Small drones can do big jobs: Firefighters can use them to find hot spots in blazes, environmental monitors can find the source of hazardous chemical leaks. One just delivered a human kidney for transplant surgery.
But it takes lots of power to spin four helicopter blades fast enough to keep a quadcopter-type drone in the air. Most can only stay aloft for about 30 minutes.
So an international team of roboticists is trying to extend the time a drone can stay on the job. For inspiration, they turned to birds.