July 10, 2011
Nowadays most folks traveling the beach road slow at the bend so they can see the Black Hawk nest we've been watching since early May. Now the single nestling is growing explosively, dark feathers mostly having replaced the white fuzz. The nestling is fast losing his adolescent awkwardness. He climbs to the nest's edge and for the longest time just gazes out over the scrubby woods below, and the ocean just beyond. You can see him in his favorite viewing position at http://www.backyardnature.net/n/11/110710bh.jpg.
Nowadays at dawn usually towering cumulus clouds rise on the horizon all around, often coming ashore as slate-gray showers that majestically move around us or hit us head-on, and nearly every afternoon massive storms form not far inland, their low thunder rolling across the mangrove as they move away from us.
I can only imagine how this dramatic, ever-changing ceiling affects our bird's mental conception of what the world is like. How would it feel to be that nestling, intuitively knowing that before long he'll be part of that sky, circling and looking down with an acuity of vision and mental fixation we humans can't imagine?
Whatever is going on in the mind of that nestling, until it fledges there's not much more to do than to perch at the nest's edge watching clouds and gazing toward the sea.
ORIOLE GATHERING FIBERS
A yellow and black bird, a kind of oriole, landed on a Coconut Palm frond beside my upstairs porch, as shown at http://www.backyardnature.net/n/11/110710or.jpg.
My vision is poor so often I don't see a picture's details until the image is pulled onto the computer screen. When this new oriole picture appeared, I found I had several things to think about.
First of all, orioles can be hard to figure out because a single species can have different male, female and immature plumages, and even first-year and second-year ones. In this part of Mexico we can expect about eight oriole species and especially the female and immature plumages can look a lot alike. It took a while to figure out that what's in the picture is an immature male Black-cowled Oriole.
Also, our bird is collecting fibers from a Coconut Palm frond. Here Black-cowled Orioles make their pendulous nests from such fibers. You might remember the Black-cowled Oriole nest we posted at http://www.backyardnature.net/n/11/110529or.jpg.
So, what's am immature oriole doing collecting fibers for a nest? Do immatures build practice nests? Do they help their parents, or other pairs of adults with their nests? Or is this immature mature enough to mate? In some bird species these things happen, but I can find no mention of it for this species.
Black-cowled Orioles occur from here to western Panama and just haven't been studied that much. Therefore, we'll just park our picture on the Internet and maybe someday a graduate student studying oriole nesting habits will learn something from it.
INVASION OF SHINY COWBIRDS
In A Guide to the Birds of Mexico and Northern Central America there's an illustration of the Shiny Cowbird, MOLOTHRUS BONARIENSIS, despite the species not being listed as existing in Mexico. Author Steve Howell writes that this South American species that's been introduced into the Caribbean area "is spreading rapidly through much of Caribbean and SE USA and should be sought in places such as Isla Cozumel or Cancún... "
In 1996, just one year after Howell's masterpiece was published, the first positive identification of a Shiny Cowbird in Mexico was made near Celestún on the Yucatán's western coast. Since then the species has been seen in several places, and I'm pretty sure we have them here, too.
Out in the mangroves about a month ago I began noticing black birds singing from snags here and there. At first I thought they were Melodious Blackbirds because of their varied, bubbly, sometimes squeaky calls, though I'd not heard those particular sounds from Melodious Blackbirds around my hut up at Chichén Itzá. I thought that maybe I was hearing a regional accent. On my first visit to New York I didn't recognize the Starlings there because they made such different sounds from those I knew in Kentucky. Also, these black mangrove birds had shorter tails than Melodious Blackbirds, shorter, thicker-based bills, and they were more nervous about being approached.
One day I glimpsed a modest glimmer of bluishness as one of the mangrove birds flew from his perch, and that was when I started thinking "Shiny Cowbird," which Howell describes as having glossy, blue-black wings and tail.
They're nervous birds and I haven't been able to get good pictures. I did make a brief video from a distance, of a singing bird, which I'm keeping just as a voucher in case a future researcher needs it. You can see a bird's profile and flight silhouette at http://www.backyardnature.net/n/11/110710sh.jpg.
In the larger image can you see the hint of blueness that's so distinctive of the Shiny Cowbird? The thick-based beak arising so high on the forehead is very cowbirdy. The Bronzed or Red-eyed Cowbird also is found here, but it lacks the bluishness, is more thick-necked, has a thicker beak and raises its neck ruff.
The Shiny Cowbird's presence in this part of the world is nothing to celebrate because the birds are nest parasites -- females lay their eggs in the nests of other species, at the expense of the other species' nestlings. Already Shiny Cowbirds are suspected in the decline of several Caribbean bird species, including Puerto Rico's critically endangered Yellow-shouldered Blackbird.
