Although a lot of SEOs and Marketers are only hearing about Hummingbird for the first time this week, it has been running as the new "Engine" for around a month or so.
Google’s saying there’s nothing for SEOs or publishers worry about as there's no need for us to change what we're doing. Given that there hasn't been a marked shift in rankings over the last month (certainly not on the same scale as with Penguin, Panda or Caffeine updates were rolled out anyway), it's suggested that Hummingbird isn't something to fear.
From what I can gather, it is an added level of intelligence which has been plugged into Google Search in order to improve long tail search results and results for Conversational Search.
Anyway, I hope that my reply is helpful!
