There are many constraints on reproduction for birds that are not resident or that migrate between fixed areas. Nomadic birds, often dependent on fairly short-lived resources, need to be adapted to being able to fairly rapidly find nest sites, build nests, lay eggs, raise young and move on together with the young once the food begins to run out. Elaborate, prolonged courtship displays can use up valuable time. Nevertheless, courtship displays in one family of birds in which there is a high proportion of nomads (the Alaudidae) vary among the nomadic species from intricate aerial manouvres with complicated songs to perch displays with monotonous songs, to quite simple ground displays with simple calls. Pre-breeding displays in Stark’s Lark Eremalauda starki and Grey-backed Sparrowlark Eremopterix verticalis may be quite synchronized, with hundreds of males calling and performing simultaneous aerial displays (Maclean 1970a, b; Willoughby 1971).