I recently relocated a recording of the Siberian Chiffchaff on Brownstown Head in late March 2012 which was the first to be proven by DNA sampling (published in Collinson J.M., Shannon T., Archer P., Odin N., Riddington R. & Walsh P. 2013. Genetic analysis of migrant Siberian Chiffchaffs in Britain and Ireland. British Birds 106: 109-113. )
Anyway, a cleaned sample of the recording (made on the most rudimentary kit you could conceive...) is attached as well as a sonogram of the call
The sono shows the distinctive flat shape of the call compared to the steeply rising shape of a collybita call.
This is fantastic! Thanks for sharing, Paul.