**1. Introduction**

Nocturnal birds of prey birds have long been considered as a "unit" in several classifications of animals [1, 2]. Currently, they are classified in the order Strigiformes, within a larger group called the "African landbird radiation" that includes the orders Cathartiformes, Accipitriformes, Trogoniformes, Coraciiformes, Piciformes, among others [3]. The Strigiformes are difficult to study because they occur in low densities, have generally elusive behaviors, most are strictly nocturnal, and usually remained overlooked [4]. Although research on Strigiformes biology has intensified over the last few decades [2], many owl species remain little studied.

Knowledge about the feeding ecology of Strigiformes, including which organisms are preyed upon them, is a key for understanding their role within a given ecosystem, and even elucidating whether they can be beneficial for human health. However, witnessing owl predation events in the wild is unusual, so analyses of owl pellets become the most effective method for studying their diets. Owls usually swallow their prey whole or in large pieces, and then regurgitate a pellet containing indigestible matter, such as bones, fur, feathers, and other keratinous material, about once a day [5]. Owl pellets are also an efficient alternative for measuring small mammal community composition [6].

Ecuador is home to 29 out of 45 South American species of Strigiformes [7]. For the majority of owls occurring in Ecuador, scarce information about their natural history exists, including their feeding ecology [8]. As there are few reviews of the diet of Neotropical owls at country scales [9, 10], in this chapter, we present a revision of information on the diet of owls in Ecuador. Further, we present some guidelines for the study of owls' diets and highlight topics that could be investigated. Our aim is to promote further scientific research about the feeding ecology of nocturnal birds of prey.
