September 18, 2011
MIXED SANDPIPER FLOCKS
Here and there along the beach you come upon flocks of ten to a hundred fast-moving, toothpick-legged, nervous little brown birds with long beaks. They're sandpipers probing with their bills into the sand and into washed-up, moldering heaps of wave-deposited turtlegrass.
Most sandpiper species nest in the Arctic, at the northernmost fringe of North America's tundra. Even there the species are fairly similar to one another. Down here in their winter homes their plumages have lost most of any highlighting they had up north, and tend toward a general sameness; They all have subdued mottling or scaly, gray upperparts contrasting with plain, whitish underparts.
So, at first glance our sandpiper flocks look like they're made up of just one species. However, if you know that sandpipers often gather in mixed-species flocks and you pay close attention, you begin seeing subtle differences among the birds. In fact, our flocks here are nearly always mixed. Below I describe the citizens of one flock encountered last Tuesday.
THE SMALLEST SANDPIPER
Seawater pooled in a depression amidst an ankle-deep carpet of turtlegrass where at high tide the biggest waves washed across a sand barrier. About a dozen sandpipers preferred this relatively sheltered pool to the open, windy beach. Even without binoculars it was clear that one bird in the flock was different from others. It was brownish gray on top and white below like everyone else, but also it was conspicuously smaller and had yellowish legs instead of black ones like theirs. That's him at the bottom left at http://www.backyardnature.net/n/11/110918sl.jpg.
This is one of the easiest-to-identify of all sandpipers because it's the smallest species and has those yellow legs. It's the Least Sandpiper, CALIDRIS MINUTILLA. In the picture, the bird at the right and behind the Least is a Semipalmated Sandpiper, which is five inches long (12.7cm), which is smaller than a House Sparrow. The smaller Least is only 4-3/4inches long (12.0cm).
Other sandpipers in the flock waded in the pool, probing with their beaks. The Least foraged with a different strategy, keeping to the sides and picking in the turtlegrass where abundant springtails popped around the bird like tiny exploding kernels of popcorn.
Least Sandpipers overwinter throughout most of Mexico and as far south as Peru and central Brazil.
SEMIPALMATED AND WESTERN SANDPIPERS
The rest of the flock at the little wave-pool consisted of Semipalmated Sandpipers (CALIDRIS PUSILLA) and Western Sandpipers (CALIDRIS MAURI), seen at http://www.backyardnature.net/n/11/110918ss.jpg.
The flying bird in that picture, with its white wing stripes and dark rump feathers extending into the tail's center distinguish the Semipalmated and Western Sandpipers from other sandpiper species, but not from one another. In fact, it took me awhile to realize that in the picture the walking bird at the bottom left could be a different species from the one walking on the right. I thought I knew which was which, but I was so insecure about it that before naming them here I wrote to my friend David, master birder in Bermuda and absolute genius for oceanic and coastal species. He replied:
"...the left sandpiper on the ground is a classic adult Semipalmated and the right one on the ground is a classic juvenile Western."
David further explained that Westerns usually exhibit slightly downcurved bills with thickened bases, though many Semipalmated bills are nearly as long. He says that the clincher is to look for the Western's slightly larger body size, and in immature plumage the rusty reddish coverts at the shoulder. Adult Westerns usually show bolder streaking or speckling along their sides. He further points out that adults can be distinguished from immatures because adults have uneven, black blotches on wing coverts and backs. Immatures are always uniformly scalloped with buffy edges to their feathers.
Semipalmated Sandpipers, which my beat-up, 1966-issue of Robbins' Birds of North America describes as "probably the most abundant shorebird," occur here on the Yucatan Peninsula's eastern shore only during spring and fall migrations, though some overwinter on the peninsula's northern coast. The species winters from southern Mexico and the Caribbean to Chile and Argentina.
Western Sandpipers, in contrast, overwinter throughout most of Mexico, including all of coastal Yucatán. They winter from the southern US into northern South America.
David also confirmed as a Western Sandpiper the bird shown poking his long beak into his tail area at http://www.backyardnature.net/n/11/110918su.jpg.