ECOSYSTEM UNDER STRESS
So, lately we've seen Lethal Yellowing Disease killing about 90% of the region's Coconut Palms. Washed up on the beach we've found lots of Green Bubble Alga, known to overgrow and smother coral reefs. We've found dead and dying Long-spined Sea Urchins who have just experienced an epidemic killing over 90% of the Caribbean's population. And now in this area's mangroves nest-parasitic Shiny Cowbirds are appearing in fair numbers resulting in greater stress on the area's nesting birds.
More and more I get the impression that even in this wild, isolated place plants and animals are suffering from a spectrum of environmental stress.
CRAB IN A WORM SHELL
We've already met Caribbean Hermit Crabs, which move across the sand carrying various kinds of abandoned seashells into which they withdraw when they feel threatened. You can see one peering from his shell at http://www.backyardnature.net/yucatan/hermit.htm.
The other day I came across a crab carrying not the usual snail shell but rather the long, coiled shell of a so-called worm or sea snail, genus Vermicularia. That was so unusual that I picked up the crab and shell for a better look. Shortly the crab surprised me by removing most of his body from the shell as he tried to pull the shell loose from my fingers. This gave me a good view of the crab's long body, which nearly always is hidden inside a shell, as shown at http://www.backyardnature.net/n/11/110710cc.jpg.
This long body cues us to the fact that hermit crabs are not "true crabs," which normally possess rounded, oval or square, and often flattened bodies. In fact, hermit crabs are more closely related to certain kinds of lobsters than to true crabs.
LONGHORNED BEETLES WITH REALLY LONG HORNS
Here during the early rainy season biting flies and mosquitoes are out in force, so regularly the tourist area is fogged with organically based, biodegradable, pyrethrum-based insecticides. Of course many insects other than biting flies and mosquitoes are killed. Among the most conspicuous found lying back-up on the ground these days are longhorned beetles like the one at http://www.backyardnature.net/n/11/110710el.jpg.
A close-up of the head area showing black, many-faceted compound eyes above the antennae and surprising facial hairiness can be seen at http://www.backyardnature.net/n/11/110710em.jpg.
Longhorned beetles are members of the Longhorn Beetle Family, the Cerambycidae, of which about 20,000 species are described. The horns in the name refer to the very long antennae species in the family usually have, and our pyrethrum-killed species is one with especially long antennae. Volunteer identifier Bea in Ontario thinks we may have a member of the genus Eburia.
Whatever the species, longhorned beetles typically produce larvae that bore into wood, either living or dead. Some species do serious damage to wood buildings, one having earned the common name of Old-house Borer. Asian Longhorned Beetles, now introduced into the US and Europe, pose a big threat to healthy living trees, both in natural and suburban areas.
HOW PYRETHRUM WORKS
Pyrethrum is an extract from the flower heads of certain Chrysanthemum species. It affects the nervous system.
Animal functions such as movement and feeling are possible only as long as weak electrical impulses move through the body. They pass from nerve to nerve by way of "sodium channels," which function by conducting sodium ions (Na+) through cell plasma membranes. Wikipedia's illustrated page explaining the process is at http://en.wikipedia.org/wiki/Sodium_channel.
So, nerves do their jobs only as long as sodium ions can travel from nerve to nerve.
Pyrethrum -- or more correctly the six chemical compounds known as pyrethrins that are the active ingredients of pyrethrum -- bind to the sodium channels, "clogging them up." The result for the insect is a shut-down nervous system. The insect can't move, can't breathe, and can't do a lot of other things, either, so it dies.
Human nerves also have sodium channels, so is pyrethrum safe for humans?
The general wisdom is that in concentrations humans experience when using pyrethrum-based insecticides, or being where such insecticides have been used, no danger is involved.
However, pyrethrum is extremely toxic to fish such as Bluegills and lake trout, and moderately toxic to birds such as Mallards and Bobwhites, and of course it's lethal to many beneficial insects such as honeybees and flower-pollinating wasps.
Mammals are less affected because pyrethrins are easily metabolized and don't accumulate in the body. They break down in sunlight and are unlikely to concentrate in the food chain.
Still, it's good to remember that we living things are all related, and that we share many, many chemical processes that keep us going. If pyrethrum kills insects by clogging up sodium channels, a good guess is that it at least impacts in some small way the sodium channels of the human nervous system. In fact, among humans sometimes pyrethrum does produce skin irritation, itching, pricking and local burning sensations. At least one report describes more serious chronic effects, including circulatory and hormonal effects.
SACRED MAYA FLOWER
Below I describe a bike ride taken last Sunday. During that ride the road brought me close to several ponds and lakes. Among the most eye-catching plants at one of the ponds was the white-flowered waterlily shown at http://www.backyardnature.net/n/11/110710li.jpg.
