Ian Carter
Ian Carter

We are lucky here in Britain that the majority of our most widespread and familiar birds are the same native species that have been living here for thousands of years. Most were here before humans started to have a major impact on the landscape and, with varying levels of success, they have adapted to the changes we have brought about. Other island countries have been far less fortunate. In New Zealand, for example, the introduction of invasive predatory mammals has decimated the native bird fauna. Many of the remaining species are now restricted to offshore islands or a few remaining patches of natural forest where they are protected from predators by huge, electrified fences and poison baits. Unsurprisingly, the control of invasive non-native species in New Zealand is pursued vigorously, to try to save what is left, and tends not to be seen as contentious. In contrast, the control of non-natives is often highly contentious in Britain and there are some extreme views on both sides of the argument, particularly when it comes to birds and mammals. One view is that, ideally, we should be rid of the lot of them - none have a right to be here and they inevitably compete with native wildlife for food or other resources. Practicalities make eradication of all non-natives impossible, of course, though the development of new technologies such as oral contraception could widen our aspirations in future. At the other extreme are those who say 'live and let live'. If non-natives become established as a result of human intervention, then so be it - they have just as much right to an existence as any of our long-established native species. I'm somewhere in between the two views outlined above, although leaning far more towards getting rid of the lot of them. I could happily live without introduced Canada Geese Branta canadensis, Egyptian Geese Alopochen aegyptiaca, Mandarin Ducks Aix galericulata, Ruddy Ducks Oxyura jamaicensis, Red-legged Partridges Alectoris rufa, Common Pheasants Phasianus colchicus, Monk Parakeets Myiopsitta monachus, Mink Neovison vison, Grey Squirrels Sciurus carolinensis and Fallow Deer Dama dama, to name just a few. As highlighted recently by Jeremy Greenwood (Brit. Birds 106: 240), biodiversity means more than local species richness. It is about maintaining differences on a larger scale, rather than accepting a similar mix of species across large parts of the globe. I am, however, conscious of some apparent inconsistencies and even confusion in my own views. I would, for example, be very reluctant to see the back of the Brown Hare Lepus capensis, Rabbit Oryctolagus cuniculus and Little Owl Athene noctua, for reasons that I'm not sure are entirely defendable. As with the control of native wildlife (Brit. Birds 106: 490-491), our views on non-natives are influenced not only by sound evidence and logic but also by our own experiences and personal prejudices. The Brown Hare is one of my favourite mammals and one I see regularly in the fields around our house in northeast Cambridgeshire. It has adapted well to intensively-managed farmland and often appears to be the only living thing eking out an existence in some of the more barren arable fields in this area. Although introduced originally by humans, it has been with us, sharing our landscapes, for thousands of years. Is it justifiable to treat it as an honorary native because of this? Perhaps, though already I fear the lines are starting to blur. The Rabbit has not been here for as long as the Brown Hare but long enough for it to have become deeply integrated into our ecosystems and food webs. It maintains our remaining flower-rich semi-natural grasslands by keeping the sward short. And it is a vital food source for a whole array of native fauna including Red Foxes Vulpes vulpes, Stoats Mustela erminea, Common Buzzards Buteo buteo and Red Kites Milvus milvus. Removing this non-native from the landscape would have profound effects on many native species. Should we therefore welcome this species? We are lucky enough to have Little Owls nesting in one of the mature trees in the garden. The nest hole is overlooked by my study and for three years running they have provided a welcome distraction from the computer screen throughout the breeding season. The Little Owl was introduced relatively recently and as a pugnacious defender of nest holes it certainly has the potential to affect native species. Scraps between the adult owls and the local Stock Doves Columba oenas are frequent in spring and often end with feathers of the native species floating down onto the lawn below. Logic suggests that Little Owls should not be welcomed. The only defence I can offer is that the Little Owl's native range includes most of Europe and it is found just across the English Channel on the near Continent. The fact that it has not made it to Britain is, it could be argued, a mere quirk of geography and rising sea levels. Had things been different, then it could very well have spread here naturally. Is it reasonable to treat it as another honorary native? The problem with these arguments is that they blur the boundaries between natives and non-natives. Everyone's criteria for what may constitute an 'honorary native' will be different. Everyone will have their own favourite species for which they can make a special case. How far back does an introduction need to be before the species should be accepted? How close does the native range have to be? How entrenched in our ecosystems must a species become before it is spared? I love watching Brown Hares and Little Owls but is it really tenable to defend them and, at the same time, wish that Grey Squirrels and Rose-ringed Parakeets Psittacula krameri could be eradicated? In more troubled moments I wonder if we can ever expect to develop a coherent approach to non-native species. The consequences of taking no action, however, are considerable. While we are fortunate in comparison with places like New Zealand, the adverse effects of invasive non-natives have been well documented and our vertebrate fauna is becoming more and more dominated by them. The Rabbit, Grey Squirrel, Brown Rat Rattus norvegicus, House Mouse Mus musculus and Muntjac Muntiacus reevesi are among our most familiar mammals. And Pheasants, Red-legged Partridges and Canada Geese dominate the bird fauna in many lowland landscapes, at least in terms of biomass. The Rose-ringed Parakeet is increasing rapidly and its requirement for holes to nest in means that native hole-nesters may lose out as it continues to spread. Already, it is probably the bird species most often encountered by the inhabitants of our capital - whether they recognise its raucous call or not. Other non-native birds have either established a foothold in Britain, including Black Swan Cygnus atratus, Red-crested Pochard Netta rufina and Eagle Owl Bubo bubo, or are waiting in the wings for their chance, such as Sacred Ibis Threskiornis aethiopicus and House Crow Corvus splendens. Their potential impacts are uncertain but it is unrealistic to expect that they can all thrive here without increasingly significant adverse impacts on native wildlife. With limited resources we have no choice but to prioritise efforts to control non-natives and it seems sensible to concentrate on species that are recent introductions, have the potential for significant adverse impacts on native wildlife (or economic interests) and are well beyond their native range. I have little sympathy with the view that all control of non-native animals is unacceptable and I detect a certain amount of desperation in some of the arguments put forward to justify that position. Eradicating introduced species is not 'ethnic cleansing' as is sometimes suggested, any more than shooting a pigeon or swatting a wasp is 'murder'. Humans and other animals are not the same thing. If we allow the complexities of the arguments to get in the way of action, we risk sleepwalking into a gradual acceptance of more and more non-native species and a further eroding of our native wildlife. Not so much 'live and let live' as 'live and let die'. Ian Carter

Issue 3
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