March 7, 2010

YELLOW-FACED GRASSQUIT
A neat thing about the tropics is that, just when you think you've seen all the local species, something new comes along. Species diversity in the tropics is simply much greater than in the Temperate Zone.

So, early one morning this week on my way to the bar (that's where the wireless signal is strongest) I wasn't surprised when the first Yellow-faced Grassquit, TIARIS OLIVACEA, I've seen on Hacienda Chichen's grounds flitted from the lawn grass onto a spiny-tipped blade of an ornamental agave, as seen at https://www.backyardnature.net/n/10/100307gq.jpg.

Yellow-faced Grassquits, despite seldom coming onto the grounds, are fairly common in the Yucatán in weeds along roadsides and in abandoned fields. This bird must have been just wandering through. He stayed four or five days, then drifted on.

The orangish-yellow eyebrow, or supercilium, throat and partial eyering just below the eye (the subocular crescent, as Howell calls it) along with the thick, stubby beak make Yellow-faced Grassquits easy to identify. There's just nothing else like it. An important field mark not seen in the above back-shot is the black chest beneath the yellow throat.

You might guess that with such a short, stout beak Yellow-faced Grassquits are classified in the same large subfamily, the Emberizinae, as sparrows, towhees and the like, and that's true. The species occurs from eastern Mexico and the Greater Antilles to northwestern Venezuela.

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GUAVA-EATING SALTATORS
Next to Hacienda Chichen's office entrance a Guava tree is producing ripe guavas, which many birds love, especially the Black-headed Saltators, SALTATOR ATRICEPS. When I sat on the steps to wait for someone it wasn't five minutes before the saltators' passion for guavas overcame their nervousness about visiting the tree only about ten feet from me. You can see one of the birds, his throat feathers wet from ripe guava, at https://www.backyardnature.net/n/10/100307sa.jpg.

A saltator would gorge himself about half a minute, then another would fly onto a branch nearby, and complain loudly with sharp, squeaky sounds a little like a wet hand rubbing a wet balloon, CHEUK! CHEUK! CHEUK! Before long the visitor couldn't stand it any longer, would hop down and drive the other away, and then before long yet another would come with the same calls and finally displace the eater after he'd gorged awhile.

Howell in his A Guide to the Birds of Mexico and Northern Central America describes saltators as a group as "fairly plain tropical grosbeaks of forest edge and second growth." With its short, thick bill you know that it must be in the same family as sparrows, towhees and grassquits. However, being larger birds and with more massive bills, they're in a different subfamily, the Cardinalinae.

Black-headed Saltators are fairly common residents from central eastern Mexico to Panama.

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SALTATOR IMMATURE PLUMAGES
Once the above picture of the Black-headed Saltator was on my screen I got the impression that we had a youngish bird not quite yet with a fully developed adult plumage. The black rim around the bird's white throat as well as the black face weren't black and sharply defined enough, and the white eye stripe wasn't bold and well defined enough. Also, there was a hint of the stripe passing well beyond the eye. That latter detail made me call up the photo at https://www.backyardnature.net/n/09/091213sa.jpg.

That photo, taken two months ago, struck me then as probably an immature Grayish Saltator because the eye stripe, or supercilium, passed way beyond the eye instead of curling around the eye's top as a Black- headed Saltator's does. However, I had my doubts about it being a Grayish because of the hint of a black rim around the white throat, which Grayish Saltators aren't supposed to have. Now I'm thinking that instead of an immature Grayish it may have been an immature Black-headed Saltator.

Here we're dealing with issues that aren't made clear in generally available sources. I'm tickled to contribute these field notes for others also struggling to master such issues as the saltators' various immature plumages. Now when anyone Googles the keywords "saltator immature plumages" they'll find this link near the top of their page.

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NOPAL CACTUS IN FLOWER
Mexico is home to the greatest diversity of cactus species in the whole world, and the Yucatán has several species found nowhere else. However, the Yucatán's rarest and most interesting cacti cluster along the northwestern coast, which is the most arid part of the peninsula, not here in the central Yucatán. The plant list for the adjoining state of Quintana Roo lists fourteen cactus species for that state and I suspect that Yucatán state hosts a similar number.

