Nomadic birds track resources that are, in the general sense, nomadic in time and space. Ephemeral plants in desert ecosystems that emerge, grow fast and produce large quantities of seeds after irregular rainfall events are, in effect, nomads in time. So are other potential foods, including outbreaks of rodents (Wilson 1970; Hollands 1979; Windberg 1998; Lima and Jaksic 1999; Lima et al. 1999; Perrin and Boyer 2000), breeding colonies of Wattled Starlings Creaophora cinerea (Liversidge 1961), Red-billed Queleas Quelea quelea (Ward 1965), stick insects (Phasmatidae) (Readshaw 1965), dragonflies (Odonata, Anisoptera) (Rudolph and Fisher 1993),noctuid moths, grasshoppers and locusts (Dingle 1996). Although there is some predictability in the movements of Red-billed Queleas, breeding colonies are seldom in the same place twice. The colonies provide food for larger nomadic birds such as Tawny Eagles Aquila rapax (Biggs 2001) and Lesser Spotted Eagles A. pomarina (Pienaar 1969; Kemp 2001).