Hello all,
The bird most probably has salmonella poisoning. It is not uncommon that
birds blow themselves up like that to keep warm when they have been
infected. The salmonella bacteria is easily spread from bird to bird, this
is why it is necessary to keep bird feeders and bird trays as clean as
possible.

All the best,
Eddie Chapman, Voss.  Norway.
http://www.birdwatching-in-norway.com
Personal Guiding; Scheduled and Custom Birding Tours - 
Photo Album: Great Grey Shrike.