Dr Martin's book is an investigation of the complex relationship between nocturnal birds and the particular environment that they inhabit from dusk to dawn. The survey covers not only the activities of owls and other nocturnal birds but also species which are only occasionally nocturnal, together with those which are primarily diurnal in habit. The special case of cave dwelling birds is also considered. The study of nocturnality in birds encompasses field ornithology, sensory science, ecology and physics, and involves comparisons of the sensory capacities of other animal species, including man, to respond to the night world. In weaving together the relevance of these various disciplines the author achieves an insight into the sensory problems posed by a nocturnal life style and the strategies and specialization which have evolved in response.