August 10, 2007

BIRDS IN MEXICO CITY
Last weekend I needed to visit Mexico City so at 11 PM Friday night I caught the overnight bus and arrived there at 4:30 AM. Even at such an hour the huge Northern Bus Terminal was so busy that I chose to wait outside until gates to the Metro, or subway, opened. At an official elevation of 7349 feet (2,240 m), that morning it was 58° F, which felt pretty cold to my body long acclimated to tropical lowlands.

The Mexico City metropolitan area, which includes huge and densely populated suburbs, supports a population of over 19 million. That makes it the most populated metropolitan area in the Western Hemisphere, and the second-most populated in the world, after Tokyo.

Still, parks, college campuses and certain upscale residential areas often are graced with shade trees. Moreover, now during the rainy season most afternoons a storm cleanses the air and keeps the dust down, so air pollution isn't nearly as bad as during the winter dry season.

You'd be surprised what birds you can see even in the heart of Mexico City. Paseo de La Reforma, the city's "Main Street" if there is one, is lined along its entire length by well maintained plantings of trees.

Often I saw House Sparrows, Pigeons, and heard House Finches and Great-tailed Grackles singing. Inca Doves -- small, gray ground-doves with long tails and a conspicuous mottling that made them appear "scaled" -- landed on the sidewalk before me looking as if they'd be glad if I thumped a breadcrumb their way. Barn Swallows, present year-round in central Mexico, swooped low over a little park-pool as if it were a farmer's pond in the country. In quieter areas a little off the Reforma, early in the morning, I even heard American Robins singing. They're present in central Mexico and the Sierra Madres of both coasts year-round.

During the winter of 1996/1997 I made a birding trip through Mexico, from the northern border at Juárez, in a sand-dune desert, through mountains, along the coasts, in dense forests, and up a high volcano. Midway my journey I hurt myself and ended up spending a week in a friend's unfurnished apartment in the heart of Mexico City, recuperating. You can read my birding notes from those invalid city days at https://www.backyardnature.net/mexbirds/09mex_df.htm.

If you read that report you'll see that in a tiny park near the apartment, wedged between very busy, loud highways, and with only a handful of trees, I managed to see such interesting species as Berylline and Broad-billed Hummingbirds, Bewick's Wrens, Rufous- backed Robins, Blue-gray Gnatcatchers, Ruby-crowned Kinglets, Wilson's and Yellow-rumped Warblers, American Redstarts, and Bronzed Cowbirds.

Some nice pictures and a much more extensive list of birds spotted on wooded slopes above Mexico City, in Desierto de los Leones Recreational Park, appear at http://www.charliesbirdblog.com/~charlie/MEX26mar05/MEX26mar05.html.

Wikipedia's extensive, illustrated page on Mexico City itself is at http://en.wikipedia.org/wiki/Mexico_City.

*****

CHAPULTEPEC PARK'S PALE & MOTTLED SQUIRRELS
1600-acre large (647 ha) Chapultepec Park is twice the size of New York's Central Park. It occupies land on which the Aztecs lived as early as 1200 AD. Spanish King Carlos V declared the area a nature zone in 1537. Wikepedia's illustrated page about the park is at http://en.wikipedia.org/wiki/Chapultepec.

Since the meeting I needed to attend lasted only a couple of hours I had most of last Saturday free until my bus back to Jalpan left at 9:30 PM. I spent much of the day wandering all through Chapultepec Park.

Squirrels there are as unafraid of humans and eager for a handout as any I've ever seen. Several times I saw kids freak out when they got to see a squirrel really close up. They're the Red-bellied Squirrels, SCIURUS AUREOGASTER, I told you about in the uplands here, in the July 20th Newsletter.

Instead of being gray squirrels with well defined, brightly rusty underparts like ours, Chapultepec Park's squirrels come in many variations, ranging from the standard design to nearly all-white individuals, and many have blotchy patterns, often with rusty spots above as well as below.

This color variation in a wild animal is worth thinking about.

Darwin pointed out that wild animals tend to look alike but domesticated ones often show variations in color and pattern. For example, wild Rock Doves, the ancestors of city pigeons, usually look alike, but the plumage of city pigeons, considered to be the same species as wild Rock Doves, is very diverse.

The usual explanation for this is that in nature there's such a struggle for survival that evolution has equipped each species with an optimum behavior and appearance for survival. Any deviation from that optimum puts an individual at greater risk than the general population, so genetic information allowing the deviation soon disappears -- when the carriers of the information die.

But when an organism is domesticated, many pressures are removed -- those from predation, for example. Once the pressures are removed, then there's less "culling" of those individuals looking and behaving in nonstandard ways. A wild Rock Dove with a white feather in a wing is more visible to predators than his flock mates but a white feather in a domesticated pigeon means nothing, so the genetic information permitting white feathers and maybe other features even more atypical get passed on.

