London, Feb 9 (IANS) Migrating insects fly at heights where the wind currents are fastest, enabling them to undertake journeys of several thousands of kilometres in a shorter duration of time, research says.

Many insects avoid cold British winters by migrating south in autumn to over-wintering sites around the Mediterranean. These migrant insects then return to Britain in spring.

The new study was funded by Biotechnology and Biological Sciences Research Council (BBSRC) and used two sets of specially-designed radar equipment to observe migrating butterflies and moths flying several hundreds of metres above the ground.

These insect migrants have a compass sense that enables them to select winds which will take them in their chosen direction, and to travel at speeds of up to 100 kmph.

The fast speeds of winds aloft mean that insects travel more-or-less downwind, but they make subtle adjustments to their headings so that they are partially correct for wind-induced drift away from their preferred direction of travel.

BBSRC's Jason Chapman said: 'Migratory butterflies and moths have evolved an amazing capacity to use favourable tailwinds. By flying at the heights where the wind currents are fastest, migratory moths can travel between their summer and winter grounds in just a few nights.'

The study used a computer model dubbed 'NAME' to demonstrate that the flight behaviours observed result in migrants travelling nearly twice as far and closer to their preferred direction as an insect just randomly drifting downwind.

Many migratory insects are pests of agricultural crops, so the model will be useful for predicting migration events in the future, said a BBSRC release.

The findings were published in Science.