http://www.int.iol.co.za/
index.php?set_id=1&click_id=143&art_id=nw20070518000442428C407742
Contaminated lake is mystery bird magnet
May 18 2007 at 02:01AM
By Alberto Barrera
Cerron Grande Reservoir - An artificial lake in El Salvador brimming
with sewage and industrial waste is mystifying scientists by attracting
thousands of migratory and sea birds.
Built in 1974 to drive El Salvador's biggest hydroelectric project, the
13 500- hectare Cerron Grande reservoir collects about 3 800 tons of
excrement each year from the sewage pipes, as well as factory run-off
and traces of heavy metals like chromium and lead, the government
estimates.
So scientists are puzzling over the fact that about 150 000 seabirds
from more than 130 species have chosen to make the reservoir their
home. At least 90 of the species are migratory birds arriving from as
far away as Alaska.
"It's one of the most contaminated lakes we have, which is why we
should carry out a study on why the birds are here," said marine
biologist Oscar Molina.
Waste from 54 industrial plants, 55 coffee processing plants, seven
sugar mills and 29 sewerage systems flows into the reservoir, the
environment ministry found in a 2004 study.
Yet the birds attracted to the lake even outnumber the roughly 100 000
people living in villages around it.
On one of 28 islands dotting the reservoir, biologists discovered 46
nests made by migrating American storks who produced some 100 chicks at
the start of the year.
Biologists have been monitoring bird numbers at the reservoir since
2001, but Molina said El Salvador lacked the funds to carry out a full
investigation into why so many are attracted to the area.
Environment ministry ornithologist Ricardo Ibarra said birds may be
attracted by the sandy beaches, crawling with insects, that appear
around the edge of the lake in the dry season.
"The most relevant thing is why the stork is nesting here for the first
time," Ibarra said.
But the contamination is bound to be harming birds that feed and nest
there, possibly making them too weak to be sure of making their
migratory flights or affecting the strength of the shells of their
eggs, he warned.
In a worrying sign, agronomist Edgardo Erazo, who studies wildlife on
the reservoir, said scraps of plastic and metal - and even plastic
clothes pegs - had been discovered in bird nests around the lake.
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