December 22, 2005
LEARNING TO BIRDWATCH
Vladimir, Katharine's son with whom I traveled to Chiapas last spring, is home after a summer in his native Switzerland, and I'm teaching him how to birdwatch. Mainly that entails learning how to use fieldguides, how to focus on a bird's most important fieldmarks, how to be systematic and mentally disciplined during the identification process, how to organize notes and lists, and what are the main bird groupings and their distinguishing characteristics. Last weekend we went on a birding and camping fieldtrip among the saltwater lagoons just inland from the beach north of here.
We had an unusual dry-season rainstorm at dusk but the tent kept us dry. During the night's first half, what a pleasure lying there in the darkness hearing the rumbling thunder, the surf on the beach about 300 yards away, and all the mysterious splashings, gurglings and bubblings of the briny water right next to the tent.
Not far from our tent site we'd encountered a beautiful Boa Constrictor about four feet long and we'd regarded that as a good omen, which it turned out to be. Around midnight the sky cleared and a nearly full Moon came out. I awoke sometime before dawn and the tent's walls were so luminous with moonlight I thought someone was shining car lights onto us, but then I remembered we were near no road. Through the mosquito netting I saw moonlight-charged fog silently gathering above the lagoon's silvery surface and out in the fog flamingo silhouettes moved about honking and splashing.
At dawn thousands of American Flamingos stood alone and in very small flocks 15-30 feet apart, from one end of the big lagoon to the other. Flamingos far outnumbered other bird species, of which there were plenty -- Great Egrets, Little Blue Herons, Black- necked Stilts, Wood Storks, White Ibises, Yellow- crowned Night Herons, White Pelicans, Neotropical Cormorants, various species of gull and tern, and more.
Despite so many things to look at we just couldn't take our eyes off the flamingos. How can such long, slender necks made of vertebrae, tendons and muscles be contorted into so many elegant configurations? Flamingos seem too fragile and ungainly to hold together under real life conditions, yet, here they were doing wonderfully well among storm-buffeted lagoons not even protected with a don't-shoot-the- birds sign.
In late morning the lagoons grew too hot to think in so we hit the beach and walked along it for a few miles. There were lots of new species for Vladimir to identify but even with breezes off the ocean by then it was just too hot and our brains were going mushy. We headed for a grove of coconuts I knew about, each of us plucked two large green nuts, and boy the juice in them was sweet and cool. As we drank, Brown Pelicans fished offshore, and neither do I understand how those big birds can crash into the water so violently without breaking their necks, or how they can live on as few fish as they seem to catch.
That afternoon the rain came again, catching us a few miles from town. But that rain was warm, the air smelled profoundly of fish, mud and tropical mould, the soaring thunderheads were dramatic and beautiful, and there were enough birdsongs to hear and flowers and butterflies to see, and everything struck us as absolutely perfect and right.
Last week I said that sometimes I find organisms washed up on the beach so strange that I can't even say whether they are plants or animals. That's nearly the case with one of the most commonly encountered things. This abundant item is a twiggy, much- branched, orange-red, more-or-less hand-sized article covered with short, blunt tubercles. Often its main stem bears white, stony fragments at its base, which I assume to be bits of the underwater coral reef from which it was torn. The item's stems, which have the consistency of very tough gelatin, barely can be snapped apart by vigorously applying a thumbnail. Vladimir and I saw lots on the beach this weekend.
To the inland naturalist this particular jetsam is most like the coral fungus found on decaying logs in the forest. You can see something much like this thing -- in fact it may be identical to it -- at http://www.solpugid.com/cabiota/Gymnogongrus.jpg.
The item in the above photo is a red alga of the genus Gymnogongrus. It's from the Pacific, so I'm hesitant to say it's the same as I'm finding here. However, a good number of oceanic plants and animals are "pantropical" -- found worldwide in tropical seas -- so this alga indeed might possibly occur in the Pacific as well.
In fact, when you reflect that our tropical waters seem in every respect identical to all other tropical waters, you wonder what's to keep all organisms such as the sea turtles mentioned last week from being pantropical. However the website linked to in that article clearly showed that some sea turtles are pantropical while others aren't. Clearly, the oceans are delimited with ecological barriers or historical events that aren't immediately obvious.
I Googled up the above Gymnopongrus picture by guessing that the thing I was finding was an alga, and using the keywords "alga, red, tropical." What a wonderful thing Google's "image search" feature is for itinerate naturalists!
Still, I'm not saying much by claiming to have found sprigs of red alga. About 6,000 red-alga species exist, of which only some 200 are found in freshwater.
The red algae comprise a taxonomic unit, the Rhodophyta. They come in every form from tiny orbs to large, leafy seaweeds, to coral-like "calcified coraline algae." Probably the best-known red alga is Porphyra, the so-called Red Seaweed cultured as food in Japan. Algae bear no flowers. Their reproduction is based on sperm flowing through water to reach eggs.
You can see several kinds of red algae and read college notes about their forms and life cycles at http://www.jochemnet.de/fiu/bot4404/BOT4404_23.html.
The other day as I sat on the beach one of the local fishing boats stopped right before me maybe 200 yards offshore, threw over a buoy with a red flag on it and attached to one end of a net, and then the two men in the boat proceeded to deploy the net, which was very long, with its top held at the water's surface by small floats, and its bottom kept down by small weights. The men let out about a quarter of mile of net parallel with the shoreline, then turned seaward for a minute or two, and finally turned back toward the buoy with a red flag. In other words, the net was laid in a U shape.