That bird is beginning a period of preening by daubing his long beak onto his preen gland, or uropygial gland. The preen gland is a fleshy, small, oil producing, nipplelike nubbin typically at the base of a bird's back, about where shorter, fluffier back feathers yield to longer, stiffer tail feathers. During preening, birds smear oil from the gland onto their beaks or heads, then rub their beaks or heads over their bodies' feathers, oiling them up. The above sandpiper can be seen applying oil to his feathers at http://www.backyardnature.net/n/11/110918st.jpg.
The oil helps waterproof feathers and may be important in controlling the bird's external parasites. The vast majority of birds have preen glands; emus, kiwis, ostriches, and bustards don't.
Sandpipers aren't the only species arriving from the north in great numbers these days. On Wednesday morning dozens of Eastern Kingbirds, TYRANNUS TYRANNUS, began winging past my window as the sun rose. They were easy to recognize because as my old Robbins field guide says, "No other songbird has a complete, broad, white terminal band on the tail."
Despite having seen so many pass my window, once I was biking on the white sand road I couldn't believe how many perched atop Hurricane-Dean-killed trees in the mangroves. You can see four of them in morning sun at http://www.backyardnature.net/n/11/110918ka.jpg.
Just for the novelty of it you can see maybe a couple dozen more in a typical dead tree top at http://www.backyardnature.net/n/11/110918kb.jpg.
The thing is, in the mangroves hundreds of such trees exist, and nearly all of them visible from the road were just as busy with Eastern Kingbirds as the one in that picture. Moreover, once I settled into the mangroves I realized that the head-tall Red Mangroves themselves were thick with kingbirds, most birds casually drifting from tree top to top, occasionally snapping an insect from the air with a sharp click of its beak. There were tens of thousands of birds, if not hundreds of thousands.
These birds are just passing through, though. They nest in most of forested North America, but overwinter in South America, passing through Mexico and Central America only during spring and fall migration.
A POP-UP MANGO
While making the above photographs, in the bushes off to my left, a small, slender, rusty-hued bird popped up from dense cover onto a dead limb, then for a few seconds perched stiffly erect giving me the eye, before disappearing. I had time for one shot, which is at http://www.backyardnature.net/n/11/110918mg.jpg.
Once that image was on my laptop screen, what a surprise to see that it was a hummingbird. Moreover, it was a hummingbird colored unlike any I've seen around here.
Eventually work with the field guide revealed the little fellow as an immature Green-breasted Mango, ANTHRACOTHORAX PREVOSTII. Neither the adult male or female of that species display a reddish zone bordering the white throat area. Howell's illustration of an immature Green-breasted Mango's rusty sides is way off, not showing them gradually blending with adjacent colors, so maybe our photo will be helpful to later field-guide writers.
Green-breasted Mangos are distributed from southern Mexico to Venezuela and Peru.
PYGMY-OWLS HERE, TOO
In Querétaro and Chiapas we saw that Ferruginous Pygmy-Owls were common, and at Chichén Itzá they were abundant, calling with their monotonous weep-weep-weeps almost to the point of botheration. We have them here, too, weep-weeping from beside the mangroves, though not as prodigiously as at Chichén Itzá. There's one looking over his shoulder at us at http://www.backyardnature.net/n/11/110918py.jpg.
WORM SNAIL TUBE ON FLOTSAM
The other day a ham-size chunk of what I guess was expansion foam that had served as insulation between a boat's double hulls floated onto the beach. An animal's curled, cylindrical shell was attached to the foam. It was a lot like the worm tubes we saw inside a thorny oyster shell last week, but much larger. You can see the curling shell sticking to the foam at http://www.backyardnature.net/n/11/110918sn.jpg.
Another shot, from the front, showing a "false opening" at the side and what looks like a barnacle shell at the bottom left of the main hole is at http://www.backyardnature.net/n/11/110918so.jpg.
Volunteer identifier Bea in Ontario and I worked together on this but it took Bea to come up with the name EUALETES TULIPA, which is a sea snail, a marine gastropod mollusk in the family Vermetidae. Sea snails also sometimes are known as worm snails. Remember that last week's worm tubes were formed by segmented worms, like earthworms. What we have here is a mollusk, like snails and slugs -- a whole different phylum, phyla being like the phylum of animals with spinal columns (the chordates), the phylum of arthropods, the phylum of sponges, etc.
