Puffins dig their own graves

Puffins on the island of Craigleith, in Scotland, are being forced out by giant alien plants. Puffin numbers have halved in recent years as the invasive tree mallow took over the island, growing in the manure-rich burrow entrances and preventing the puffins from breeding.

Although Atlantic puffin numbers are increasing rapidly across most of the east coast of Scotland, at Craigleith near North Berwick the reverse has been the case. The decline has been blamed on the rapid expansion of the tree mallow which grows in dense stands up to 3m tall and prevents the puffins from accessing their burrows. The number of burrows in which puffin pairs breed reduced from 28,000 in 1999 to 14,000 in 2003.

Scientists are now asking people for help, as part of a new three-year study funded by the Scottish Executive. The researchers need to find out why the tree mallow has suddenly expanded and develop practical approaches to control its growth.

Project leader Dr René van der Wal from the Centre for Ecology & Hydrology in Banchory said “We need help to sort this problem out. The tree mallow expansion is probably due to recent mild winters and the efforts of the puffins which provide great conditions for tree mallow to grow. However we have very little information and need to know more, fast.”

He added, “People can help us in three ways. First, they can visit our new tree mallow website to find out more about the problem and how to identify the alien plant. Second, we’d like them to both alert us and send in any photos, new and old, of coastal areas where tree mallow has been seen growing. Third, we would really like some local schools to get involved by planting tree mallow seedlings outside their classrooms and letting us know how they grow as the weather changes. We shall, of course, ensure that no seedlings escape.”

Scottish Natural Heritage and the Scottish Seabird Centre at North Berwick are also involved in the project. Lillian Kelly from the Seabird Centre said “We’re really excited about this new project. It provides us with a great opportunity to run school activity days focussing on how global climate change is having obvious local impacts, for example on the puffins as tree mallow plants take hold. Birdwatchers come to Scotland from round the world to see our seabirds and we must conserve this vitally important tourist resource.”

The puffins themselves assist in the establishment of tree mallow, which needs a fertile soil to establish itself. Soils of seabird islands are nitrogen rich as a result of the guano and ammonia from seabirds faeces. Tree mallow seedlings grow predominantly in gaps in the vegetation that are created by puffins through their digging, or in areas that puffins frequently use.

Tree mallow is believed to have escaped into the wild in East Scotland after being planted in coastal gardens. In particular, lighthouse keepers grew the plants and used the large woolly leaves as an effective compress to cover wounds. Whereas tree mallow has been on the Bass Rock for more than three centuries, the species has rapidly expanded on other islands during the last fifteen years in the Firth of Forth region. Scientists do not know why this is the case. Hopefully this mystery will be resolved within this project.