JIM CONRAD'S
NATURALIST NEWSLETTER
Issued from Mayan Beach Garden Inn 20 kms north of Mahahual
on the Yucatán Peninsula's eastern coast just north of the Belize border,
in the state of Quintana Roo, MÉXICO
(N18°53'16.36', W87°38'27" )

October 23,  2011

MOORHEN DOMESTIC SCENE
At http://www.backyardnature.net/n/11/111023mh.jpg you see a family of Common Moorhens, GALLINULA CHLOROPUS, at a mangrove pond edge beside a dense stand of Sawgrass. A softly clucking adult with a bright red beak and frontal plate perches on a fallen tree trunk alertly watching as three immatures preen and forage at the Sawgrass's edge. Common Moorhens occur in the Yucatán only during the Northern winter, though they're permanent residents in most of upland Mexico, so these birds are recently arrived.

In similar habitats in the Yucatán closely related and similar looking Purple Gallinules and American Coots also can be seen during the winter. Moorhens can be distinguished from them at a distance by the white body stripe below the wings.

Moorhens are among the few bird species with nearly "cosmopolitan" distribution -- they occur planet-wide, though not in Australia and colder and desert regions. In the Americas they summer throughout the eastern US, moving south during the winter, but overwintering on the US's Deep South coast. My old field guide calls them Common Gallinules, but the trend is toward using "Moorhen" in deference to the older European usage.

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MOUSE-EATING YUCATAN JAYS
Early one drizzly, foggy morning this week as I approached the end of a road leading to a coastal lagoon I came upon a flock of about ten loudly complaining Yucatan Jays. I thought they were just unhappy to see me until I noticed that at least some of their agitation seemed to arise from one of their members holding something in its beak, as shown at http://www.backyardnature.net/n/11/111023yj.jpg.

The jay had a dead mouse! Jays belong to the same bird family as crows and ravens, and most species in that family are omnivores, so this wasn't a big surprise. Still, one wonders whether the jay killed the mouse, took it from a predator, or just found it. For fifteen minutes the bird in the picture simply perched in different places with the mouse dangling from his beak, even when a mostly white juvenile bird approached pitifully begging to be fed with flapping wings and feed-me whines. Eventually the whole flock flew into the mangroves, the mouse still dangling.

Omnivory in a species is regarded as indicating relatively high intelligence. In fact, members of the Crow Family display brain-to-body weight ratios equal to that of the great apes and whales, and only slightly lower than humans. When compared to dogs and cats in an experiment testing the ability to find food according to three-dimensional clues, members of the Crow Family proved the most adept.

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HERON IN THE DRIZZLE
The early part of this week was dark and drizzly with frequent brief showers that moved in off the Caribbean throughout the days. In the mangroves I met an immature Little Blue Heron all scrooched up against the rain and chill, his looks expressing the mood at http://www.backyardnature.net/n/11/111023hr.jpg.

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BIRDING WITH PHOTOSHOP
In such darkly overcast weather often the views I got of birds this week amounted to no more than black silhouettes against a gray but glaring sky. Still, when a small falcon swooped overhead and landed atop a nearby tree, despite seeing no colors at all it sure looked like an American Kestrel, FALCO SPARVERIUS.

Several falcon species occur here so I needed to confirm that this wasn't something rare. Though through the binoculars all I saw was a black silhouette, I photographed the bird. Once the image was on my laptop screen I went into the PhotoShop image-editing program and very much overexposed the image by grossly increasing both brightness and contrast. Before and after shots can be compared at http://www.backyardnature.net/n/11/111023kl.jpg.

The overexposed picture won't win any photography awards but at least it shows the "whiskers" on the bird's face and a rusty back, and that's enough to confirm the bird's identity as an American Kestrel. Kestrels are present in the Yucatán only during the Northern winter, so this bird also has just arrived.

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WARBLER IN THE RAGWEED
Of all the wood-warblers who once awed me with their colors, movement and singing during spring migration up north, one of the most memorable species was the Black-throated Green Warbler. Sometimes in untold numbers they filled cool, spring forests with their wheezy EEE-EEE-uh-EEE calls, which besides being majestic were hilarious to hear. Many warbler calls are musical and complex, but these Black-throated Greens just said EEE-EEE-uh-EEE as if they had cockleburs in their throats, and they said it constantly, dawn to dusk, thousands of birds calling from every direction...

