Marloes etc..

1 female Marsh Harrier at the Mere.
The Gann, 2 adult Meds - one green ringed. 200+ Jackdaws, 4 Lapwing.
Monkhaven watertreatment, 1 Grey Wagtail.
On my Sojourn around the area, I came upon what appeared to be Rooks building or rebuilding their nests. Would they be keeping the rookery ready for the new breeding season (which to them is just around the corner) or something else?