Sociable Weaver (Philetairus socius)
As their name suggests, these birds nest and brood in groups. They build a gigantic nest-within-a-nest structure attached to trees and poles. A compound nest can house over 100 breeding pairs, each contributing to its construction, maintenance and repair. Living in groups means someone is always on the lookout for danger.
Many More:
http://www.bbc.com/earth/story/20150307-the-16-most-amazing-bird-nests
