Cutsey blue tit - not afraid of the Grenadier Guards and constantly breaches security by flying over the walls.Our office is in central London and we look out on to a building site at the back and, at the front the imposing concrete bulk of Wellington barracks; presently home of the Grenadier Guards.

It's not the sort of place you'd expect much biodiversity. This year, we've recorded a leap forward. Not only do we have blue tits and great tits nesting in the tree-lined street at the front, we've breeding blackbirds in an unpromising light-well at the rear of the building.

The tenants in the basement recently came to report what appeared to be a bird in distress in this light-well. It turned out to be a baby blackbird that had tumbled from its nest. Mum and Dad were nearby and delivering food so we reassured the staff that the bird was well and best left alone. Happy with this information, they were then free to relax, watch and enjoy the drama of a young bird's first few days and weeks of life out of the nest.

We humans seem to have a pre-programmed desire to intervene. We see small birds or animals and want to "do something" about them. It's the same with plants. We take cuttings or seeds to grow our own or, at the other end of the scale, we name them weeds and try to wipe them out of existence.

Some kind soul, unable to look after their goldfish, dumped them in ponds in Islington's Gillespie Park. The fish have spawned and done well, but sadly the mix of dragonflies the pond was managed to support has not only dwindled in population, but some dragonfly species have been gobbled out of existence! That's an act of ignorance but shows how every act must be thought through.

Male black redstart - see its red tail feathers?The truth is, we humans rarely leave anything to run truly wild and unmanaged. Mind you, without the mosaic of habitats that surround us, we wouldn't have the huge range of plants and creatures to watch and enjoy, particularly in London. Where else could you have chalk grassland next to reedbeds, or salty mudflats supporting redshank alongside scrubby brownfield sites favoured by black redstarts.

Getting the balance right between conserving this great mix of places and species or over-managing a site in favour of a threatened species to the detriment of others, is never easy. Only history can really show whether correct choices are made.

History shows that humankind's curent priorities never outlast the environmental priorities. That's a good reason for demanding MP's change the Marine Bill to put environmental priorities over socio-economic ones. This is one of the many campaign's where the RSPB is speaking up for nature. It's also a great opportunity for MP's to go down in history for doing the right thing rather than being remembered for their expense claims.