By Nick Higham
Stratford, east London
As part of his BBC Springwatch series on changing habitats in the UK, Nick Higham reports on efforts to build a green Olympics in 2012.
Pudding Mill River isn't much of a river, really: more a sluggish ditch a few hundred yards long, full of rubbish, disfigured by piles of old tyres, and overlooked by big sheds where London's demolition waste is noisily ground up to be recycled.
But Pudding Mill River is home to a family of swans on the water, and to pike and eel under it. It's typical of the semi-derelict urban wasteland lying all around our towns and cities.
Unsightly and unpromising though it may look, it's an important habitat for birds and animals. But now, the wildlife is under pressure from developers, anxious to turn old "brownfield" sites into profitable housing and office blocks, as London's population grows by 800,000 to eight million over the next 10 years.
Pudding Mill River will disappear soon - because it's part of one of the biggest and best-known development sites in Britain. By 2012, there'll be a spanking new Olympic stadium here, and all around will be a vast landscaped park.
The Olympic Delivery Authority (ODA) is taking its responsibilities towards the local wildlife seriously. It's surveyed what's there, and where possible it's transferring it to new homes.
These fish will be alright - but what about other wildlife elsewhere?
The fish in Pudding Mill River have been briefly stunned by electric current, and "translocated" to the nearby River Lea.
Artificial nests are being built for displaced kingfishers and sand martins. And no fewer than 700 smooth newts living around a pond on the Olympic site (plus 120 toads) have been moved to a new pond at a nearby nature reserve, The Waterworks, developed on old Thames Water filter beds.
When we tried to find the newts at their new location it took us half an hour to turn up a solitary male. Simon Wightman from The Waterworks reckoned their elusiveness showed they were instantly at home - though it could, I suppose, mean they hated it and had promptly legged it.
Some birds and animals aren't so easy to deal with, though.
The black redstart used to be common in London - it's a bird that likes broken ground and hard, stony surfaces and it flourished after World War II on bomb sites. But the bomb sites have gone and so has the black redstart: it's now extremely rare.
The black redstart is among the UK's rarest birds
Ecologists believe a few pairs have made the future Olympic site their home, and redevelopment could drive them from one of their last redoubts; the best the ODA can do is provide some stony areas in the new landscaped park and hope the black redstart takes to them.
Not all developers are as responsible as the ODA.
For most, the local wildlife may be little more than a nuisance. And green organisations like the Royal Society for the Protection of Birds fear all the attention and money devoted to the Olympics may divert attention from the plight of species deprived of their habitats elsewhere - especially in the vast regeneration zone known as the Thames Gateway.
The BBC's Springwatch Season 2007 begins next Monday, 28 May, on BBC Two, and runs for three weeks. Bill Oddie, Kate Humble and Simon King will be reporting from across the UK on British wildlife.
Do you have a question you would like to put to Springwatch presenters Bill Oddie and Kate Humble?