Most people who love birds are content to occasionally fill their bird feeders and see whatever comes along.

Siberian Chiffchaff - photo courtesy London Wildlife Trust

Listen to the Chiffchaff bird song (.ogg file)

Other bird watchers devote hours of each day to keeping an eye out for birds, in the hope of a rare sighting.

Mark Pearson is in the second category. He's the community officer for London's Wildlife Trust, a charity that aims to protect London's wildlife and wildspaces for the future. Pearson was out walking the other day (in the East Reservoir Community Garden in Stoke Newington) when he spotted an unusual bird -- a Siberian Chiffchaff -- more than 3000 miles off its usual migratory path, or from its home habitat in Siberia, the answer to our Geo Quiz.

The Siberian Chiffchaff is one of the rarest species spotted in this area in a long time says Pearson, along with an Iceland Gull which was sighted last month. To confirm its identity, Pearson studied its plumage, took some good quality photos, and then managed to elicit the bird's contact call using his mobile phone. Have a listen to his story!

Siberian Chiffchaff - photo courtesy London Wildlife Trust