Scan sampling and focal sampling methods were used to determine the behavior development of the nestlings of Great Bustard (Otis tarda).The results indicated the proportion of resting and standing behavior is increase during their first 3 days,while the proportion of crouching and singing was decrease.The proportion of each behavior will be more similar with the juveniles as their growing,however,they do not show a rhythm obviously.The nestlings spend 51.7% of time resting,16.1% standing,18.8% walking,3.2% preening,and 6.1% winging.The nestlings take a higher percentage of their time to rest in the whole duration of growing,increase foraging and preening and reduce singing and crouching as their growing.