So, since 1537 when Chapultepec Park's squirrels found themselves in a protected area, genes of the park's squirrel population have had many selective pressures removed, their genes have been at greater liberty to experiment, and today's pale and blotchy squirrels have resulted.

In human populations the pressures encouraging genetic conformity also have been removed. In fact, because of medical advances, you could say that now human evolution has changed direction. People who in the past would have died young with genetically based diseases now pass along their predispositions to future generations. What does this mean for the future of human evolution, and what, if anything, should be done about it?

A controversial and thought-provoking webpage on this very subject, suggesting that "The rate of human descent is perhaps thousands of times faster than the rate of its ascent" can be visited at http://www.onelife.com/evolve/degen.html.

*****

SCORPION EXUVIA
Scorpions, like spiders, have "outside skeletons," or exoskeletons, so as they grow they must molt one husk after the other, the molting process being known as "ecdysis." The molted exoskeleton is called an "exuvia" (plural exuviae). So, the other day, atop the switch that opens the gate, which several of us grope for each night to let in or out those without keys, I found the neat little scorpion exuvia shown at https://www.backyardnature.net/n/07/070810ss.jpg.

Probably this is the exuvia of the same species I profiled in the July 6th Newsletter, CENTRUROIDES GRACILIS, known as the Slender Brown Scorpion or Florida Bark Scorpion, and whose portrait remains at https://www.backyardnature.net/n/07/070706sc.jpg.

An interesting feature of that exuvia is that it bears what appears to be an intact stinger, or "telson." The handlens shows a perfectly preserved stinger, but I assume that it's empty of the glands producing venom. Scorpions typically require between five and seven molts to reach maturity.

While confirming the above fancy scorpion terms I learned that most scorpions are slightly fluorescent, something discovered by geologists in Arizona in the 1940s. In the 1970s only about 600 scorpion species were known to science but now over 1520 have been named, thanks mostly to researchers knowing to look for new species at night using "UV flashlights."

*****

DATE PALMS ALONG THE REFORMA
Last Saturday I hiked the tree-lined, 7.5-mile long (12 km) Paseo de la Reforma both ways. One reason I'd do that is because despite its being such a busy thoroughfare it's lined on both sides by trees, as you can see in the skyscraper-taken photo at http://en.wikipedia.org/wiki/Image:Torre_Mayor_005.jpg.

There's a good variety of trees, too. There are eucalyptuses, pines, cottonwoods, Sweetgums, ashes, junipers, pepper trees (genus Schinus) and more. Particularly I enjoyed the palms, one of which you can see at https://www.backyardnature.net/n/07/070810pc.jpg.

That's the Canary Island Date Palm, PHOENIX CANARIENSIS, a true native of the Canary Islands off the Atlantic coast of North Africa. It's such a beautiful and hardy tree -- able to survive dry spells, cold snaps, and apparently air pollution -- that it's planted in tropical and semitropical areas worldwide, including along streets in California and Florida.

Being in the genus Phoenix it's a "real" date palm, but it's not THE Date Palm, which is Phoenix dactylifera. The Canary Island Date Palm does produce edible dates but they're so small and their flesh is so thin that few bother to eat them. Phoenix canariensis can grow up to 60 feet tall, though usually what you see is only half that size.

In the photograph the diffuse, orangish, brushlike items among the tree's fronds are maturing fruit clusters. The fruits are only about 3/4-inch long, compared to a date, which might get two inches long.

Besides having smaller fruits, Canary Island Date Palms differ from "real" Date Palms in that Date Palms sprout from their bases. Unless someone is cutting the extra sprouts back, Date Palms appear in clusters. Canary Island Date Palms, in contrast, arise on solitary trunks.

Date palms as a group are fairly easy to distinguish from other palm kinds. First, their fronds are featherlike, instead of fanlike, as in the palmettos. After noticing that, the only other feature to look for is to see that the fronds' lower leaflets, or pinnae, are represented by stiff, long spines instead of regular soft, wide blades. The spines are substantial, hard and sharp, so when you see them there's no doubt about it.

*****

THE BEAUTIFUL-STAMEN BUSH
Not far from the Canary Island Date Palm shown above, next to the entrance to a bank, I snapped the photo at https://www.backyardnature.net/n/07/070810cl.jpg.

That a flowering branch the head-high Lemon Bottlebrush, CALLISTEMON CITRINUS, a member of the Myrtle Family, along with eucalyptuses, Allspice and of course myrtles. The genus name Callistemon derives from the Greek roots calli for "beauty," and stemon for "stamen" -- "beautiful stamens."

In fact, in the picture, the bright red, slender items so curiously arising in mid-stem are mostly the male stamens composed of red, stemlike filaments atop which reside tiny, pollen-producing anthers. Inside each stamen cluster there's a similar-looking slender, red style (the necklike extension of the ovary) and atop each style there's a tiny stigma, which is were pollen grains from other flowers germinate.

