Friday was a black day. We lost an eight-week-old female peregrine.

Peregrines at play in mid-air, photo kindly supplied by David ShawThese magnificent birds have taken to London in a big way. We now have half a dozen breeding pairs living wild in the Capital and probably double that in single birds - not yet at breeding age.

The female was found on Thursday last week, badly injured on the ground in London Wall near the Museum of London. She was taken by one of our volunteer peregrine experts to London Zoo for treatment but they decided she'd have to go to the Hawk Conservancy Trust in Andover for specialized care. X-rays showed a fractured hip but her back was badly dislocated and survival was not possible.

This was the only daughter of Misty and Bert, the peregrines that usually roost on the Tate chimney. They had four chicks this year; three males and the female. They don't appear to be registering her loss and are not searching for her. At eight-weeks, the female had learnt how to fly, hunt and generally look after herself.

The area around London Wall has a lot of glass and steel structures and it's entirely possible that she collided with one of these. It seems the Capital is not as welcoming and safe a place as we had thought for peregrines. It is warmer than the surrounding countryside and with its large pigeon population, resembles a well-stocked larder for a hungry peregrine.

Glass buildings and birds are not a great mix. Another young peregrine was found dead last year. It too had collided with something. There are well documented cases of birds flying in to glass buildings, but it's not a major problem and is more common in US and Canadian cities where there are more high rise buildings. Peregrines are the fastest creatures on this planet. It must be tough, even with their powerful eyesight, to detect glass structures, especially if they're diving at top speed (more than 100 mph). Accidents happen and it's a sad loss.

I was telling a journalist friend the story of the juvenile peregrine. They didn't appear to register any reaction and when I'd finished they said "So what?" I'd be the first to admit that the loss of a single wild bird cannot compare with the loss of a child, a parent, a colleague or friend. It's just sad when any young life ends abruptly and this was the young life of a species that came close to extinction. Happily, she wasn't the last of her type. However, if you look at the statistics in London, we're seeing more male peregrines than females. If that trend continues, extinction remains a real threat!

So, take advantage of these magnificent birds being in London by visiting us at the Tate this July. Repairs to the storm-damaged lightbox on top of the Tate Modern's chimney are running on longer than planned. It will soon be fixed, but with work teams around, the peregrines are unlikely to use the Tate roost as they normally would. It seems our Tate Peregrine Watch may start on July 19 without the regular presence of the birds. As soon as the people on the chimney have finished and gone, we're expecting the peregrines to return. We'll be there as planned, so come and see us to find out more about Birds of Prey in London.