BEIJING, July 9 (Xinhuanet) -- Gangs of house mice on Gough Island in the South Atlantic have been videotaped invading the nests of young seabird chicks and gnawing through chicks' feathers and skin before gorging on their entrails.

While islands represent a small fraction of Earth's land area, they are home to a relatively large percentage of bird species. Since 1600, more than 90 percent of avian extinctions have occurred among island species, say the authors of the new study published in the journal Biology Letters.

Many of the extinctions have been blamed on invasive mammals, especially rats, and conservation efforts have focused on eradicating the non-native rats from such islands. Mice been thought of as no threat to seabirds and left to populate islands sometimes without competition from their rat relatives, which is what happened on Gough Island.

Between January and September 2004, Ross Wanless of the University of Cape Town in South Africa and his colleagues monitored 300 Tristan albatross (Diomedea dabbenena) nests. They examined chicks for wounds about three times a month and filmed chicks using an infrared video recorder.

They also monitored and video recorded three great shearwater (Puffinus gravis) and 60 Atlantic petrel (Pterodroma incerta) chicks.

Mice were caught on video gnawing on and often killing live chicks of all three bird species. One video showed up to 10 mice mauling an albatross chick and eating from three open wounds on its body.

By late September 2004, 100 of the 256 monitored albatross chicks had died. Before the mouse attacks, all the chicks were apparently healthy, suggesting the rodents seek out weak or sick chicks.

At the end of the study, the researchers calculated a breeding success of just 27 percent for the albatross, which is "unprecedented" for this species. Typically, about 60 percent to 70 percent of the chicks survive. Mice also attacked the Atlantic petrel chicks as soon as the babies hatched in July 2004, and by September 2004, just 20 of the 60 monitored chicks were still alive.

(Agencies)