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October 03, 2002
Galapagos Islands Warning
BirdLife International has warned that the bird life of the Galapagos Islands, Ecuador, may be facing a new threat from flies, the larvae of which feed on nestling birds. At least three species of fly, presumably accidentally introduced, have recently been discovered on the islands (the first in 1997). A paper in Ibis 144: 445?451 reports on nesting success and nestling mortality of both native and introduced bird species affected by the flies parasitic larvae.
Although parasites that have evolved a host-parasite relationship often do not seriously harm their host populations, those brought into parasite-free populations often cause severe harm before defence mechanisms evolve. For example, in Hawaii the accidental introduction of a mosquito species allowed the spread of avian malaria and resulted in the extinction of many endemic bird species.
Researchers found that on the island of Santa Cruz, 97% of endemic finch nests were infected by the ectoparasite Philornis downsi, with an average of more than 23 parasites per nestling and a relatively high nestling mortality of 27%. Although it is difficult to be certain that parasites caused nestling deaths, malnutrition did not seem to be a factor and infestation may have severely weakened nestlings as birds with holes in the back, neck and under the wings were discovered.
The potential impact of the newly discovered parasites may be massive, and further study of the scale of the threat is urgently needed. Currently, flies seem to be absent from small dry islands, where adults may be unable to survive without a humid climate.
The above news item is just one of many from the forthcoming December 2002 issue of BirdLife International's World Birdwatch magazine, the essential magazine for world birdwatchers.
Other news items include the recognition of at least six new species world-wide, including a new European endemic...
For details of how to subscribe, see www.birdlife.net/help/wbwmag.cfm
Posted by Surfbirds at October 3, 2002 11:18 PM
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