One of the most common cacti around Hacienda Chichen one that thrives in thick scrub surrounded by small, leafy trees. You can see our species struggling for space in a leafless, dry-season thicket at https://www.backyardnature.net/n/10/100307op.jpg.

Cactus naming can be hard, maybe because the taxonomists who work on plants just don't like dealing with big cactus pads that are so hard to dry and, especialy, don't like the spines. I think our cactus is NOPALEA COCENILLIFERA, the Cochineal Nopal Cactus. I say "think" because normally you think of the Cochineal Nopal Cactus as being spineless or almost so, and you can see that this one has at least a few small spines at https://www.backyardnature.net/n/10/100307oq.jpg.

And the woody trunk is even spinier, as seen https://www.backyardnature.net/n/10/100307on.jpg.

The trunk rises three or four feet before abruptly sprouting green pads. The online Flora of North America says that usually it's spineless, but especially on older pads can have up to three spines. On our plant's trunk some of the spine bunches have more than three spines.

The Flora also says that "This species may have been selected for spinelessness in Mexico, much like Opuntia ficus-indica, to ease the culturing and collection of cochineal scale insects for red dye." That implies that wilder stock was spinier, and here we are in the home of the wild stock, so why shouldn't our plants be spinier than the spineless ones introduced into other parts of the world?

The quote given above speaks of a red dye, and that derives from tiny insect larvae who feed on this and other closely related cacti. It's an interesting subject and you might want to check out the Wikipedia page on the dy cochineal at http://en.wikipedia.org/wiki/Cochineal.

This cactus also produces the edible pads that in Mexico are eaten in large amounts once the pads are completely de-spined. This is a very important cactus species.

I like to think that the plants around my hut are descendents of plants the builders of Chichén Itzá took good care of, and over the centuries selected for planting those who had the least spines, until today they are practically spineless, but not quite, at least not on the ones here.

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CACTUS LEAVES & AREOLES
A pricklypear's beavertail-shaped pads are stem joints, not leaves. However, most cacti do have leaves, though usually they're tiny and soon fall off. A leaf on a pad rim of Opuntia inaperta can be seen at https://www.backyardnature.net/n/10/100307oo.jpg.

In that picture the down-curved, green thing, which is about ¼-inch long (7 mm), is the leaf. The white thing is a spine, and the several much smaller, almost transparent spines at the base of the single large, white spine are "glochids," If you've ever poked a cactus, succeeded in avoiding the spines, but ended up pulling almost-microscopic stickers from your finger anyway, those were the glochids. Usually glochids give cactus lovers more grief than spines.

Flowers, fruits, leaves, spines and glochids don't just erupt from any random part of a cactus's pads. Over the cactus's body there are specific small zones, called areoles, where those things arise. In the above photo you're looking at an areole from the side. From above it would be more or less circular.

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ALOE VERA FLOWERING
Probably most of you have at one time or another kept a pot of Aloe Vera in your home (Aloe Vera is both the common and scientific name). However, I'll bet that few of your plants every flowered. Here in the land of no frost they're prettily flowering now, as you can at https://www.backyardnature.net/n/10/100307al.jpg.

The above plant, growing up against a hot, south-facing hotel wall in Pisté, has succulent blades about knee high and flower clusters some four feet high. You can see some bees busily visiting the drooping flowers at https://www.backyardnature.net/n/10/100307am.jpg.

A longitudinal section of a flower showing six stamens of slightly differing lengths and an oval, small ovary, the future fruit, nestled at the base of the stamens at the picture's bottom left, is shown at https://www.backyardnature.net/n/10/100307an.jpg.

At the far right in that picture you might notice how the stamens' brown, baglike, pollen-producing anthers are attached to their yellowish, matchstick-like filaments at their backs so that the anthers can seesaw back and forth and swivel. Such back-attached anthers are said to be "versatile." When identifying flowering plants often it's important to notice how anthers are attached because the manner of attachment is fairly consistent within groups of plants. Many anthers are attached to the filament at their bottoms, and thus are "basifixed."

