Crossbills over Griston, Norfolk 02/07/13.

4 Crossbills seen very high overhead (from the north-east) at Griston, Norfolk at about 1130 on 02/07/13.  Had these birds not been calling I may have overlooked them, the call is a highly distinctive "chip-chip" note.
Crossbills do breed in small numbers in Breckland; their breeding season starts early in the year around January and February.  In some years large irruptive flocks of Crossbills move into Britain from Northern Europe, the reason for these movements usually coincides with a failed or an insufficient supply of food, this being the seeds of pine cones such as those found in the Larch. These irruptive movements of Crossbills generally starts in May and may continue through to the autumn.
My observation of these Crossbills along with their directional approach suggests these may well be irruptive birds from Northern Europe, it would therefore be interesting to see if other birders have noticed similar movements.