Curtius, History of Alexander the Great 4.8.6
Alexander is in Egypt, founding Alexandria:
fama est, cum rex orbem futuris muris polenta – ut Macedonum mos est – destinasset, avium greges advolasse et polenta esse pastas; cumque id omen pro tristi a plerisque esset acceptum, respondisse vates, magnam illam urbem advenarum frequentiam culturam multisque eam terris alimenta praebituram.
The story goes that, when the king had marked out the circle of the future walls with barley (as is the Macedonians’ custom), a flock of birds flew up and ate the barley. Although this had been interpreted by most people as an ill omen, a priest responded by saying that a host of foreigners would inhabit that great city, and that it would provide many lands with food.