I believe this bird may be made by a Lithuanian company called Svaja who make several different styles of glass.
Their first birds to be produced were in the Sommerso style, but now are a more simple coloured combination, so it is difficult to find an example to prove this. They have a website:
http://www.e-svaja.com/ who may be able to confirm this if you write to their address, which coincidentally is in Surry, 5 minutes from where I used to live! (Before I started to collect glass!)
I hope this is useful, and you can see the range if glass they produce, including many pieces which do appear to be Sommerso technique.