From IEEE Spectrum
Here's a quadrotor with giant spindly bird legs from the Utah Telerobotics Lab. It's a passive system which uses the weight of the robot to actuate the grippers, so that when the quadrotor lands on something it latches on and stays. To release, the robot just lifts off, and the grippers let go. Birds use a very similar system to keep themselves perched while asleep, and the leg and toe design was inspired directly by songbirds.
Here's it flying: