Partying round the clock usually takes its toll - unless you happen to be a sex-mad male pectoral sandpiper.

The birds avoid sleeping for weeks on end so as not to miss out on mating opportunities.

Scientists found they spent up to 95% of their time awake, yet appeared to suffer no ill effects.

Those allowing themselves to snooze were likely to lose out to their rivals.

Birds that slept least during the breeding season produced the most offspring, the research showed.

Their behaviour calls into question the widely-held view that sleep is vital to regenerate the brain and maintain mental performance.

The polygamous pectoral sandpiper breeds for three weeks in the constant daylight of the Arctic summer.

Each male might mate with several females - but sex is no easy affair.

"Males have to constantly repel their rivals through male-male competition and simultaneously convince females with intensive courtship display," said study leader Dr Bart Kempenaers, from the Max Planck Institute for Ornithology at Seewiesen in Germany.

Males competed in "aerial chases" of females and engaged in physical fights.

Females, on the other hand, were "very reluctant" to surrender to male advances.

In an environment where the sun never sets, male birds that pursued the opposite sex 24/7 were at an advantage.

The researchers, whose findings are reported in the journal Science, studied pectoral sandpipers at one of the birds' breeding grounds in Alaska.

Transmitters attached to the birds allowed the scientists to track when they were moving or resting.

Brain activity recordings confirmed that inactive birds were sleeping.

The male birds were active for up to 95% of the time, the scientists confirmed.

Those that stayed awake the longest slept the deepest when they did finally manage to rest.

DNA analysis showed that these birds also produced the most offspring.

Their ability to defeat sleep was all the more remarkable given that they arrived at the breeding ground after journeying thousands of miles from the southern hemisphere.

The scientists wrote: "Male pectoral sandpipers.. are able to maintain high neurobehavioral performance despite greatly reducing their time spent sleeping during a three-week period of intense male-to-male competition for access to fertile females.

"Males that slept the least sired the most offspring.

"Our results challenge the view that decreased performance is an inescapable outcome of sleep loss."