Birdwatchers at the London Wetland Centre in Barnes were shocked when a rare bird they had come to watch was devoured by a sparrowhawk in front of their eyes.

The spotted crake, a diminutive member of the rail family of birds, was spotted at the centre last month but suffered an untimely demise on when a sparrowhawk swooped and grabbed it.

Mike Waite, an eye-witness, said: "It was just after 4pm. A group of around a dozen visitors were watching the juvenile spotted crake through binoculars and telescopes as it obligingly fed out in the open along the muddy edge of the wader scrape.

"All of a sudden a handsome male sparrowhawk swooped down and grabbed the bird in its talons.

"The latter struggled feebly for a short while, but the sparrowhawk maintained its vice-like grip until flying off with its still twitching prey in its talons, into a tree on the Thames bank, to consume its rare victim.

"Everyone in the hide was universally shocked, and outraged in a slaughter-of-the-innocents kind of way. The crake learned in the hardest possible way why its conspicuous behaviour was unbecoming of this species."

The spotted crake was a rarity at the London Wetland Centre. The last time this species was seen at the centre on the banks of the River Thames was in 1999, before it opened to the public.

A spokesperson for the London Wetland Centre commented: "It was quite a shock for visitors to see this rare bird come to such a violent end, but what they saw was evolution in action.

"The inexperienced juvenile spotted crake had been clearly visible for several days in the same area, it was only a matter of time before it came to the attention of a hungry predator. This experience shows why this species is normally shy and secretive."