Sunday, October 18, 2009

St. Thomas

Wednesday April 8 found us anchored off St. Thomas in the British Virgin Islands. St. Thomas, unlike Grand Turk but like Puerto Rico, is a high island, but one that is not high enough to capture and hold the trade winds that bring rain to Puerto Rico. As a result, St. Thomas (like the other Virgin Islands) is covered in dry scrub. There are no endemic birds here.

Pearly-eyed Thrashers (Margarops fuscatus) penetrate right into the town of Charlotte Amalie; this one was singing in a suburban garden.

After a stroll through Charlotte Amalie, Eileen and I decided to take a minibus tour around the island. This gave us a chance to see the native vegetation. the picture above gives you a pretty good idea of what it looks like: the trees are short and scraggly, and with water loss a real problem their leaves are quite small. The large leaves of the ground vegetation are stiff and thick (and often sharp-pointed, spiky and otherwise miserable to walk through), and may reduce water loss with waxy, more or less waterproof coatings.

Closer looks at a few roadside plants (note the smallish leaves on the upper photo -- the technical term for this is microphyllous, which simply means "small-leaved").

Seagrape (Coccoloba uvifera) is a common coastal tree everywhere in the Caribbean. What's more, its broad, thick leaves make it easy to identify. It is extremely salt-tolerant, withstanding both salty soil and sea spray with ease. Its fruits, when ripe, do look a lot like concord grapes (and are used to make jam), but the plant belongs to the buckwheat family (Polygonaceae), so it is a grape only in name.

Green Iguanas (Iguana iguana), an introduced species, are everywhere in the countryside. At almost any place we stopped in roadside scrub, a bit if peering into the brush would turn up an iguana or two, ranging from bright green babies to hulking moss-grey adults.

We didn't see a lot of birds on our drive around the island -- and the birds we did see, or hear, almost always turned out to be Bananaquits (Coereba flaveola). Being common, though, doesn't make Bananaquits any less fascinating.

Why are these birds so phenomenally successful, particularly in the West Indies (they range from Mexico to Argentina)? Why is there only one species (though in a number of subspecies) across its huge range (a point I'll raise again in my next entry)? And just what are Bananaquits in the first place? The species is currently placed in a family of its own, the Coerebidae, and its relationships -- which surely lie somewhere in the tanager/warbler/American finch assemblage, but given that assemblage's vast size this isn't saying much -- are still an open question.

Dry, scrubby, and, perhaps, not as biodiverse as a greedy naturalist might wish (at least on land), St. Thomas still has its beauties. I'm glad to have seen it.