While Hummingbird has been much discussed, not many people understand it yet, or appreciate its benefits because it isn't an obvious feature of Google search. If you want to try it, go to Google on your smartphone and click on the microphone to activate a voice search.
For a bit of fun, say 'Tottenham Hotspur'. Google will search for the greatest team in the world (guest opinion - Ed), and then read out an up to date fact, perhaps the latest result and information about the next match.
Next, click the microphone again and ask a related question, such as 'how old are they?' Google will then show you the Wikipedia information about the club. Ask another question, such as 'where do they play?' and Google will show you information about White Hart Lane.
So, that is Hummingbird in a nutshell - a clever way of linking queries so that, instead of starting each search from scratch, Google can show you more pertinent information related to your previous search.
Via Russ Merz, Ph.D.