When the Spanish arrived, the Aztecs had sophisticated agricultural techniques and an abundance of food, which was the base of their economy. It allowed them to expand an empire, bringing in tribute which consisted mostly of foods the Aztecs could not grow themselves. According to Bernardino de Sahagún, the Nahua peoples of central Mexico ate corn, beans, turkey, fish, small game, insects and a wide variety of fruits, vegetables, pulses, seeds, tubers, wild mushrooms, plants and herbs that they collected or cultivated.