ENHS Nature Trails April 2005 Article 3

Alien Species Across the Atlantic
by Reida Kimmel

Several new birds are coming to feed outside our big window. The pair of collared doves (Streptopelia decaocto), whose plumage seems to be the very definition of 'dove grey,' are dainty feeders, keeping close together at all times. I repress a shudder at the other pairs, starlings and house sparrows! I remind myself that they "belong" in this country, and in some areas there is concern due to their declining populations. Both species really are quite attractively marked, and in no way aggressive at my feeding station. Indeed, it is the collared dove that is the alien, having just established itself in Britain about fifty years ago. And, I often find myself fighting ingrained prejudices about plants and animals here.

Whenever we are within a few miles of a coast, we see road banks and heathland covered in gorse. Often the plants are more than ten feet tall. Horrible stuff, I shudder. But no, it is native here, a source of nectar and pollen for numerous insect species, including honeybees and huge bumblebees. On a warm day, the scent is delicious. Ivy is everywhere, covering the ground, climbing up the beech, oak and ash trees. The trees seem to suffer no harm, and flowering as it does in the fall and early winter, the ivy provides late forage for bees. On Saturday we walked in Felbrigg Woods in Norfolk, under a canopy of Scots pine (Pinus sylvestris) and other evergreens. Small holly trees grow plentifully under the tall trees. A nuisance species for us, holly is common in mature, usually beech, woods in the south and midlands of England. The native birds relish the berries of this indigenous tree and disperse the seeds to the many newly planted woodlands. Conversely, all over the West of England, Ireland and Wales, rhododendron, escaped from gardens a century ago, is a beautiful lavender plague, and though it is grubbed out mercilessly, the battle seems lost.

Mammals introduced since the nineteenth century have also become destructive. The grey squirrel (Sciurus carolensis) has out competed England's red squirrel (Sciurus vulgaris), which is now found only in parts of Scotland and the protected island of Brownsea, in southern England. As in other parts of Europe, American mink (Mustela vison), escaped from fur farms, compete with the increasingly scarce otters for fish. Mink also prey on waterfowl. There is one success story: Nutria (Myocastor coypus), called copyu here, was establishing itself in many parts of England, especially in East Anglia, damaging the banks of watercourses and grazing on marsh and crop plants, but, with ruthless culling in the past decade, the numbers have been reduced approximately ninety percent.

The North Sea coast of Norfolk has miles of marsh, estuaries and long low sand and gravel spits of land, protected as internationally important wintering sites for migratory birds. Walking there on the Cley marshes on Sunday, we were happy to see three species of European geese and not a single Canada goose, a recent "gift" to Europe from North America that is seriously crowding the native birds. Skylarks filled the air with their lovely song. If there is such a thing as a benign export of a species, it could be skylarks. Some decades ago, someone imported skylarks to Vancouver Island Canada, and as the story goes, they established a colony on San Juan Island but nowhere else. If you wish to hear the song and watch the amazing flight displays of these rather drab brown birds, you need only to go to American Camp Park on San Juan Island and walk on the grassy moorland by the sea in spring.

We can generally agree that it is a dangerous thing to introduce a new species to an ecosystem, and that one of the many threats we perceive to our natural world is the planet-wide spread of invasive alien species. One could, I know, argue that such invasions have characterized life on this planet for eons. Look at the devastation to the native South American mammals when the Isthmus of Panama rose from the sea in the Pliocene, permitting the "more advanced" North American mammals to migrate south. The Devil's Advocate can also point to ethical dilemmas that occur in our increasingly managed natural world, when native species "go bad." Two such problems have been in the news here recently. Both concern highly charismatic "warm and fuzzy" species, which are going to be managed lethally. Badgers are totally cool animals, harmless omnivores. Videos taken in and around badger dens, called setts, amuse hundreds every day at parks like Heligan Gardens. But badgers harbor tuberculosis and badgers live in major dairy regions like the West Country and Wales. Biologists on both sides make strong claims, either that badgers do, or do not, give tuberculosis to cattle. Farmers insist they do, and it is a fact that there is a lot of the disease in England. A cow that tests positive for tuberculosis must be destroyed. Farmers want badgers living on or near their land to be killed. For several years there was a moratorium on killing while the issue was "studied."' Now the government has decided that a large "test" number of badgers will be culled in agricultural areas. Believe me, there will be protests if the killings begin! It really makes no sense to destroy an animal on the grounds that it might harbor tuberculosis. One could imagine trapping a family and testing it for the disease, destroying only the sick animals, but wholesale killing is really unjustified.

Another wildlife management issue in the newspapers is easier to understand. Thirty years ago a gardener in Scotland's Outer Hebrides introduced hedgehogs to control slugs. They subsequently spread to three of the archipelago's closely connected islands and became a major predator of the eggs of ground nesting seabirds. Imagine Mrs. Tiggywinkle versus the adorable puffins for a real conflict of emotions! Because moving the animals to areas where they naturally occur on the mainland would disturb the local populations, the Scottish Natural Heritage has been culling the hedgehogs annually, killing 253 last year. This year's cull is about to begin, and members of the British Hedgehog Preservation Society and the Hessilhead Wildlife Rescue Trust have set up a camp and a veterinary station near the Benbecula airport, hoping to rescue and relocate as many of these lovable insectivores as they can. Let's just hope they don't plan to export them to North America!

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