BILL NAYLOR says it’s time to stop stigmatising ‘alien’ bird species
THE several pairs of eagle owls living in the UK, some of which have bred, have recently been the subject of a risk assessment by DEFRA. The conclusion was that while there are no immediate plans to cull them, they should be managed. Many, however, interpret this to mean that a future cull cannot be ruled out.
Unlike most non-native species established in the UK, the eagle owl is native to Europe and was once native to Britain, though it died out here some 9,000 years ago. This is disputed by some owl experts, who believe it has colonised Britain more recently. Since eagle owls have been kept in captivity since the 17th century and have regularly escaped, the British Ornithologists’ Union (BOU) does not admit the species to its official list of British birds.
Although the RSPB has said it would not support a cull of eagle owls, it has recently voiced concerns that these fierce predators could put the fragile UK population of hen harriers under threat.
In the UK, eagle owls feed mainly on rabbits, and elsewhere their usual prey is rats and lemmings, but they are capable of taking small deer, which prompted the RSPB also to warn that pet dogs may also be in danger. Yet almost in the same breath, the society said that if eagle owls - which are expanding their range in Europe – do invade Britain naturally, they will be most welcome.
Aliens around the world
Although invasive species are said to be the greatest threat to native bird populations around the world except for habitat loss, they are a distant second – 60 million new humans every year see to that. In fact, very few non-native species are genuinely invasive, and by calling them “aliens” the perception created is that if we eradicated them we would have a better environment. That is nonsense – we would create new problems and there isn’t a nature reserve in the world free from non-native species.
While introductions of rats, foxes, cats, and stoats into other ecosystems have decimated animal and bird-life, non-native species can also be beneficial. Indigenous birds worldwide nest in non-native foliage and eat non-native seeds, berries, rodents and other animals. Many raptors eat a high proportion of non-native animals and birds. Peregrines have been seen hunting ring-necked parakeets in London.
Some introduced species such as little owls and Mandarin ducks have integrated seamlessly in the UK. However, even the transfer of apparently harmless species from one ecosystem to another is a big gamble, because they don’t always behave as they do back home. Pekin robins and zosterops in their own habitats are benign, but after being introduced Into Hawaii they proved serious pests of cultivated fruits. Blackbirds, song thrushes, skylarks, yellowhammers and goldfinches have all been categorised as pest species in their adopted countries, notably New Zealand.
The opposite can also happen. Quaker parakeets are major agricultural pests in South America, yet not in the UK. Ring-necked parakeets also a serious agricultural pest in Asia and Africa, but apart from isolated incidents they have not caused the damage widely predicted in the UK, (although one raid on a winery in the South of England is referred to in the press so frequently that it might appear that it is occurring regularly.)
Ruddy ducks and the RSPB
Monitoring invasive species and managing their impact on the environment is a obligation of all countries, and when a decision to cull is made it puts conservation organisations in a dilemma. The RSPB invited criticism and lost members when it endorsed the ruddy duck cull. For centuries Britain traditionally culled birds and other wildlife, with bounties paid by parish councils, church and landowners. The RSPB, formed to protect birds, was now backing a cull.
Ruddy ducks escaped from Slimbridge in the 1950s and spread across 13 European countries. Waterfowl hybridise more than any other group of birds. The Canada goose (one of the few 29 feral UK bird species that has proved to be invasive) was introduced here in the 17th century, and has hybridised with barnacle and greylag geese.
Introduced mallards in Australia and America, hybridising with their native black ducks (Anas superciliosa and A. rubripes), and in New Zealand with the native grey duck (A. s. Ssperciliosa), threaten the purity of those species. When ruddy ducks started to hybridise with white-headed ducks (Oxyura leucocephala) in Spain, a repeat of the mallard situation was feared, and in 2005 DEFRA instigated a cull of ruddy ducks, with the aim of stemming the species’ expansion from Britain to the Continent, including Spain. The cull is due to finish in March this year, and has cost more than £4 million.
Has the cull been justified? One highly qualified figure says not. The British ornithologist Tom Gullick, who is resident in Spain, was the first to alert the Spanish authorities to the serious decline in that country’s population of native white-headed duck. He was then instrumental in rebuilding their numbers, after they had declined to no more than 20-30 birds. Gullick called the cull an expensive unnecessary massacre. He believes hybridisation was rare, and is no threat to the purity of the species. The populations of ruddy ducks have since increased in several European countries. Opinion is sharply divided on whether the cull contributed to this.
What is natural?
Most habitat is not “natural”. It has been irreversibly altered by man and a changing world coerces populations of birds to change their habitats. Yet the phrase “naturally occurring” is frequently used.
Where conservationists do turn a blind eye to naturally occurring species is regarding reintroduced species such as red kites, capercaillie, white-tailed eagles and, more recently, great bustards and common cranes. These all originate from captive non-native individuals (a fact not always acknowledged) and adhere to a man-made ruling that if your species was in Britain in the Neolithic period, foreign birds of the same species have a right to residency.
Along with the introduced Mandarin, Carolina and ruddy ducks, plus Egyptian geese, peafowl, golden, Reeves’s and Lady Amherst pheasants, the most high-profile non-native UK avians are parrots.
These are the birds that make conservationists grit their teeth and growl. Alexandrine parakeets live in London and Kent. In 2004 lovebirds bred in Scotland. Quaker parakeets have lived here since the 1930s.
Ring-necked parakeets are the most plentiful UK parrot, with estimates of 50,000 quoted. In April 2010, however, the UK Imperial College Parakeet Project estimated the national population at about 19,000.
Ring-necks are said to compete with native hole-nesting species, but in fact they nest early in the year before our native birds go to nest.3 The accusation that they scare other birds has not been borne out either.
A cull of ring-necks rumoured to take place in 2010 never happened. However, their protection, and that of Quaker parakeets and Canada geese, has been relaxed. Whereas previously a special licence had to be obtained to control these birds, as of January 2010 only a general licence is required.
This was criticised by animal welfare groups and the London Wildlife Trust, who said that confusable species such as green woodpeckers could be in danger. They believed that no change in the law was necessary.
The public response to the ruddy duck cull, and rumours of other culls involving ring-necks and eagle owls, demonstrates that non-native birds, while seen as out of place by the hardline conservationists, are valued by sections of the community. And as demonstrated with feral parrots in the USA, the public may in the future determine how such species are managed.
2. S. Budiansky, New Science of Nature Management, The Free Press (1995)
3. C. Lever, The Naturalised Animals of Britain and Ireland, New Holland, London (2009)
Ornithologist and aviculturist Bill Naylor has worked in many zoos and bird parks in the UK and abroad.