I also fondly remember early May rook shoots (generally around the 7th-9th of that month) in Norfolk where my .22 air rifle was the weapon of choice. The meat from the young rooks or "branchers" was superb and a cross between beef and chicken.

I think the nursery rhyme "4 and 20 blackbirds" is actually referencing rook pie if memory serves, and the shoots were a way of traditionally managing the populations of local rookeries.