A priceless part of the Natural History Museum’s collection of tropical bird skins has been stolen.

Almost 300 brightly coloured specimens were taken from the ornithological collection in Tring, Hertfordshire, by thieves who are thought to have stolen them to order, possibly for a collector.

Detectives are investigating whether the birds could have been taken over a period of time by someone with official access to the museum, such as an academic or researcher. The curators said that some were more than a century old; they also fear that the birds could be ripped apart for use in dressmaking or as fishing lures.

Professor Richard Lane, director of science at the museum, said that the specimens were of great historical importance and might prove impossible to replace. “It is quite hard for us to express just how tragic this is to members of the museum,” he said. “This is the nation’s collection. These birds are extremely scarce: they are scarce in collections and even more scarce in the wild. Our utmost priority is working with the police to return these specimens to the national collections so that they can be used by future generations of scientists.”

Museum officials were relieved to discover that none of their most valuable birds had been taken from the private research area after the break-in was discovered in June. More than 8,000 “specimen types” — perfect examples of bird species — and finches collected by Charles Darwin in the Galápagos Islands were left untouched.

Several days later, though, it was found that several brightly coloured bird skins were missing. Experts then spent weeks examining the full extent of the theft as they checked more than 500 cabinets on three floors. Eventually they realised that 299 birds had disappeared.

The thieves had taken quetzal and cotinga birds, from Central and South America, and birds of paradise from Papua New Guinea. All of the missing birds had bright plumage, whereas female specimens left behind had brown feathers. Police believe that whoever is responsible had detailed knowledge of the birds. The cabinets were labelled with Latin names organised in evolutionary order and most of the vast collection was left undisturbed.

Detective Inspector Fraser Wylie said that 299 birds could fill up to six bin bags and some specimens had tail feathers more than 3ft long. “This is a very unusual crime and we are keen to recover the bird skins, which are part of our national heritage,” he said. “Some of these may be irreplaceable. We are appealing for help from anyone who may have seen any suspicious activity around the museum at the time of the break-in. Also, we would ask any collectors of such specimens to keep a watchful eye out in case they are offered anything resembling them.

“Clearly there are collectors who may want these species. There may be a need within the fishing market because of the colour of the feathers and there is a theory they could be used in dresses and jewellery.”

The missing birds were all preserved “skins”, from which all internal organs and eyes had been removed. Researchers study feather patterns and other features to learn about how the birds have evolved. The museum holds 70 million specimens collected over 350 years, most of them at its South Kensington headquarters. The collection at Tring is one of the world’s largest and holds 750,000 birds, representing 95 per cent of all known species.

Anyone with information should contact Mr Wylie on 0845 3300222.

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