Arriving back near the buoy, the men began taking back into their boat both ends of the net, one man pulling in one end, the other man pulling the other. It was as if they'd thrown a net reaching a quarter of a mile away, and now they were pulling it all in. Remembering my vane struggle to keep straight the small netting placed over Fred and Diana's fruit trees this summer, to keep birds out, I think these fishermen must be artists of a sort to keep their net from tangling irretrievably.
It took them maybe half an hour to pull the entire net back into the boat, and from what I could see with my binoculars they didn't got more than five or six fish, and those didn't look big enough to keep.
In fact, as the boat headed off to a new spot offshore, I watched as one of the men gathered up the catch from their boat's floor and tossed each fish, one by one, overboard.
Within ten seconds of that first fish being thrown overboard gulls and terns were mobbing the boat, forming a white cloud all around it. Then a few Brown Pelicans joined the cloud, and some cormorants.
I can't imagine how the local fishermen even keep their boats running, much less make a living, with the modest catches I see them returning with. Nor can I imagine how so few fish thrown overboard could be of interest to such a large cloud of birds
I've never seen the water as low as when Vladimir and I walked along the beach last weekend. However, if I'd been calculating the gravitational fields at work that day, I shouldn't have been surprised at all. The almost-full Moon would have cued me to expect it.
For, tides are caused by the gravitational pull of the Sun and Moon. High tides come when the Earth's rotation places your part of the world directly above or below the Sun and/or Moon, and low tide comes when the Sun and/or Moon are near a horizon. The Sun, being so much farther away than the Moon, asserts only about 46% as much gravitational influence on us as the Moon, so the Moon is the main tide-maker, with the Sun just adding or substracting its offering, wherever it happens to be.
When we have a full Moon, as last weekend, that means that the Earth is more or less between the Sun and Moon -- the three bodies form a straight line in space -- so the gravitational fields of both of those bodies combine to create exceptional pull on the Earth's waters, causing high tides higher than usual, and low tides lower than usual.
You might think that with the Moon being on one side of the Earth and the Sun being on the other, the two gravitational fields would cancel one another out. It almost seems that way to me. However, I do know that during each lunar cycle, which is about 24 hours, 50½ minutes along, there are two tides, not one, and their highs and lows are almost the same. Therefore, the high tide on the side of the Earth opposite the Sun and/or Moon more or less mirrors the high tide on the near side, so if you want a high high tide, the relative positions of the Earth, Sun and Moon aren't so important. What's important for especially high and low tides is just that all three bodies are in a straight line.
Interestingly, back at the lagoons we'd just left, the water was pretty high. That was because the channel between the lagoons and the sea was so narrow that water couldn't flow through it fast enough to keep the lagoons' water level in phase with the sea.
There's always such a strong current along that beach that I just stay out of the water. On this north- facing beach the current flows from east to west. That also makes sense when you view the Gulf of Mexico's circulation patterns shown in the US Navy's chart of oceanic currents at http://www.learner.org/jnorth/images/graphics/n-r/OceanCurrentsUSNOO.gif.
WINTER SOLSTICE AND THE YUCATAN
Back when I was issuing this Newsletter from the woods outside Natchez, Mississippi I always made a big deal about the Winter Solstice taking place this time of year. The solstice was important because -- at least from the perspective of this naturalist near Natchez -- it seemed that on that date the current year's natural cycle ended and a new one began.
The precise changeover took place at the moment when days stopped getting shorter and began getting longer. What pleasure I had finding "signs of spring" already on the Winter Solstice date, and what a delight when, just two or three weeks after the solstice, it really FELT as if days were getting longer, and that a gloriously warm, green, luxuriant spring was avalanching toward us.
Down here there's not much difference in the length of "summer" days and "winter" days. In fact, the concepts of "summer" and "winter" don't make much sense because here the big differences are between dry and wet seasons. You can see what I mean on the graph showing monthly temperature and precipitation data for Mérida, the main town here, at http://www.backyardnature.net/yucatan/climate.htm
So, right now, for me, there's no sense of the annual cycle coming to an end and beginning anew with the solstice. What I really feel is the dry season gradually getting underway. Herbaceous plants are starting to show the strain of lack of rain, though they're not turning brown yet. Some of the trees who lose their leaves during the dry season, to conserve water by cutting down on water evaporation from leaves, are losing their leaves now -- the Guanacastes, strangler figs, the Flamboyáns.
If I happen to be here when the dry season ends with the first big rains, maybe around late May, then I'll celebrate the beginning of the new annual cycle for here, for at that time there'll be so many new germinations, blossomings, hatchings and emergings from dust that it'll be the equivalent of "spring avalanching forth," maybe even with more exuberance than I've chronicled in Mississippi.
In my life I've benefited enormously from consciously and sincerely celebrating whatever natural rebirths, rededications, and general startings-all-over-again I could identify. In fact, it seems to me that the human spirit is programmed so that it requires an intimacy with the cyclical seasons, and human psychology is structured to find the greatest peace when abiding dependable, natural routines.
It's unfortunate that the calendars we've ended up with only approximately recognize the real natural restarting points of the Earth's annual cycles. They do at least declare a new calendar year, and that's a step in the right direction.
So, because my roots are in a culture evolved where the Winter Solstice traditionally was a big deal, and these are the days of the Winter Solstice, I say this: Wherever you are in the world and whatever annual cycle you happen to identify with most, I wish you either a happy conclusion to your current cycle, or a happy beginning of a new one.
If I'm here when the rainy season cracks open, you'll hear all about it, and we'll have our own jolly "New Year" then, maybe celebrating with emerging frogs.
Best wishes to all Newsletter subscribers,
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