Rob goes to the local common (aka The Dump) and finds a jackdaw chick there.

He takes Joe the Jackdaw home, and keeps him as a pet.

Well, he couldn't leave him to die, could he? He causes no end of mess in the house, and then he starts flying into other houses in the street and stealing shiny things from them.

The ultimatum comes. Joe must go and live somewhere else. A long way away. But then, Joe discovers green glass. Lots of it. And, it's Anglo-Saxon! The campaign to save the common is finally going to work, and it's all thanks to the jackdaw!