What I wouldn’t give to see the world through an eagle’s eyes for just a few minutes!
We watched the eagle depart, then finished the paddle. It had been a perfectly ordinary evening on Lake Warner…and perfectly extraordinary.
A physics addendum to (yet another of!) Steve’s wonderful pieces (I’m getting writer’s envy ;-):
Since blue (and violet and ultraviolet) light is at shorter wavelength end of the spectrum, it makes sense that “bluer-seeing” eagle retina cells are smaller and more densely packed than the “redder-seeing” human ones. Indeed, the wavelengths of “red” and “violet” light are roughly 0.7 and 0.4µm, respectively which is roughly the range of diameters of each retinal cell presents to the optical surface of the retina (roughly: a “receiver” can’t be much smaller than than what’s “received”). But a cell can’t function if its volume is too small, and so retinal cells (like nerve cells) are extremely prolate: they’re roughly 100 times longer in the direction perpendicular to the optical surface of the retina!
Anyway, I wanted also share a puzzler with Steve and all his readers:
What color is our Sun, and how can you tell (hint: don’t look at the Sun, which is dangerous, but it’s OK to look at the grass, the trees, and most other plants)?
Thanks for that addendum Rob…a fascinating aspect of anatomy! As for the sun, I have my thoughts, but will wait to see if anybody ponies up some ideas. Coincidentally I was going to write about the predominance of green in the plant world but, as always, that’s more complicated than it appears so I shelved that idea. I always thought that if you tried to grow a plant under a pure green light it would quickly die because leaves absorb blue and red and reflect green. That’s kinda, sorta true, but it’s way more involved/subtle than that.