San
Francisco, CA (8/18/98)- As the hornbill goes, so goes the rainforest
ecosystem, suggests new research from a team of California biologists.
With a massive bill for crunching nuts and seeds, a raucous screech
and and wingspan of up to four feet, the hornbill is one of the most distinctive
birds in the African rainforest. Once thought to occupy small zones in
the forest, current research indicates the birds actually travel widely
in search of food, dispersing seeds and playing an hitherto unsuspected
role in forest regeneration
Biologists at San Francisco State University and the University of California
at Davis studied three species of hornbills for three years in the Cameroon
rainforest. They discovered that the toucan-like birds disperse seeds of
nearly a fourth of the tropical trees, flying 100 miles or more through
the forest in search of ripening fruit. Until this study, the birds were
thought to be sedentary, residing throughout the year in patches of rainforest.
The new data reveals that three hornbill species feed on about a
quarter of all trees in the rainforest -- 59 species in all. The Cameroon
study found that nearly all the seeds dispersed by the hornbills germinate
successfully, making the birds one of the prime agents of lowland rainforest
regeneration.
"The survival of the rainforest appears to rely to a large degree on
the hornbills' ability to disperse seeds of so many species. If we have
any hope of protecting rainforests we need to protect not just the pattern
of biodiversity but also the processes that create it. Our work suggests
that by dispersing seeds, these magnificent birds are vital agents of biodiversity.
The birds' surprisingly large range suggests that their own survival depends
on preserving large expanses of rain forest intact," said Thomas Smith,
associate professor of biology at San Francisco State University.
"Hornbills were thought to live in relatively confined rainforest habitats,"
said Ken Whitney, who led the seed dispersal studies as a graduate student
at San Francisco State. "But this research shows that the movement pattern
of a few hornbill species may be more like that of elephants and some primates,
rather than forest birds." And as other important seed dispersers such
as elephants and primates continue to decline in the region due to habitat
destruction and hunting , hornbills become even more important for rain
forest regrowth and survival, he emphasized.
Tracking hungry hornbills through the dense rainforest is no mean feat.
To simply the task, Smith and colleagues are starting to work with scientists
at the Wildlife Conservation Society and NASA's Jet Propulsion Laboratory
to track the birds' movements by satellite. The biologists will attach
small radio transmitters on up to 30 hornbills, and NASA will track their
whereabouts.
The
research appears in the August 1998 issue of the Journal of Tropical Ecology
and Animal Conservation.
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