**1. Introduction**

Most owl species have nocturnal or crepuscular habits, and due to darkness, owl communication relies greatly on vocal activity. In temperate regions, it is the owls

which in late winter or early spring fill the night with music, and in the tropics, owls are just part of a formidable chorus of animal songs and calls. Calls are completely diagnostic of species, and owls are likely to recognize other individuals by voice as by sight during their travels in the dark [1, 2]. Every vocalization in an owl's vocabulary has a precise meaning in the communication with conspecifics. Calling is advertising their presence, to locate and attract potential mates, and to establish or to reaffirm breeding territories [3].

In Africa, some owls call almost daily at sunset or soon thereafter, and others are vocal in the still hours before dawn. Often their calling bouts are only momentary and fragmentary, but sometimes, especially just before breeding, they are loud, complex, and prolonged, extending almost throughout the night [4]. Calling at dusk may be mandatory—at least in species that reside in their territories throughout the year—as a notification to neighbors that the owners are still in residence. Later calling may be timed to take advantage of good conditions for sound transmission, or it is a response to social pressure such as neighbors calling, intruders present in the territory, or prospective mates being noticed [4].

The chapter tries to tackle the following questions: (a) What are the main factors influencing the temporal patterns (daily and seasonal) of vocal behavior of African owls; (b) how some environmental variables, like moon, wind, and rain, will influence the calls for some species, and (c) if and how useful vocal records are in surveying the distribution and population size of the different owls. At the same time, this chapter will also give some anecdotes collected on the human nightlife and the nocturnal behavior of some domestic animals and wildlife near the house.

Nowadays, it starts to be outdated and old fashion to collect vocal activities of any owls just by listening and writing down the results as the use of automated bird presence recognition is becoming the modern method for wildlife monitoring. It is felt to be more beneficial for avian biodiversity conservation [5].

This could be the last opportunity to put on record these old African owl call studies from Malawi and The Gambia between 1993 and 2004.
