The following item illustrates the importance of effective quarantine for
ecological conservation ...
http://www.birdlife.org.uk/news/pritem_display.cfm?NewRecID=709&NewType=P
Parasites pose new threat to Darwin's finches
08/11/02
Cambridge, UK, Friday 8th November 2002 -- BirdLife International today warned
that Darwin's finches - made famous by Charles Darwin's theory of evolution -
are facing a new and, for some species, potentially major threat from parasitic
fly larvae which feed on nestling birds in the islands of the Galapagos
archipelago, Ecuador [1,2,3].
At least three species of fly are thought to have been accidentally introduced
to the islands, the first having been found in 1997. A paper published in the
latest issue of the ornithological journal, Ibis [4], reports on nesting success
and nestling mortality of 12 native and introduced bird species affected by the
flies' parasitic larvae, including seven of the 13 Darwin's finch species, each
of which were found to have the new parasitic fly larvae in their nests.
"The potential impact of the newly discovered parasites may be major, and
further study of the scale of the threat is urgently required", says Birgit
Fessl of the Konrad Lorenz Institute, one of the paper's authors.
"Most worrying is the presence of these new parasites on Isabella Island, the
only place in the world where the Critically Endangered Mangrove Finch
Camarhynchus heliobates occurs. This is the most threatened of the Darwin's
finches and numbers 110 individual birds in the wild", says BirdLife
International's Dr Nigel Collar, author of Threatened Birds of the Americas
[5,6]. "A decline in nestling survival resulting from these new parasitic fly
larvae would severely threaten this already critical species with extinction."
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. Some have
caused avian
extinctions.
"For example, in the Hawaiian Islands, USA, the accidental introduction of the
mosquito Culex pipiens fatigans in the 19th Century, a vector for avian malaria,
led to the extinction of several endemic bird species, including the Kaua'a 'O'o
Moho braccatus, 'Akialoa Akialoa obscura and Hawai'i Mamo Drepanis pacifica",
said Dr Collar.
More recently, White-rumped Vulture Gyps bengalensis, Slender-billed Vulture
Gyps tenuirostris and Indian Vulture Gyps indicus have declined dramatically in
Asia by over 90% since 1994, and are now classified as Critically Endangered
by the IUCN Red List of Globally Threatened Species. These declines are strongly
believed to be linked to an as yet unidentified disease.
On the Galapagos island of Santa Cruz the researchers found that 97% of the
endemic finch nests studied were infected by the fly ectoparasite Philornis
downsi, with an average of more than 23 parasites per nestling and a relatively
high nestling mortality of 27%. Although the researchers say it is difficult to
be certain that parasites caused nestling deaths, malnutrition did not appear to
be a factor and infestation may have severely weakened nestlings because birds
with holes in the back, neck and under the wings were discovered.
BirdLife International has today written to the Ecuadorian Environment Minister,
Lourdes Luque, alerting the Government in Ecuador to this new threat to Darwin's
finches, and requesting that it prioritise research into the impact of the new
parasites and consider taking additional action to prevent further accidental
introductions of exotic parasitic insect species to the Galapagos archipelago.
NOTES FOR EDITORS
1. BirdLife International is a global alliance of national conservation
organisations working in more than 100 countries who, together, are the leading
authority on the status of birds, their habitats and the issues and problems
affecting bird life.
2. In Origin of Species Charles Darwin cited the variety of finch species in the
Galapagos archipelago as an example of adaptive radiation, theorising that each
evolved from a common ancestor species having adapting to the different niches
available. It is from this famous example that they became known as Darwin's
finches.
3. List of Darwin's finch species (* denotes a species studied in the recent
Ibis paper):
Medium Ground-finch Geospiza fortis*
Small Ground-finch Geospiza fuliginosa*
Common Cactus-finch Geospiza scandens*
Large Tree-finch Camarhynchus psittacula*
Small Tree-finch Camarhynchus parvulus*
Woodpecker Finch Camarhynchus pallidus*
Warbler Finch Certhidia olivacea*
Mangrove Finch Camarhynchus heliobates
Large-Ground-finch Geospiza magnirostris
Sharp-beaked Ground-finch Geospiza difficilis
Large Cactus-finch Geospiza conirostris
Vegetarian Finch Camarhynchus crassirostris
Medium Tree-finch Camarhynchus pauper
4. Birgit Fessl and Sabine Tebich, Philornis downsi - a recently discovered
parasite on the Galapagos archipelago - a threat for Darwin's finches. Ibis.
July 2002 144: 445-451.
5. BirdLife International is the official listing authority for birds for the
World Conservation Union (IUCN) Red List. The Red List criteria for globally
threatened species are: Critically Endangered (facing an extremely high risk of
extinction in the wild in the immediate future), Endangered (facing a very high
risk of extinction in the wild in the near future), and Vulnerable (facing a
high risk of extinction in the wild in the medium-term).
6. N.J. Collar et al, Threatened Birds of the Americas, The ICBP/IUCN Red Data
Book, 1992, ICBP, Cambridge.
Birding-Aus is on the Web at
www.shc.melb.catholic.edu.au/home/birding/index.html
To unsubscribe from this mailing list, send the message
"unsubscribe birding-aus" (no quotes, no Subject line)
to
|