In that picture, the leafless tangle in the background consists of branching aerial roots of the Red Mangrove. The open water is completely surrounded by Red Mangrove, which apparently finds the water lilies' water a little too deep. I couldn't get close enough to the lilies for a good picture but a couple of flowers floated near enough to reveal field marks enabling their identification. Notice the crinkled leaf margins and -- barely visible -- lines of tiny black spots on the flowers' greenish sepals at http://www.backyardnature.net/n/11/110710lj.jpg.
In the literature English names given for this species include Dotleaf Waterlily, White Water Lily and White Lotus. It's NYMPHAEA AMPLA.
And that interested me greatly, for back in the 1970s for a couple of dry seasons I served as naturalist for the Foundation for Latin American Anthropological Research, FLAAR, based in Guatemala City, Guatemala. We specialized in taking tourists with special interest in Maya archeology to very hard-to-reach Maya ruins deep in the rainforest of northern Guatemala and Chiapas, Mexico, and on those trips we always were on the lookout for water lilies.
That's because the archeologist leading the tours had theories about ancient Maya shamanistic use of water lily flowers. And the water lily in question was our Nymphaea ampla. If you Google the keywords "sacred Maya flower" the first return should be a PDF document published by my former boss, Nicholas Hellmuth, entitled Sacred Maya Flower.
In that document you can see how Maya iconography apparently represents Nymphaea ampla in various religious contexts, the water lily occupying the zone between the Maya netherworld, under the water, and the world of humans beyond the water. Sometimes the water lily motif sprouts from the head of people portrayed in Maya art, maybe even with a fish in mid-air nibbling on the water lily. This, maybe, represents a shaman in contact with the spirit world, through the agency of the water lily, which may be mildly hallucinogenic.
Whatever the deal, last Sunday it was good to see lots of Nymphaea ampla in a little pond nearby. The species is very sensitive to environmental changes, having disappeared in many areas where the water became stirred up or polluted.
Nymphaea ampla is found from Texas south through Mexico, the West Indies and Central America into South America.
A BIKE RIDE
It's mid afternoon and a narrow lane of white sand and gravel leads south along the beach. Heavy sunlight, the gritty sound of bike tires on hard-packed gravel, glare and heat, the wind and I flowing southward at the same pace so I don't feel this wind, just see it making waves and shaking grassblades and leaves, a moving, invisible thing that touches, like music, like me.
On the left there's blue ocean, sand and washed-up-trash, on the right, wild mangrove and, all down the coast, gringo winter homes, patches of strand scrub with Seagrapes and Beach Lavender, little coconut plantations, scalped or weedy real-estate lots, Mexican ranchos and fisherman shacks, and on the road there's the sense of going for the going, not for getting anywhere, and I'm glad I'm the one in that mental groove, glad to be a self-improvising theme in Mexican afternoon beach jazz.
Double-bass thunder rumbles behind me but I've already seen the big cloud with its dark bottom. It's passing to the north, though, so my eyes stay fixed ahead, not going to undo this mood, and I like the idea of storms moving around me as I navigate where I've never biked before, and maybe it'd feel good to get wet.
Waves splash not twenty feet away, nervous little curls of dusty, coolish breezes stir, electricity in the air, good how the body and bike just keep going, snare drum wave-splash clickity-click chain on gears.
It gets darker and lightning strikes close, flash and thunder sforzando disharmonious with gauzy, glossy gliding-with-the-wind-red-1965-Chevy-convertible feeling. But, keep it simple, eyes straight in front, bluesy saxophone in my head, the thunder stops and it doesn't even start to rain.
I'm biking a big circle so an hour or two later I'm headed back north chasing the big storm that's been acting up behind me. Now it's bruised blue, silent and spent. Now there's a headwind and I'm sweating hard, skin flushed red and hot, in the air pin-pricks of icy drizzle all that's left of the storm, big old brassy easy-gliding trombone dying away amidst teeny little piccolo chirps.
Here it's been raining hard, odor of wetted dust and alternating pools of hot fog and dead chill, glasses fogging up, quickly clearing then fogging again, vegetation fresh-washed glossy green, birds and their after-the-rain calls and for awhile I rest beside a pond held in sepulchral chill dumbly staring at white waterlily flowers so perfectly formed and brightly gorgeous my mind can't digest them, can't right now admit such frozen elegance into my personal little storm of sweaty forward movement, something like a lonely strain of Debussy in a John Coltrane set that's gotten turned into a Sousa march.
Back at Marcia's, it's been a real downpour, and I missed the whole thing, saxophone, sweat and waterlilies.
Best wishes to all Newsletter readers,