1. An unmanned aerial vehicle comprising: a camera configured to generate photographic images; memory storing first travel instructions that define a first flight path for the unmanned aerial vehicle; memory storing one or more pre-defined image characteristics that correspond to one or more image characteristics that are exhibited by images of one or more pre-defined objects and/or one or more pre-defined objects having one or more pre-defined conditions; and one or more processors configured to: control flight of the unmanned aerial vehicle to perform a first part of the first flight path by executing some of the first travel instructions; control the camera to generate one or more photographic images with the camera while performing the first part of the first flight path; process the one or more photographic images generated by the camera during the first part of the first flight path to determine whether or not any of the one or more pre-defined image characteristics are present in the one or more photographic images; in response at least to detecting some or all of the pre-defined image characteristics in at least one of the one or more photographic images generated by the camera during the first part of the first flight path, generate and/or retrieve second travel instructions that define a second flight path for the unmanned aerial vehicle, the second travel instructions causing the unmanned aerial vehicle to travel toward one or more pre-defined objects or pre-defined conditions exhibiting some or all of the one or more first pre-defined image characteristics; after performing the first part of the first flight path, control flight of the unmanned aerial vehicle to perform the second flight path by executing the second travel instructions; control the camera to generate one or more photographic images while performing the second flight path, wherein the one or more photographic images generated during the second flight path include at least one image of a pre-defined object or pre-defined condition that corresponds to the pre-defined image characteristics detected in the at least one of the one or more photographic images generated by the camera during the first part of the first flight path; and perform a second part of the first flight path by executing some of the first travel instructions after performing the second flight path by executing the second travel instructions.