Rum health diet drives deer to snack on chicks

Horrified bird watchers on the Isle of Rum have discovered the tiny headless and legless corpses of Manx Shearwater chicks who have fallen prey to carnivorous deer.

Scientists believe the normally docile beasts are eating the baby birds to make up for deficiencies in their diet on Rum, or even using them as a form of medicine.

Rum, a national nature reserve owned and run by Scottish Natural Heritage is the main breeding colony for Manx shearwater, with an estimated 100,000 pairs or a fifth to a third of the world population.

Reserve manager Mick Blunt said: "You see plenty of Manx shearwater corpses without their heads. I am planning to carry out a bit of research through our archives to see when this phenomenon was first spotted.

"Perhaps the deer need calcium for antler growth, or possibly they are after other trace elements. There have been umpteen reports of the meat-eating deer.

"National Geographic apparently are planning a visit later this year with infra-red cameras to see if they can film the deer attacking the shearwater.

"But despite so many threats to the shearwater, the colony seems to be thriving and they don’t appear to be in any danger. There can be 200,000 birds on the hillside, so if 1% to 2% were killed it would have little impact."

Nick Reiter, director of the Deer Commission for Scotland, said they had received reports of meat-eating deer on Rum but had not yet researched it.

He said: "Why they do it is a matter of speculation and I can’t imagine it is a regular thing. However, red deer will eat shed antlers. Maybe these birds just taste nice, and after a hard day on the heather and grass the deer are saying, ‘I could murder a shearwater.’"

When not under threat from deer and other predators on Rum, the shearwater spends the winter bobbing in the sea off Brazil.

Glasgow University’s Dr Bob Furness, who has written about sheep eating live tern and skua chicks on Foula, Shetland, agrees the Rum deer are alleviating a mineral deficiency in their diet.

Calcium levels in the vegetation are low on Rum, he said, and bird killing could happen in both mineral-deficient areas with high densities of ground-nesting seabirds. "I’m happy the likely reason is mineral deficiency. Experiments in Australia showed that cattle made mineral deficient went seeking bones, even taking plaster of Paris made up with stewed bone extract."

Also Furness knew of old accounts of red deer taking grouse chicks on a Scottish grouse moor in the 19th Century.

The shearwater chicks are at their most vulnerable this month when they are just emerging from the burrows dug for them by their parents in the crumbly volcanic soil near the summit of the Rum Cuillin.

They face a host of predators, including sea eagles, golden eagles, peregrine falcons, black-backed gulls and rats.

The adults have a hard enough life as it is, flying out to sea as far as 200 miles to catch fish for their young. They then navigate back in the dark and head for their burrows before any predators catch them regurgitating the fish for their greedy chicks. If it is a very bright night with a full moon, they have been known to stay out at sea to avoid being eaten.

But the youngsters don’t know to avoid the bright nights and it is then that the deer can catch them.

Two years ago, Scotland on Sunday revealed that sheep had been seen eating exhausted migratory birds on the Orkney island of North Ronaldsay.

And as with the Rum deer, the Orkney sheep displayed a predilection for the crunchy bits of their prey, their legs and beaks in particular.

Explanations for the sheep’s strange behaviour varied from supplementing their diets to the theory the birds were getting in the way of ruminants trying to eat seaweed.

Cindy Engel, of the Open University, who has written Wild Health: How Animals Keep Themselves Well, said the bird-eating deer of Rum and sheep of Orkney are just two examples among dozens of animals actively taking care of their health.