I remembered that this week when I saw what's at http://www.backyardnature.net/n/11/111023dd.jpg.

That's a Black-throated Green Warbler restlessly foraging for tiny arthropods atop a carpet of ferny-leafed Coastal Ragweed. His plumage only now is beginning to fade from summer's bright breeding plumage. Like so many other birds being seen these days, this bird has just arrived from up North. He breeds mostly in southern Canada and the adjacent US, and south through the Appalachian uplands. The species overwinters in lowland tropical Mexico south to central Panama.

Down here sometimes during migration I do hear the old familiar EEE-EEE-uh-EEE, but it's just one phrase, and then silence.

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RESHUFFLING WARBLERS
This week Jarvis in North Carolina sent us a link to a page describing big changes in the technical or binomial names of American warblers. For example, the above Black-throated Green Warbler, which as a teenager I learned to call Dendroica virens, and which all my field guides still call Dendroica virens, now is to be called Setophaga virens.

English names will remain the same, but the Latin names of many of our most common and beloved warblers will change, plus there'll be some changes in the sequence in which birds appear among our field guide pages. These warbler name-changes are discussed here.  

The changes result from new understandings wrought from gene-sequencing studies. The idea is that technical names as well as the taxonomic categories to which we assign living things should reflect the actual way the organisms evolved through time. All the species in a genus, for instance, should have arisen from a common ancestor, the first species of that genus to appear on Earth.

In the past taxonomists guessed at relationships, based on outward appearances. Now genes reveal the actual evolutionary histories, based on the assumption that the more genes two taxa share, the more closely related they are. A "tree diagram" visually showing the supposed evolution of American wood warblers can be accessed here.

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CHRISTINA'S CROCODILE
The other day Newsletter reader Christina near Tulum in the Yucatán sent me some crocodile pictures, asking if I thought she had an American or a Morelet's Crocodile. It was hard to say from the pictures but in the end I figured it was probably a Morelet's, based mainly on the fact that its snout seemed wider than the American's, plus at her inland, swampy location near Tulum Morelet's is what you'd expect. Christina has put together an interesting and well illustrated blog about her family's experience with the croc here.

American Alligators are completely different from crocodiles. You can't see an alligator's teeth when its mouth is closed, but a crocodile's lower teeth are always visible. Also, the alligator's snout is much broader than a crocodile's.

American Crocodiles occur from extreme southern Florida south spottily along the coasts to northern South America, so the Yucatán fall within that distribution area. Morelet's Crocodiles occur only in southern Mexico, Belize and Guatemala. Along the Yucatán's eastern coast American Crocodiles occur mostly in mangroves, coastal lagoons and sand banks, while the Morelet's is found mostly inland in sinkholes, ponds, and flooded savannas.

If you want to know which of our two croc species you have, there's a way to figure it out. Keeping in mind that "maxillary teeth" are those arising in the upper jaw and that they're numbered from the front, Jonathan Campbell in Amphibians and Reptiles of Northern Guatemala, the Yucatán, and Belize tell us the following:

The American Crocodile's snout width at the tenth maxillary tooth is less than or equal to 70% of the distance from the base of the tenth maxillary tooth to the tip of the snout. In contrast, the Morelet's snout is wider -- at the tenth maxillary tooth the snout's width is greater than or equal to 75% of the distance from the base of the tenth maxillary tooth to the tip of the snout.

The tenth maxillary tooth coincides with the snout's constriction about midway the snout's length.

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CRAB TUNNELS
Within a few feet of the water most of the beach in our area is perforated with a few to many holes about right for a golf ball to roll into. You can see some at http://www.backyardnature.net/n/11/111023cb.jpg.

At the picture's lower, right, those are Ghost Crabs, OCYPODE QUADRATA. You can see Ghost Crabs closer up at http://www.backyardnature.net/yucatan/ghost-cb.htm.