Lots of shells are similar to ours so we're not absolutely certain about the ID. However, Eualetes tulipa looks just like this, occurs in this part of the world, is known to attach to artificial substrates, and in some waters is considered an invasive species, so Eualetes tulipa is a good educated guess.
There's not much information available about Eualetes tulipa. However, now the world knows that it can ride on hardened expansion foam transported by ocean currents.
One of several native fig species found here is heavy with pea-sized figs nowadays, as shown at http://www.backyardnature.net/n/11/110918fg.jpg.
That tree was about 15 feet tall (4.5m) and was distinguished from other fig species in the area by its figs arising in pairs at leaf petiole bases (not singly) on longish stalks, or peduncles, and the figs were greenish-cream when immature, but dark red when ripe. The hairless leaves were three-veined from the base instead of having a single midrib. Fig taxonomy is a mess, maybe with certain species called one thing Mexico and something else elsewhere, but provisionally I'll park our current species under the name of FICUS OVALIS, a species occurring from here to at least as far south as Costa Rica.
The ripe figs are tasty, though often containing little worms. Eating the figs is almost like eating cherries without pits. A split-open one is shown at http://www.backyardnature.net/n/11/110918fi.jpg.
If you find a tree bearing figlike fruits but you're unsure whether they're really figs, break open the fruit. Figs have hollow centers and a soft, grainy texture. Also, check the stems. Fig trees, like other members of the Fig Family -- as well as sycamores and magnolias -- have "stipular rings," as shown at http://www.backyardnature.net/n/11/110918fh.jpg.
In that picture the ring is seen encircling the gray stem. It's a scar left from a stipule, which earlier encircled the stem. Stipules are modified leaves whose prime tasks are to protect young, delicate tissue by overlying them. Most stipules, once the delicate tissue they protect toughens up, fall away, leaving a scar. Most stipules are small and earlike, but fig tree stipules and their scars are unusually prominent.
Last May we saw that the local Poisonwoods, called Che Che'en in Maya (Metopium brownei), were producing a much greater number of flowers this year than normal. Now there's an unusual bounty of fruits. Before seeing the fruits you may want to review our Poisonwood page at http://www.backyardnature.net/yucatan/poison-w.htm.
Now take a look at the pretty panicles of red fruit glowing warmly in hot, late-afternoon sunlight at http://www.backyardnature.net/n/11/110918pw.jpg.
This week's migrating Eastern Kingbird gravitated into Poisonwood trees and I suspect they were feeding on these fruits. I read that the bird's winter food is heavy in fruits, such as those of Magnolia in Louisiana, which are red and fleshy like Poisonwood fruits.
AN ESPECIALLY SMALL, PINK-FLOWERED OLEANDER
Next to the main building a dwarf, pink-blossomed oleander is at its peak of flowering, as shown at http://www.backyardnature.net/n/11/110918om.jpg.
Most oleanders, which are NERIUM OLEANDER, are taller, up to 20 feet (6m), less bushy, and often have leaves with a grayer bloom. But there's a whole world of different kinds of oleanders, because of their prettiness, drought tolerance and ability to thrive in poor soil and fairly polluted air. Oleanders are among the world's most planted woody species, at least in warmer areas. Over 400 cultivars have been named, some with flower colors not generally seen in Nature. You might enjoy browsing a page featuring many oleander cultivars -- ones with evocative names like "Marrakesh," "Mary Constance," "Mrs. Kelso," "Sister Agnes" and "Pleasant's Postoffice Pink" -- at http://www.oleander.org/varieties.html.
If you have a highly modified oleander cultivar, how do you know you have a real oleander?
For one thing, an oleander's flower clusters, or inflorescences, arise at the end of branches and are of a particular form. They're known technically as "terminal branching cymes," with cymes being defined as more or less flat-topped inflorescences with their central flowers opening first, as shown at http://www.backyardnature.net/n/11/110918on.jpg.
Looking down a flower's throat you see what's shown at http://www.backyardnature.net/n/11/110918oo.jpg.
