Chrisf mentioned some interesting facts about bird nests after finding one in his Christmas tree.   I tried to identify the white stuff in this untidy nest but it was too difficult to reach in the hawthorn hedge and looks as if it has been added since the nest was used for eggs.  Despite passing many hedges I saw only one other nest which consisted of a very messy mass of sticks being built by a magpie, and it made me wonder what happens to the old nests as it is uncommon to find more than one or two in the countryside yet often any in the garden seem to remain.     (The photo makes the white look pale blue)