Climate Change and El Niņo a Threat to Songbirds, Study Says
June 15, 2000
WASHINGTON (AP) -- Climate change and a possible increase in El
Niņo events could seriously reduce the population of songbirds in
North American forests, a study suggests.
Researchers at Dartmouth College and Tulane University analyzed
the effect of natural climate cycles on the black-throated
warbler and found that the migratory songbird did poorly in years
when there was an El Niņo cycle.
Dartmouth researcher T. Scott Sillett, first author of a study
appearing Friday in the journal Science, said that El Niņo
climate cycles reduce the insect and caterpillar food supply for
the warblers at both the bird's breeding grounds in New Hampshire
and their winter home in Jamaica.
As a result, the small bird produces fewer young during the El
Niņo years. Conversely, during the La Niņa years, the bird has
more to eat and has better success in raising young, the
researchers found.
El Niņo refers to a warming of the usually chilled waters of the
Pacific Ocean off the western coast of South America. The effect
extends westward and causes a worldwide change in temperature and
rainfall patterns.
La Niņa has the opposite thermal effect, with some Pacific
Currents becoming colder than normal. This, too, affects
worldwide weather.
Sillett said there is concern that global warming, a general
trend toward warmer temperatures worldwide, will increase the
frequency of El Niņo climate cycles. This could be very bad news,
he said, for the warbler and other such small forest songbirds.
"If the El Niņo cycle becomes stronger, it could increase the
chances of having years when warbler survival and reproduction
rates reach extreme lows, perhaps even approaching zero," said
Sillett in a statement. He said strong El Niņo cycles could
"elevate the risk of extinction" for such birds.
Bernt-Erik Saether of the Norwegian University for Science and
Technology wrote in Science that a "frightening consequence" of
Sillett's study is that it shows "how difficult it will be to
reliably predict the effects of large scale regional climate
change on ecological systems."
SOURCE: The Associated Press
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