London peregrines at the Tate

Monday, 30 June 2008 9.58

Ringing success

Posted by Tim Webb

Twenty four birds successfully netted, one escapee. The London House Sparrow Research Project has been running for a couple of years now, and this week I joined two of the team as they weighed, measured and ringed sparrows in Islington.

Without taking any ages in to account I can reveal that the average weight of the sparrows was equal to that of a two-pound coin and a one-pound coin combined. Average wing length was about that of my index finger (7.5 cm) and the average tarsus, 2.5 cm or the same as the width of my thumb knuckle. Of course these averages are a bit of a nonsense because our sample included tiny juveniles and older males and females, but it is quite a low weight.

Netting is not selective so we also measured and weighed two blackbirds, two great tits, one lovely little robin and a starling. A typical selection of the species found on the site, a small park in Islington's Laycock Street. We were of course, primarily interested in sparrows.

The research project is trying to find out why sparrows are vanishing from London. Their numbers have dropped dramatically compared with the populations recorded in the 90's. No disease has been found to account for the losses and even when predation by cats and birds of prey are taken in to account, the speed and depth of the decline suggests something else is to blame. We know that a lack of food and shelter have had an impact so studies continue to look at other possibilities while supplying both food and shelter for some colonies.

House sparrow numbers reached an artificial high in the UK when our streets were full of horses chomping on oats and doing what horses do when their stomachs are full! When the internal combustion engine put horses out-to-retirement, house sparrow numbers started to drop to a more natural level. That was expected, but the decline we're concerned with is more sudden and recent. At present, it remains a mystery, but we're determined to crack it.

Sticking with red-listed birds. Last week we lost one of this year's new batch of peregrines. The female had to be put-down after badly injuring herself in a collision. Since then I've been finding out just how many peregrines hatched in Greater London this year. We had a nice round-figure of ten chicks from our six breeding pairs. It seems this is one threatened species  that is on the long, slow road to recovery.

We've been having a lot of calls to the London Office from people who've found young birds unable to fly. Rest assured these are youngsters and that they have a higher chance of surviving if left alone than they do if you intervene. The parents will be nearby and can help if required, so please resist temptation, enjoy the encounter and move on. If you want to know any more about the work of the RSPB and some of the amazing wildlife sharing our Capital city, come and find us on Hampstead Heath this Friday and Sunday.