New species of bird

This new bird species was recently discovered at my garden feeder on 10/05/14.  It is quite cunning as it repels attacks from Sparrowhawks by retracting into a shell that it carries on its back. Unfortunately, this is no defence to the Song Thrush who has learnt to smash it on a stone used like an anvil. It is quite slimy and seems to have an aversion to salt. Its biggest predator threat comes from people from France.

Species name - slimeball