Do swarms show intelligence?
Intelligence is something which has to have a definition, and there are many, but I would cautiously say no. 

The reason that I say this is because swarming behavior can be largely reproduced by a simple set of rules - matching distance to your neighbors and direction and speed as well.  To me this really removes any intention or even conscious element to swarm behavior although its clear individuals do make decisions, they don't have to be more intelligent than a mouse looking for food or other kinds of animal behavior.  

That being said, others have literally built definitions of intelligence inspired by swarming - a decentralized sort of mind which makes decisions based on the interactions of component individuals.  You could argue that our own brains are a similar sort of ensemble, and therefore no more different than our own intelligence if we look closely enough.

So take your pick really.