Anyway, this is the Aloe Vera of commerce, famous as a skin moisturizer, a shampoo base, an ingredient for laxatives and as a digestive aid, and many other purposes. Most of the world's supply is grown in southern Texas and adjacent northwestern Mexico and the West Indies. Supposedly it's native to islands in the Atlantic. It's often cultivated outdoors in the southwestern United States, where it occasionally escapes. I like to keep a plant in case I get burned. Smear some Aloe Vera juice over a burn and it doesn't form blisters as readily as otherwise.

The Flora of North America assigns Aloe Vera to its own family, the Aloaceae, but other sources place it elsewhere. In school I learned it was in the Lily Family, but at Wikipedia it's put into the Asphodelaceae, which I've never heard of.

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A BIG-FRUITED ORCHID
Nowadays it's not unusual to see what's shown at https://www.backyardnature.net/n/10/100307or.jpg.

That's an orchid growing about 20 feet up on a big branch of a Piich tree (Enterlobium cyclocarpum), which now in the dry season is almost leafless, inviting brilliant sunlight to illuminate the orchid's unusually large (for an orchid), broad, several-veined leaves. This particular orchid is bearing an uncommonly large, several-veined, fruit on its sagging, 16-inch (40 cm) peduncle. Though many such orchids occupy larger trees here, few bear such fruits.

In a land with no field guides to help identify the orchids and no identification keys available to the general public, how do you get the name for something like this?

I knew the plant family it belongs to -- the Orchid Family -- so I went to "The Flora of Quintana Roo" (Quintana Roo being the state just east of us), and found 24 species listed there in the Orchid Family. Then I set using the Google Image Search Engine, searching on each species name.

By comparing pictures found there I'm fairly sure that our orchid is CATASETUM INTEGERRIMUM, described as occurring from Mexico to Nicaragua, and as growing in humid forests, coffee plantations and open country. I find no English name for it.

Nearly all photos of this species on the Internet show the plants' exceptionally large, strange and beautiful, yellow and green flowers, which I assume will appear during the rainy season.

From what the pictures show, this will be an event worth waiting for.

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MAIDEN FERN ON THE CISTERN
So far at Hacienda Chichen I've found only a single population of Roughhairy Maiden Fern, THELYPTERIS HISPIDULA. It lives in dense shade on the mossy, water-saturated, limestone-rock walls of an old cistern supplying water to the gardens. You can see it at https://www.backyardnature.net/n/10/100307th.jpg.

These are robust ferns with fronds averaging over three to four feet long (1-1.3 m). If you were with me this time last year in the woods near Natchez, Mississippi, you might remember our seeing the Southern Shield-Fern, Thelypteris kunthii, still shown at https://www.backyardnature.net/n/h/shield-f.htm.

These two species belong to the same genus, and are closely related within the genus. One of the most conspicuous features separating them is that our Roughhairy species is -- rough and hairy, as shown at https://www.backyardnature.net/n/10/100307ti.jpg.

In that picture the dark, spherical items are the "fruit dots" or sori. Each sorus consists of many sporangia, which are the blackish, spherical little things in clusters in the picture. Inside each sporangium many spores are formed. Clearly, then, spores are very small. You can get an idea of how many spores must be produced from the fern's very many sporangia by looking at a small section of one frond at https://www.backyardnature.net/n/10/100307tm.jpg.

In the center of each sorus there's what looks like a more or less circular piece of brown paper. That's what remains of the indusium, which is the cellophane-like covering found on many sori. In the picture it looks like the indusia are attached at their centers, thus constitution the top part of an umbrella-shaped structure. Actually indusia in the genus Thelypteris are C-shaped, but often with the ends of the C almost touching, so that at first glance they can look like Os. Thelypteris's C-shaped indusia are attached to the frond along their sides. These seemingly unimportant details are very important to nail down when identifying ferns. You can see a Roughhairy Maiden Fern's frond with freshly developed indusia covering immature sori, better showing their C-shaped nature, at https://www.backyardnature.net/n/10/100307tl.jpg.

Roughhairy Maiden Ferns occur in the southeastern US, Mexico and the West Indies south through tropical South America, plus tropical Africa, Australia and southern Asia. The species is divided into four subspecies, and ours is not the same subspecies as in the US. One feature worth noting of our plants is that the fronds arise from exceptionally thick stems that creep along the cistern's mossy surface, as shown at https://www.backyardnature.net/n/10/100307tk.jpg.

That stem is about 15 mm thick, over half an inch.