In our first picture the two crabs had emerged from the same hole. Also, the outside crab had exited that hole but then entered another. These observations got me curious about Ghost Crab tunnels.

In Wayne and Martha McAlister's Life on Matagorda Island, an online "Google Book," I learn that Ghost Crab tunnels enter the sand at 45° angles and are directed so that they catch the onshore breeze. Often two tunnels join into a Y, possibly to create a draft through the lair. Other tunnels are simple Ls or Js, the bottoms enlarged so that the crab can rest and turn around during the day when normally it's belowground. The tunnels descend to just above the water table, and usually there's just one crab per tunnel.

Ghost Crab tunnels aerate the sand, but also newly hatched sea turtles tumble down them. Ghost Crabs prey on both turtle eggs and recently hatched turtles.

A study in Malaysia with a different species of ghost crab found that when the crabs tunneled into turtle nests they would break open several eggs. This began a sequence of events normally resulting in the entire clutch being destroyed -- though the crab may actually eat only a few eggs. The crab's tunnel serves as an entry point by other predators, such as ants and fungi, plus diseases affecting the whole nest arise from the broken eggs.

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POLYDAMAS
At http://www.backyardnature.net/yucatan/mariposa/butt099.jpg you see a Polydamas Swallowtail, BATTUS POLYDAMAS, a swallowtail without a tail like a swallow's. Volunteer identifier Bea in Ontario figured it out. I've been trying to photograph this species for the last six months but this is one of those butterflies that keeps moving. Then Wednesday this one turned up with his proboscis probing sand just a couple of feet from the water, maybe sopping up salt.

Polydamas Swallowtails are widely distributed from southern Texas and Florida south to Argentina, plus sometimes they stray outside their usual distribution area. In the US they've been seen as far north as Kentucky and Missouri.

Polydamas caterpillars are listed as eating leaves of pipevines, which are poisonous vines in the genus Aristolochia. Butterflies whose caterpillars eat pipevines are thought to be bitter to potential predators, and poisonous themselves. I've not seen pipevines growing here. However, adult Polydamases take nectar from lantanas, and we've seen that here lots of lantanas (the "Wild Sages") are flowering right now.

By the way, that nice name Polydamas means "trojan warrior." The name originated as a Greek name given to boys.

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HURRICANE-GRASS
In the middle of a sandy trail leading through mangrove into a coastal lagoon a distinctive-looking, pincushion-like, grasslike plant turned up, as shown at http://www.backyardnature.net/n/11/111023fm.jpg.

Its flower cluster, or inflorescence, is shown at http://www.backyardnature.net/n/11/111023fn.jpg.

Most inflorescences of this species do not have vertical, green "involucral bracts" rising above them as this one does. Usually such bracts are shorter than the inflorescences and thus hidden by them.

A close-up of the plant's individual spikelets is seen at http://www.backyardnature.net/n/11/111023fo.jpg.

The last picture shows three egg-shaped, or oval, spikelets, with each spikelet bearing maybe a dozen spirally arranged flowers, each flower subtended by and hidden by a pale brown scale. You can also see two slender, wormlike, dark brown items emerging from behind many scales. The wormlike things are pairs of styles arising atop each ovary. Pollen grains land on the styles, germinate, and send their male sex germs down through a pollen tube inside the styles to the ovary. Eventually the fertilized ovary matures into a hard, one-seeded fruit, an achene. Geese and ducks eat these achenes.

The plant in the middle of our road isn't a grass because grass flowers aren't arranged spirally into spikelets like this. Grasses are members of the Grass Family, the Poaceae, but this is completely different, a member of the Sedge Family, the Cyperaceae. One English name for this mostly tropical species is Hurricane-Grass and another is Tropical Fimbry. It's FIMBRISTYLIS CYMOSA, distributed from southern Florida and southern Mexico through Central America and the Caribbean into South America, plus Africa, Asia, Australia, and islands in the Indian and Pacific Ocean.

Since Hurricane-Grass occurs in Florida the species is described in the online Flora of North America. There its habitat is described as "Sands of sea beaches, brackish sandy open sites, often disturbed, commonly just in from mangrove or on sandy road shoulders."

