Duplicating the 1st bird should include it's animation. Then by clicking on the keyframes, including the 'time-zero' one, and then drag them to the time yo uwant them to be. Also, you can 'ALT-click-and-drag' the keyframes to duplicate them to where you need them WITHIN the same objects timeline. (The drag will only slide along that items line. You can't drag them to another objects timeline.) Hope this helps!