Like last week's yellow-flowered vine, Pentalinon luteum, there's a fuzzy thing hanging from the flower's mouth, plus, unlike the Pentalinon luteum, around the throat there's a fringe of slender, pink, fingerlike items. That fringe is something special distinguishing oleander flowers from many closely related types. It's analogous to the crown or corona on flowers such as daffodils. You can see how -- as in last week's Pentalinon -- the fuzzy things consist of hairy "anther appendages" arising from five anthers forming a tepee over a roundish stigma head at http://www.backyardnature.net/n/11/110918op.jpg.
You might enjoy comparing our view down the throat of our pink blossomed oleander with a similar look down the throat of a taller, tree-type, white-flowered oleander growing across the road, shown at http://www.backyardnature.net/n/11/110918oq.jpg.
Besides the color difference, the white flower's fringe is less finely divided. "Variations on an oleander theme... "
If you've been following our recent analyses of flowers you already know that -- because of those tepee-like anthers over the roundish stigma head -- oleanders are yet another member of the Dogbane Family, the Apocynaceae.
Oleanders are thought to be native to the drier areas of Eurasia and northern Africa.
HOW POISONOUS ARE OLEANDERS?
We've all heard that oleanders, like so many members of the Dogbane Family, are poisonous. This is a good time to figure out just how poisonous they are.
Oleander parts contain several compounds known to be poisonous, among them being oleandrin and oleandrigenin. These are "cardiac glycosides," which are used as drugs in the treatment of congestive heart failure and cardiac arrhythmia. They function by increasing the heart's force of contraction.
Rodents and birds don't seem to be much affected by oleander cardiac glycosides, but certain mammals, such as dogs, cattle and humans, do. A research paper on the Internet reports that "Nerium oleander leaves caused the death within 36 hours of 7 of 17 cattle which had access to boughs of the plant." A 1985 paper in the journal Annals of Emergency Medicine reports on a woman who died after drinking "oleander tea." A 1987 paper in the Journal of Analytical Toxicology reports on a woman who took it "both orally and rectally," and died.
So, people definitely can die from oleander poisoning. However, though several urban legends float around -- like the one relating how a Boy Scout troop was killed by roasting wieners on oleander sticks -- there are relatively few documented cases of oleander poisoning. A 1996 paper in the journal Toxicology concluded that, except for children who might be at greater risk because of their smaller body size, "human mortality associated with oleander ingestion is generally very low, even in cases of moderate intentional consumption (suicide attempts)."
When I break apart a fresh leaf from the pink-flowered oleander profiled above and with the tip of my tongue taste the broken part, it's so bitter that I can't imagine people accidentally or unthinkingly chewing enough leaf to harm themselves, unless they were bent on suicide. And I can think of many quicker and less disagreeable ways to die than by oleander poisoning.
ANTS ON THE ROAD
So, there's this line of army ants about five ants wide crossing the road. Do I bike over them, squashing a few, or do I stop, pick up the bike, and carry it to the other side? Cars and trucks that barrel down the road certainly don't stop, nor do I when I'm a passenger in a car. If I pick up my bike now but when I'm riding in an ant-squashing car don't stop, aren't I being inconsistent? And since the whole concept of ethical living is based on consistently behaving in agreement with ones morals -- one's beliefs about what's good and bad -- aren't I being immoral by inconsistently applying my pro-ant-life ethical principles?
Having lifted the bike across the ant line and begun peddling down the road, chewing on the possibility of my own immorality, I take up the matter that I don't even recognize the whole system upon which morality is based. I don't accept that things are innately and permanently either good or bad. I believe in evolving relationships, and that there's a seed of "yin" in every "yang," and visa versa. In other words, I go beyond mere immorality, clear into the realm of amorality. I have no morals at all!
Yet, I don't feel any wickeder than the next person. Something powerful and majestic does consistently lead me toward virtuous behavior. Something serves me the way "morals" serve others.
By the end of the road, I'm working on this idea: That maybe I'm guided by my sense of esthetics. Maybe I've been a vegetarian for over 40 years not because I find it immoral to eat flesh, but because to me with my particular background and nervous system eating flesh when you don't have to is just plain ugly. I lead a low-impact lifestyle not because I'm a goody-goody, but because it's beautiful to live simply, beautiful to be away from clutter, and to exist amidst quietness and peace.
But, who knows? It's only for certain that this morning on the white sand road is beautiful, and I'm glad I didn't squash those ants.
Best wishes to all Newsletter readers,