That "just in from mangrove or on sandy road shoulders" couldn't have been more descriptive of where ours grew!

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MANGROVE WATER SEEPING INTO THE OCEAN
At http://www.backyardnature.net/n/11/111023ta.jpg you see the beach here one afternoon this week at low tide something orange-brown seeped from the sand into the ocean's clear water. Apparently it was mangrove water, which is this color nowadays because of its high levels of tannic acid deriving from decaying mangrove stems and leaves.

If it is indeed mangrove water, it's flowing beneath the entire low sand ridge separating the sea from the mangroves. At this seeping-out location, the ridge is maybe 1000 feet across (300m). Several such seeps occur along the beach, but I've noticed them only lately. That makes sense because earlier the water level in the mangroves was lower. Now it's high, and when low tide occurs the mangrove's water level is higher than the sea, so naturally mangrove water would seek release in the ocean.

Marcia tells me that a bit offshore she's seen such stained water gushing up six inches or so above surrounding seawater, so apparently sometimes there are subterranean channels with vigorous flow. That would be less unexpected if we were on limestone where underground rivers often flow in cavern, but here we're on pure sand.

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GARDENING WITH SEAWEED
Each day brings a new crop of wind- and current-dumped seaweed onto our beaches. Some local property owners expect their live-in caretakers to keep their sand yards free of seaweed and everything else, so the daily gathering up this flotsam can be a major chore. Seeing the situation, recent visitor Lorna couldn't suppress her opinion that not using the seaweed was a waste. In Lorna's native Isle of Jersey, off the coast of Normandy, traditionally seaweed was collected and plowed into the soil to enrich it.

When Lorna returned home she sent me a link to a 1966 paper in the journal Agricultural History Review by Brian Blench, called "Seaweed and its Use in Jersey Agriculture," at http://www.bahs.org.uk/14n2a4.pdf.

Among several colorful eye-witness accounts, the paper quotes J. Poingdestre writing in 1682 after a visit to the islands. He reported that "every one of them (had) enough (seaweed) to lay it upon theire grounds as thick as ye spade or plough can turne and cover with conveniency."

Soon after my arrival here on our sand ridge I mixed sand and washed-up seaweed that had lain awhile to have the salt rained off it, and got a mixture in which seeds germinated and plants grew -- until Black Iguanas ate nearly every plant. The few remaining plants grew up stunted and yellowing, displaying classic signs of nutrient deficiency, especially nitrogen. Decomposed seaweed would have provided more available nutrients. I encouraged the staff to pee with me onto the compost heap, for urine has a lot of nitrogen in it, but somehow the practice didn't catch on. I think that urine and livestock manure added to seaweed and properly watered and aerated would compost into a fine, nitrogen-rich growing medium.

Lorna mentions making a nutrient-rich "tea" of seaweed soaked in buckets of water. On the Isle of Jersey, seaweed also was burned to produce potassium-rich ashes for use as fertilizer.

Lacking a good nitrogen source here, maybe our best use of washed-up seaweed would be as mulch during the dry season.

For years Marcia has fed kitchen scraps and seaweed to a certain spot which was never aerated, so that basically things rotted anaerobically. Parts of that pile eventually produced fine potting soil, though it crawls with tiny biting ants.

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PHILOSOPHIZING LIKE GRANDMA MOSES
When I was a kid, Grandma Moses was famous for her colorful, cheerful paintings that broke all rules for showing perspective and other details "real artists" worry about. You can meet Grandma and some of her work at http://gardenofpraise.com/art43.htm.

People might have snickered at Grandma Moses' childlike, untutored technique but Grandma's works touched them in ways other artists' didn't.

I aspire to be the Grandma Moses of Natural Philosophy.

What I mean is that even if I don't have the brains, talent and instruction to philosophize publicly, I'm doing it anyway, for the same reasons Grandma Moses painted: I just feel like doing it, and I believe that what I'm saying ought to be said. Here's one thing I want to say:

Reality is a blossoming, and we're all inside it, both as observers and participants.

Ta-dah! That's my Grandma Moses picture of a white cow standing unconcerned beside a red barn.

*****

Best wishes to all Newsletter readers,

Jim

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