Flocks of wild parakeets with a taste for horse chestnut trees could have a knock-on effect on Northamptonshire's annual world conker championships.
Parakeets, pictured by Mark Jobling, are spreading across the south
Ashton Conker Club warns conkers may be in short supply for its contest on 9 October because the birds are chewing up the trees in the south of England.
Under club rules only conkers from Ashton can be used and they are worried that they may also come under attack.
Last year some 5,000 people watched 300 competitors vie for the conker title.
John Hadman, of Ashton Conker Club, said: "Flocks of parakeets are chewing up trees, including conker trees.
"We are keeping an eye on the situation and if they spread further than Watford we will have to take some sort of measure."
Colonies of up to 10,000 parakeets have been reported in West London, Surrey and Kent.
These small vivid green parrots, which originate in northern India and first appeared widely in the 1970s, are thought to have established themselves from private collection escapees.
According to a recent scientific survey their numbers are now rising at a rate of 30% a year in England.
Alternative to fishing
This is not the first time the conker contest has been under threat. Last year leaf-mining moths were found to be feasting on horse chestnut tree leaves in Europe and the UK.
Two years ago the conkers fell too early for the championships and organisers had to put in urgent requests for conkers from other parts of the country.
The conker championships date back to 1965 when a small group of pub regulars decided to play conkers as an alternative to fishing because of bad weather
Competitors go armed with a conker on a 12-inch string. They play on 10 white podiums on the village green and go through rounds until the winner emerges and is led to the Conker Throne and crowned with conkers.