Abstract: The appearances of the morphological variation, especially body sizes and wattle characters of Hill Mynah population found in Thailand bring the questions if Hill Mynahs use these variations for survival through the communication in order to determine status signals within flocks and which character is the most propagated. The study was conducted both in the aviaries and in the field. The experiments in the aviaries revealed that they used body sizes and wattle characters including aggressive behavior to communicate in order to determine social status in flocks in captivity. The bigger birds were always dominant ones and gained more food. The observation in the field did not show that the bigger birds mated more than the others, but it depended on the population density of each group which inhabited in particular areas. Although the results did not indicated the specific character that propagated most, the body size and wattle variations in Hill Mynah which corresponded with aggressive behavior were used for survival in nonbreeding season. Because birds used these character variations to communicate social signals, the dominant birds approached to the resources first, obtained more food and left the flocks for mating before the others.