By Mark Kinver
Science and nature reporter, BBC News
Marquesan imperial-pigeon is a success story
Climate change is "significantly amplifying" the threats facing the world's bird populations, a global assessment has concluded.
The 2008 IUCN Bird Red List warns that long-term droughts and extreme weather puts additional stress on key habitats.
The assessment lists 1,226 species as threatened with extinction - one-in-eight of all bird species.
The list, reviewed every four years, is compiled by conservation charity BirdLife International.
"It is very hard to precisely attribute particular changes in specific species to climate change," said Stuart Butchart, BirdLife's global research and indicators co-ordinator.
"But there is now a whole suite of species that are clearly becoming threatened by extreme weather events and droughts."
In the revised Red List, eight species have been added to the "critically endangered" category.
One of these was the Floreana mockingbird (Nesomimus trifasciatus), which is confined to two islets in the Galapagos Islands.
CRITICALLY ENDANGERED - NEW ADDITIONS
(Source: Bird Red List 2008 update)
From an estimated maximum of 150 in the mid-1960s, the population has fallen to fewer than 60.
Conservationists listed the mockingbird as Critically Endangered because it experienced a high rate of adult mortality during dry years that have been linked to La Nina events.
Dry years have become more frequent in recent years, and have been blamed as the main driver of the current decline.
"Another threat for small island species, such as the Floreana mockingbird, is the threat from invasive species, in particular mammals and plants," Dr Butchart told BBC News.
"They are having a devastating effect on habitats. For example, goats and donkeys on Floreana are changing the ecological structure.
"Eliminating or controlling invasive species is a very tractable conservation action that can help these birds hang on in the face of these additional pressures from climate change.
Floreana mockingbird now numbers fewer than 100 birds
"The key actions that are needed to prevent a species like this from going extinct are the very broad-scale climate-change mitigation measures - such as reducing our carbon emissions, limiting the global average temperature rise to no more than 2C (3.6F), and changing society's values and lifestyles."
Dr Butchart said another example of a species being affected by shifts in the climate was the akekee (Loxops caeruleirostris), a Hawaiian honey-creeper.
"Not only is it being negatively impacted by prolonged heavy rain causing nesting failures, but they are extremely threatened by introduced diseases, which are carried by invasive mosquitoes.
"The mosquitoes have been restricted to lower altitudes, so the birds do best at heights above which the mosquitoes can go and pass on avian malaria.
"But because of climate change, the temperature zones are shifting. It is getting warmer at higher altitudes, so the mosquitoes can now move higher.
"This is eliminating the mosquito-free zone that the birds used to occupy."
More continental species, such as the Eurasian curlew, are struggling
As a result, Dr Butchart explained, this bird was also being uplisted to the status of Critically Endangered.
Despite the latest assessment showing a continuing downward trend in the world's bird populations, he said that conservationists were still optimistic that many species could be saved.
"It is undoubtedly true that we are facing an unprecedented conservation crisis but we do have conservation success stories that give us hope that not all threatened species are doomed.
"We have the solutions but what we need are the resources and political will."
BirdLife International has recently launched its Preventing Extinctions Programme, which targets the 190 species listed as Critically Endangered.
Its goal is to find a "species champion" for each bird, who will fund the on-the-ground conservation work of "species guardians".
"Success stories provide us with the great hope that this can be achieved, provided that we act soon enough."
Hawaii's Maui parrotbill is another clinging on to existence
One bird that has been downlisted from Critically Endangered to Endangered in the latest assessment is the Marquesan imperial-pigeon (Ducula galeata).
The main threat facing the bird came from rats, an invasive species.
In order to protect the population of the slow-breeding birds, conservationists moved 10 adults to a neighbouring rat-free island between 2000 and 2003.
The new community of pigeons is now established on the island, and conservationists are hopeful that the population will reach 50 by 2010.
"This has greatly reduced the extinction risk because the bird is now spread over a couple of islands," observed Dr Butchart.
"This goes to show not only that conservation works but that it is vital if we are to prevent the extinction of these and other species."