The Flora of North America describes its habitat as "Woodlands and limestone sinks, especially in seepage areas and along streams." That doesn't mention cistern walls, but with our cistern walls composed of cemented limestone rocks long saturated with water, I'd say that the fern must feel at home here, anyway.

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FERN PROTHALLI
Our Roughhairy Maiden Ferns are so at home on our deeply shaded, mossy, water-saturated cistern walls that below the fronds it's easy to find prothalli, which is a little unusual. You can see a good one at https://www.backyardnature.net/n/10/100307tg.jpg.

In the picture, the prothallus is the roundish item at the picture's left, with a surface texture somewhat like that of a liver. Only one cell thick, the structure is some 5 mm across (1/5-inch).

Prothalli, which are capable of photosynthesizing their own food and are free living plants, are features of every fern's life history. To understand them, let's start with a green, wall-hanging frond like one of those shown above, whose multitudinous sporangia release innumerable spores into the air.

When a frond-produced spore lands somewhere, if the environment is just right, it does NOT, like a seed, sprout something that turns into a plant like the one that produced the spore. What issues from the spore turns into a prothallus. Most prothalli are more or less heart- or kidney-shaped like the one in our picture.

From prothalli arise tiny, spherical structures called "antheridia," which produce male sperm, and tiny, flask-shaped "archegonia," which produce female eggs. Often both antheridia and archegonia occur on the same prothallus.

When a sperm fertilizes the egg, then the egg does sprout rather like a germinating seed, in the sense that what the sprout turns into is the big thing we think of as the fern. In the above photo you can see a parsley-leaf-like blade emerging from inside the prothallus' sinus or indentation. That's the sprout we're talking about. Once the sprout is self sustainable, the prothallus disintegrates and the sprout grows into what we think of as a fern.

So, we have two very different forms of free-living, photosynthesizing plants alternating with one another during the life cycle of every fern. In biology class this phenomenon is referred to as "alternation of generations," and when it all sinks in, it's mind- boggling. It's almost like a dog and a snail alternating with one another in one life, with snails (like prothalli) having sex to produce dogs, but the dogs (like spore-producing fronds) walking around occasionally budding off spores, from which snails emerge.

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IDENTIFYING TROPICAL AMERICAN FERNS
A new resource has appeared on the Internet that works pretty well, and is fun to use. It's an interactive key to the genera of Tropical American Ferns. If you can identify a fern to genus level, you're halfway home.

At http://www.plantsystematics.org/ click on "Diagnostic Keys" then on the resulting new page entitled "Plant Keys" hit "Neotropical Fern Genera."

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SENSES
Browsing my daily-updated RSS news feeds from various sources dealing with Nature -- that page is at https://www.backyardnature.net/i-rss.htm -- I noticed a trend: Several new studies reported on new insights into various animal species' senses.

I read about ants navigating with "stereo smell" and fish who recognize other fish faces based on UV patterns. Honeybees find their way using polarized UV light and a study found that, while humans have 10,000 taste buds, catfish have ten times that many. This prompted me to look for more information about animals with amazing senses. One good website was at http://faculty.washington.edu/chudler/amaze.html.

What I read ignited two main trains of thought. First, my conviction was reinforced that all animals sense a complex and enriching environment around them. As such, animals deserve to be regarded as much more aware, vital and worthy of living their own lives than we grant them.

The second thought arose from the first: Humans are animals, too, so it's also worth reflecting on our own beautifully crafted set of senses.

One way to see our human senses is that they are exquisitely fine-tuned to enable us survive in the frightfully thin and fragile film of life coating the third planet from the Sun, which is a mediocre star in an unexceptional galaxy, which is one galaxy among billions, located in a rather unremarkable corner of the Universe. Putting our package of senses in that context, it's worth noting that just beyond teeny Earth's modest film of life there's no other place in the known Universe where our particular mix of senses is appropriate -- where we can even survive.

If we were on a spaceship in dead space and alarm bells went off, our senses would alert us to the fact that we need to figure out what's happening, and take action.

In the context of the Universe, our spaceship is Earth, and, indeed, our senses are telling us that the proper response to what's going on today is education, and getting involved.

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Best wishes to all Newsletter readers,

Jim