| Vol. 17 No. 21 |
Final
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Missing
Song Birds
Welcome Guests Soon Fly Far Away
By Edward Davidian, Staff Writer
The Clovis Free Press
CLOVIS -- The familiar songbirds
that build their nests in our yards and trees and meadows are the
most watched, and probably the most beloved of all wild creatures.
They are also among the most traveled, and therefore shared, for most
of them spend their allotted years shuttling back and forth between
their summer and winter homes, often following long-established flight
paths that take them over thousands of miles of land and water.
The migratory songbirds found in North America
include roughly 350 species, of which about 250, known as Neotropical
migrants, spend their winters in the New World tropics of
southern Mexico, Central and South America, and the West Indies. The
other 100 species, called short-distance migrants, winter
chiefly in the southern U.S., particularly along the Gulf Coast. Migratory
songbirds can be found in virtually every habitat on the continent,
and usually half or more of the breeding birds in any sampled area
are migratory. In some northern forests, for example, less than 10
percent of the songbirds present in the summer remain throughout the
year: the rest winter in places far away.
Migratory songbirds play a major role in
the health and functioning of ecosystems, as consumers of insects
(especially those that defoliate trees), dispersers of seeds, and
pollinators of flowers. They are also of considerable value to regional
economies. When forest birds eat insects, the result is greater tree
growth and a longer period between insect outbreaks -- services that
may be worth as much as $5000 per year for each square mile of forest
land. Millions of people watch birds as a hobby and many of them flock
to areas where birds concentrate, where they spend millions of dollars
on ecotourism.
In the spring of the year, mostly from March
through May, migrants abandon their wintering grounds, fly northward
in the dark of night over several thousand miles, and spread out over
the North American continent, where the warming weather and the emergence
of new leaves provides vast quantities of insects. When summer ends
and autumn comes, the declining supply of insects drives them south
again. The nonmigratory species that remain are limited by harsh winters
and food that is much harder to find.
To live in both the temperate and tropical
worlds and to find sufficient food during their long and often intercontinental
flights, migrants must be flexible opportunists. Some territorial
species that consume nothing but insects during the breeding season,
such as orioles and kingbirds, are in winter -- where most of us never
see them -- gregarious consumers of fruit and nectar. In the twice-a-
year transformation they switch from carnivores to vegetarians.
Such adaptability should place migratory songbirds
among the least vulnerable of all animals to the major changes in
land-use and wildlife habitat that accompany human activities. To
some degree this seems to be the case, for most of them have global
populations that are estimated in the millions or tens of millions.
Some especially abundant species, such as the Red-eyed Vireo and Blackpoll
Warbler, may number in the hundreds of millions.
During the Spring and Fall migratory periods,
migrants concentrate in huge numbers in tree-covered Clovis City parks
where, for a few weeks, the diversity of birds can rival that found
in tropical forests. It is in part this spectacle of abundance, plus
their phenomenal ability to navigate at night -- using the stars and
the Earth's magnetic field -- that makes migratory songbirds so intriguing
to bird watchers and the public at large. Watching large flocks of
dozens of species of migratory songbirds pass through the backyard
of my own home in Clovis solidified my own lifelong interest in birds
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