Deforestation Hurts Forces Migratory Birds into Poor Habitat
12/5/98
*******************************
RELAYED TEXT STARTS HERE:
Title: Deforestation Hurts Forces Migratory Birds into Poor Habitat
Source: Reuters
Status: Copyrighted, contact source to reprint
Date: 12/5/98
WASHINGTON (Reuters) -- The early bird gets not only the worm, but the
best shot at survival -- and poor winter habitat can hold back migrating
birds, researchers say.
They found songbirds forced into poor habitat in Jamaica were the
stragglers in getting back to their summer homes in New Hampshire, and
could not compete as well as a result. Only the strongest birds found good
homes in disappearing Caribbean forests, while the rest were forced to
make do with dry scrubland.
The findings released Friday by Peter Marra of the Smithsonian Institution
and colleagues at Dartmouth University and the Canadian Wildlife Service
could shed light on why so many bird populations are in decline.
"We've found that the quality of the winter habitat affects not only when
birds fly north to the breeding grounds but what condition they're in upon
arrival," Marra said in a statement.
"Both are crucial factors in how well the birds do on their summer
breeding grounds."
Early arrival advantageous
Marra's team studied American redstarts, which migrate between New England
and the Caribbean.
Redstarts spend three to five months in New England, six seven months in
the tropics, and the rest of the time migrating. But those who reach each
destination first --usually the most aggressive males -- get the best nest
sites and the best access to food.
"Early arrival appears to be advantageous because it gives access to the
best breeding sites and mates, as well as additional time to replace lost
clutches," Marra's team wrote in their report in the journal Science.
Birds who spent the winter in a moist mangrove forest in Jamaica did much
better than birds forced into a dry scrubland, they said.
"We found that individuals wintering in the forest habitat, regardless of
sex, maintained or gained body mass, whereas individuals in scrub habitat
lost up to 11 percent of their body mass," the researchers wrote.
And they were able to leave earlier in the spring, beating less fortunate
birds to the best homesteads in New Hampshire.
Many forests disappearing
In many areas, rainforests and temperate forests are giving way to
scrubland, both because of climate change and because people are clearing
them. But the study shows this can have long-term effects on the birds who
live in them, even part-time.
Marra's team said if more of the best winter habitat was available to the
birds, more would live there and thus more would be in good condition for
migration.
They used a new method that checks for traces of different forms of
carbon, known as isotopes. Plants growing in different areas develop
distinctive carbon signatures, w insects take up when they eat the plants.
The isotopes transfer to the birds when they eat the insects.
By testing their blood, the researchers could tell where the birds spend
their winters.
Copyright 1998 Reuters Limited