In this work, we consider collaborative stereo-vision as a mean of localization for a fleet of micro-air vehicles (MAV) equipped with monocular cameras, inertial measurement units and sonar sensors. A sensor fusion scheme using an extended Kalman filter is designed to estimate the positions and orientations of all the vehicles from these distributed measurements. The estimation is completed by a formation control to maximize the overlapping fields of view of the vehicles. Experimental tests for the complete perception and control loop have been performed on multiple MAVs with centralized processing on a ROS ground station.