My research concerns the energetics and control of bird flight. To explore questions within these themes, I focus on two systems - dynamic soaring flight in Procellariiformes (the albatrosses, petrels and shearwaters), and pursuit of targets by birds of prey. Dynamic soaring is a flight mode that enables the harvesting of energy from wind gradients. Procellariiformes can fly thousands of kilometres at reduced biomechanical energy demands by virtue of performing dynamic soaring. Using data from on-board video cameras and GPS loggers, I investigate how optimally Procellariformes harvest energy from the vertical wind gradient above the ocean surface, how they respond to varying wind conditions, and the implications of dynamic soaring for their large-scale distribution. To answer these questions, I have developed new theory on the energetics of dynamic soaring, and a new horizon detection algorithm for the modelling of flight trajectories from on-board video camera data. Falcons and hawks guide themselves to prey targets with extreme precision. I use algorithms taken from the literature on homing missile guidance to model target pursuit by Harris' Hawks. By assessing the fit of different guidance laws to pursuit trajectories, I can obtain phenomenological models of bird guidance. The properties of the best fitting phenomenological models then imply the required sensing requirements for Harris' Hawks in their pursuit of targets. I test these through high sampling rate recordings of bird eye and head motion, and experimental manipulations of the visual scene of birds engaged in pursuit. I am also interested in questions within the field of phylogeography and, to this end, have engaged in research expeditions to collect, describe and sequence putative new species. I am currently organising an expedition to the Cyclops Mountains of Indonesian New Guinea for this purpose.