Especially in the picture's top stamen-clusters you can distinguish the single styles because they rise a tiny bit above the stamens, are a little thicker than the stamens' filaments, and their yellowish stigmas are flat-topped platforms instead of baglike anthers releasing pollen. The style is longer than the filaments because the flower "wants" the approaching pollinator to deposit pollen from other flowers on its stigma before entering the tuft of stamens below searching for nectar.

Crushed leaves of this plant have a distinctly citrus aroma. Native to Australia but planted worldwide, you can imagine how this species attracts hummingbirds.

*****

QUESADILLAS & HUARACHES
While snacking from sidewalk stands in Mexico City I photographed a couple of my meals. Remembering from a while back the controversy that arose when I called something I'd eaten and photographed a burrito, here I'll just say that the things showed in the photographs are called by the names they were sold under when I bought them.

First, let's look at the quesadilla, which is at https://www.backyardnature.net/n/07/070810qd.jpg.

The bluish-black item upon which red hot-sauce was smeared before white cheese was melted atop it and later doused with green hot-sauce is a genuine corn tortilla made from central Mexico's traditional blue corn. Here in Querétaro I never see blue corn tortillas. I can't say that blue tortillas taste much different from white or yellow ones, but I always get a kick eating blue tortillas anyway.

The next item is a huarache, shown at https://www.backyardnature.net/n/07/070810hu.jpg.

To make the huarache an oblong corn tortilla has been stuffed with bean paste, fried in oil and garnished with green hot-sauce and shredded white cheese. In Mexican Spanish the word huarache refers to the traditional Mexican leather sandal, which has a similar shape.

*****

A RAIN IN MEXICO CITY
Late last Saturday afternoon I was killing time before my 9:30 PM bus back to Jalpen left by wandering backstreets in Mexico City's central zone. As it should during the rainy season, around 5 PM dark clouds gathered on the horizon in preparation for the afternoon storm.

As storms went, it turned out to be a mild one. Still, I enjoy just about any storm, especially when it's in a new environment.

First the wind came, not real strong, but strong enough to blow yellow cottonwood leaves (probably the much-planted Fremont Cottonwood, Populus fremontii) down streets along with swirls of dust, discarded napkins, Styrofoam junk-food boxes, etc. Here in mid summer with no hint of autumn in the air, why should yellow cottonwood leaves so conspicuously blow down Mexico City's backstreets? My main association with windblown, yellow cottonwood leaves in one time when I was camping in backcountry Paria Canyon in arid southern Utah and a wind came driving yellow cottonwood leaves across the red-rock landscape.

I savored the juxtaposition of memories of Paria's yellow cottonwood leaves in such profound isolation, with these so very urban yellow cottonwood leaves. This kind of savoring, associating events and things in one place with those in another of long ago is a kind of mental exercise I do more and more as I grow older. Maybe that's what really old folks are doing when you see them just sitting, surprisingly contentedly, long, long hours.

When the cold rain began I joined a mumbling old street-man who'd taken his bagged belongings into a corner the rain couldn't reach. Over his shoulders he wore a plastic garbage bag with a hole in the bottom for his head, like a poncho. But wind usually changes direction during a storm's latter half, and when it did it began drenching us. Mumbling to the sky the old man moved into an alley a bit too seedy looking for me, and I went to beneath a closed taco-stand's overhanging porch.

From there I saw lots of things, all kinds of people doing everything from cringing in corners as if the rain were killing them, to those putting on a show ignoring the rain, getting absolutely drenched, like two guys washing their own portable taco stand. A car hit a pothole full of rainwater splashing four women dressed for Saturday night on the town, and they all laughed uproariously.

I saw lovers making the most of intimate moments in the rain, dogs grinning as rain dripped from their tails, taxi drivers suddenly aware of their importance with heroic looks on their faces, a fat old woman in a purple dress watching everything through a coffee shop's window, half smiling, indulging the pleasure of such a special moment.

I can see how city people would love their city's moods and complex manners of beings, and how they might even claim that in a city one can learn all the lessons, see all the paradigms, and experience all the feelings that I, for instance, go into Nature to find. The city is an ecosystem, too, with its unfathomably complex web of interconnecting, interdependent parts, fast-evolving feedback mechanisms, and transcendent, soul-nourishing, driving dynamism.

But, there is one thing Nature has that no city does, and that is a proven record for sustainability. Even if a city has all the elements that can inspire and engage a healthy human soul, those elements are never present in the proper proportion for sustainability. For example, cities recycle resources, but not as single mindedly and efficiently as nature. Cities have their music, but the themes and rhythms can change almost overnight. They're not at all eternal, like Nature's music of wind-in-trees, rain-in-the-forest, morning bird-chorus, and the exquisite music of life-evolving-forward.

In a way, urban structures and institutions parody Nature's. The parody can be entertaining and informative but, for the long haul and to inform one's spirituality, one must summon the more profound wisdoms of Nature.

*****

Best wishes to all Newsletter subscribers,

Jim