Discrete animal-mounted sensors and tags have a wide range of potential applications for researching wild animals and their environments. The devices could be used to monitor location, metabolic output, or used as environmental monitoring sentinels. These applications are made possible by recent decreases in the size, mass, and power consumption of modern microelectronics. Despite these performance increases, for extended deployments these systems need to generate power in-situ. In this work, we explore a device that was recently deployed to test the concept of vibrational piezoelectric energy harvesting on flying birds. We explain the development of the device and introduce test results conducted on flying pigeons (Columba livia). The 12 g testing device consisted of a miniature data acquisition system and a piezoelectric energy harvester. The system recorded both the harvested power and the in-flight accelerations of the bird. The energy harvester included a wireless receiver, battery and linear servo. By remotely actuating the linear servo, we were able to arrest the energy harvester for portions of the flight. In doing so, we will be able to compare flight accelerations of a bird with a simple proof mass and with a dynamic mass without having to stop the flight of the bird. The comparison of these two cases allows for the assessment of the feasibility of employing vibrational energy harvesting on a flying bird. We present the initial results of this testing with regard to the harvested power and the in-flight acceleration profiles.