There are different approaches to flight, fixed wing, quad copter, etc., including flight by using the same principles that a bird or insect uses to fly.
The concept is not new, Leonardo da Vinci drafted up a concept of bird in flight for human flight. There have been toys such as the french made and designed flying bird that many of us flew as children, and there are more sophisticated drones that are used to emulate the flight of birds.
Several companies have created drones that fly like Hummingbirds.
It has been said that the Chinese have developed these type of birds for reconnaissance, which makes sense as when you see some of these drones in flight it does not draw your attention in the way that traditional quad-copter does.
This was covered in a TED talk in Amsterdam in late 2016, that speaks to all type of machines that emulate animals, birds, an insects including drones. The flying part starts at the 2:00 minute mark if you are pressed for time.
Another example is the Fesco Smartbird, which really has a striking resemblance to a bird in flight which is also shown in the TED talk above with it’s wing pattern shown below. The drone was inspired by the flight and appearance of a herring gull. The ultralight flying model has outstanding aerodynamics and agility and is able to take off, fly and land without an additional drive.
As drone usage becomes increasing mainstream, we look to see more of this type of drone that seeks to blend into the existing environment.