With the advent of the Islam and the colonial era, slaves became a valuable resource for trading with European, Arab, and Chinese slavers, and the volume of piracy and slave raids increased significantly. Numerous native peoples engaged in sea raiding, they include the Iranun and Balanguingui slavers of Sulu, the Iban headhunters of Borneo, the Bugis sailors of South Sulawesi, and the Malays of western Southeast Asia. Piracy was also practiced by foreign seafarers on a smaller scale, including Chinese, Japanese, and European traders, renegades, and outlaws. The volume of piracy and raids were often dependent on the ebb and flow of trade and monsoons, with pirate season (known colloquially as the "Pirate Wind") starting from August to September.