Biology Reference
In-Depth Information
treefalls that are quickly shaded out, may be short-lived or unpredictable. Consequently, few
of a tree's seeds may germinate or survive past the seedling stage. Yet trees that have evolved
to live hundreds of years and produce 10,000 seeds per year have their own built-in protec-
tion for persistence. The production of viable offspring can afford to wait for the favorable
but infrequent germination conditions that may depend on a fire, windstorm, or other event.
After all, to be successful—to pass on its genes to the next generation—an individual need
only replace itself once in a hundred years, and canopy trees live to be much older than that.
The life history of a rare tropical canopy tree is a study in patience.
These hypotheses proposed to explain patterns of rarity in tropical trees are not mutually
exclusive, and all are likely to be part of the answer. And, most interestingly, none is designed
to explain how the large number of species was generated in the first place. That piece of the
puzzle remains unsolved.
On a tranquil morning seven days after arriving in Madre de Dios, George, Sue, and I started
back up the Tambopata. A heavy mist on the river kept the kingfishers grounded, but the
sound of the outboard engine stirred awake slumbering capybaras on the floodplain islands
as we approached. The world's largest rodents had found a safe haven from jaguars in the
middle of the channels. There was not much green on the sand and stone beaches for their
breakfast, but there were no big cats or anacondas, either.
After a night's rest, we continued our journey upriver before dawn, making our way to a
blind created by some washed-up trees on a floodplain island. Across the channel an exposed
clay cliff, about ten meters high, appeared before us like a vast canvas painted in a dull ocher
wash, lifeless. “Just wait,” Sue whispered. “You won't believe this.”
With the first warming rays of the sun, flashes of blue, yellow, and gold flitted along
the cliff face, followed by red and green with dashes of scarlet, blue, and chestnut. The
collpa
, or mineral lick, was alive with macaws and parrots, squawking and chewing on the
mineral-rich earth. Not a handful of birds but hundreds of them represented five species
of macaws—scarlet, red-and-green, blue-and-yellow, chestnut-fronted, and red-bellied—and
at least nine species of parrots. We counted blue-headed, mealy, yellow-crowned, orange-
cheeked, and white-bellied parrots, as well as dusky-headed, cobalt-winged, and white-eyed
parakeets and, rarest of all, an albino blue-headed parrot. This must have been one of the
densest concentrations of natural color anywhere. The macaws and parrots are believed to eat
the earth to obtain sodium—an element in short supply in the food they normally ingest—and
perhaps to help detoxify some of the chemically laced seeds they consume. There may also
be social functions to this gathering. Whatever the causes, in this Kingdom of Rarities, the
