Here's a new robotics term for you to memorize: multi-modal locomotion. It means locomoting in multi-modes, and that just means getting around in more than one different way. Most animals are multi-modal: they can walk and swim, or walk and fly. This isn't a coincidence, because there are clear advantages to being able to do move multi-modally, with capability and efficiency coming out near the top of the list. The disadvantage is that generally, you need a substantial amount of extra hardware for each mode of locomotion, but EPFL has managed to create a UAV that can use its wings to walk.
This robot takes advantage of "adaptive morphology," where you've got one structure (the wings, in this case) that can be used for multiple locomotion modes. In a search and rescue situation, you might use a capability like this to fly around and get a good overview of an area, and then land and crawl around under some bushes if you spot something interesting. Also, small UAVs tend to land, um, badly, and being able to move around (even just a little bit) vastly improves the potential for returning to the air successfully.
It's probably not possible to design wings that have much structural commonality with particularly efficient legs, but that's not a problem when you can just invent some wings that change their shape, which looks to be where this research is going next:
We aim to make adaptive deployable wings for improving the mobility of a flying robot; their shape could be adaptively modified to augment efficiency of forward flight, hover flight, and displacement on the ground. For example, wings could be fully deployed for flying outdoors and reduced for hover flight and ground modes.
[ EPFL ]