Passengers setting off on long-haul flights have to pack carefully to avoid heavy fines for excess weight but the bar-tailed godwit goes a stage further. Having stuffed itself to its wing tips in preparation for its 11,000km migratory flight from Alaska to New Zealand, it destroys part of its gut, liver and kidneys to save weight.

The wading birds, about the size of a gull, binge before they migrate, until more than half their body weight is fat. Dutch and US scientists who compared organ weights of the birds report in New Scientist that they were reduced in size by up to 25 per cent. Digestive organs are not required during the flight but they keep just enough so that when they land they can process food and rebuild their internal organs.

A few herbs, and a very big business

Seven million Germans regularly take Hypericum Perforatum as a herbal antidepressant. In the US, sales of Gingko extracts and ginseng exceed $50m. China earns at least $400m a year from the export of herbal medicines. This is the financial backdrop to an international conference on medicinal and aromatic plants which was held in Mendoza, Argentina. It heard that new anti-microbial compounds had been isolated from Chilean plants and a new type of cytotoxic compound isolated from a Podocanthus species had attracted the interest of the National Institutes of Cancer Research in the US.

You need never miss your stop again

People who habitually nod off on the train home and miss their stop may soon be able to buy an intelligent alarm that will jerk them awake at the appropriate moment. Clive Wallington of Colchester, who has patented the device, says in New Scientist that the guard's announcement is often too late, incoherent or not loud enough to wake a sleeping passenger. Using Wallington's invention, beacons by the track a few kilometres ahead of each station transmit a signal to the alarm. On receipt of the signal the alarm bleeps to wake the traveller.

Can Aids ever be finally eliminated?

Scientists disagree over whether the Aids virus can ever be entirely eradicated from the bodies of those infected. Dr Gary Tarpley, of the drug company Pharmacia and Upjohn, told the Chicago Aids conference this week that the "evasive" virus would pose a "permanent challenge". "I personally think it is very unlikely that we will ever eradicate this virus from an infected patient." Not all scientists share this sceptical view. Dr B Hoen and colleagues set out to test whether eradication of the virus was possible in 65 patients treated with the protease inhibitor Ritonavir, in combination with AZT and 3TC. In 17 of 18 patients who completed the course at one year the reduction in viral load was over 99.95 per cent - below the detectable level. They will be followed up for 18 months.

Another line on mobile phones

Mobile phones which need recharging every four days, rather than every two hours as now, could be on sale within a couple of years. A tiny fuel cell using methanol as its energy source has been developed by a former scientist at the Los Alamos National Laboratory. Last month a Californian venture capital company agreed to invest $1m on developing a prototype.