Today,20th April, magpie chattering happily in tree where nest was built. This tree already full of flowering leaves and nest almost invisible. There are two  adjacent trees(one taller-different species of tree) but both very bare of leaves so nest site would be fully exposed if built in either one of these.

Did the magpie know its chosen tree would flower earlier,(and hence conceal its nest)?

Probably, as its well equipped for modern life, as are all crow species(except the chough)!!