London's city wildlife, and what buildings can do for it
I studied zoology at Bangor and then spent eight years at Battersea Dogs and Cats Home before I ever worked on a building. So I still notice animals first. London is full of them, and a surprising number depend on the buildings I now spend my days modelling.
The ones everyone sees
Foxes
Foxes are the obvious London success story. Gardens, railway embankments, allotments and bins give them food and cover, and they've got very good at living right next to us. Most Londoners have stories about one walking down the middle of the street at 2am as if it owns the place. In a sense it does.
Parakeets
If you'd told someone in the 1970s that bright green parrots would become a normal sight in London parks, they'd have laughed. Now they're everywhere, especially in the south and west of the city.
You've probably heard they came from Jimi Hendrix releasing a pair on Carnaby Street, or escaped from the set of The African Queen. A 2019 study led by Queen Mary University of London looked properly at the records and found no evidence for either story. The population most likely built up from lots of separate pet escapes and releases over many years.1 Less romantic, but more believable.
Peregrines
Peregrine falcons are one of my favourite city birds. To a peregrine, a tall building is just a cliff, and London's pigeons are an endless food supply. The London Peregrine Partnership has been supporting them since 2003, when the first pair tried to breed in central London.2 They now nest on towers, churches and power stations across the city. If you hear a sharp, harsh call above a tall building, look up.
The ones that need help
Swifts
Swifts are remarkable. They spend almost their whole lives in the air, eating, drinking and even sleeping on the wing. They only land to nest, and in Britain they nest almost entirely in buildings, usually tucked into small gaps under eaves and roof tiles.
That's exactly where the problem is. When old buildings are refurbished, those gaps get sealed. According to the British Trust for Ornithology, UK swift numbers fell by 70% between 1995 and 2024, and the species has been red listed since 2021.3
Bats
London has several bat species roosting in roofs, walls, bridges and trees. All UK bat species and their roosts are protected by law, which is why bat surveys come up so often before building work and demolition.4 They can feel like a hassle on a project programme, but there's a good reason for them.
Hedgehogs
Hedgehogs are an interesting one, because the news isn't all bad in cities. The State of Britain's Hedgehogs 2022 report found rural hedgehogs had fallen by somewhere between 30% and 75% since 2000. Urban numbers, on the other hand, appear to have levelled off and may be starting to recover, although from a low base.5
The biggest problem for city hedgehogs is fences. A hedgehog can travel a long way in a night looking for food and mates. Solid fences and walls between gardens cut them off.
Where my two worlds collide
A lot of energy work is about sealing buildings up: better airtightness, more insulation, closing gaps. That's the right thing for energy and carbon. It's also exactly how swifts and bats lose their homes.
The good news is that the fixes are small and cheap, as long as someone thinks about them at design stage rather than after the scaffolding comes down:
- Swift bricks. Hollow bricks with an entrance hole, built into the wall. They sit outside the insulation line, so they don't compromise the thermal envelope.
- Bat boxes and bat access tiles, fitted on the outside of the building or into the roof.
- Green and brown roofs. Good for insects and birds, and they also help with rainwater and cooling the top floor in summer.
- Hedgehog highways. A gap about 13cm by 13cm at the bottom of a fence is enough.6
Biodiversity net gain
Since 12 February 2024, most major developments in England have had to deliver at least a 10% gain in biodiversity compared with what was on the site before. Smaller sites followed in April 2024.7
I think it's a good push in the right direction. My worry is that it can become a numbers exercise done by a separate consultant once the design is fixed. The best results come when ecology sits in the same room as the energy and design team from the start. Then you can put a swift brick in a wall that's being rebuilt anyway, instead of trying to bolt something on at the end.
Look up
Next time you're walking around London, look at the rooftops, ledges, railway banks and old brickwork. There's far more living up there than most people realise.
References
- Queen Mary University of London, Parakeet "crime map" busts Bogart and Hendrix myths, 2019. Study published in the Journal of Zoology.
- London Peregrine Partnership, About us.
- British Trust for Ornithology, Swift BirdFacts.
- GOV.UK, Bats: protection and licences.
- National Biodiversity Network, The State of Britain's Hedgehogs 2022, report by PTES and the British Hedgehog Preservation Society.
- Hedgehog Street, PTES and BHPS.
- Herrington Carmichael, Mandatory biodiversity net gain changes from 12 February 2024.