Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: SATURDAY, February 20, 1993 TAG: 9302200093
SECTION: CURRENT PAGE: NRV-2 EDITION: NEW RIVER VALLEY
SOURCE: STEVE KARK
DATELINE: LENGTH: Medium
BE ON LOOKOUT FOR RAIN-FOREST VISITOR
There is a bird that spends much of the year in the tropical rain forests of South America in the dense, leafy canopy that rises a 100 feet or more above the forest floor.There, it is not a remarkable bird. Its olive-drab color would make it hard to spot in the abundance of the rain forest among more exotic birds, including colorful macaws and large-beaked toucans.
What does this have to do with us in the New River Valley? you might ask.
Well, that dull green bird lives here part of the year.
Some time soon - it may already be happening - the bird will begin its long migration north to its breeding grounds, which include much of the Eastern United States.
At some point during its journey, the male of the species will molt and acquire the scarlet red body and black wings that make the scarlet tanager more familiar to us.
In contrast to its inconspicuous coloring in the tropics, the tanager's brilliant color during breeding makes it a memorable visitor to our forests. While it rarely visits feeders, the tanager is a striking sight against the background of our own springtime foliage.
No one knows for sure what triggers the tanager's return each spring, although researchers have offered several possibilities.
Jerry Via, an ornithologist at Virginia Tech, tells me that some have suggested it could be an internal mechanism, like a biological clock. Or, it might be triggered by the length of the day. Even at the equator, he says, there is a seasonal change - however imperceptible it might be to us - in the amount of daylight each day.
The bird travels only at night, stopping each day to restore the energy it had burned in flight. Night flights are cooler, too; it takes less energy to fly a longer distance.
Again, researchers have studied how the bird finds its way in the dark. Studies show the tanager actually guides itself by the stars. Migrating birds were put inside something like a planetarium and it was found that they always oriented themselves toward the North Star, Via says.
It is remarkable, don't you think? Imagine a night sky filled with the ghostly migrations of birds silently making their way north beneath the moon and stars. One has to be a little staggered by the beauty of it all.
I'll leave the porch light on.
Steve Kark is an instructor at Virginia Tech and a correspondent for the Roanoke Times & World-News. He writes from his home in scenic Rye Hollow, in a remote part of Giles County south of Pearisburg.