Originally Posted by **studiot** The original question is rather vague so it is diffcult to know what is required without further discussion from the OP. |

On the contrary. The OP was very clear

Question a: If a bird is flying straight and level at a steady speed, what energy changes are taking place?

Answer b. Since the speed is steady then the kinetic energy is constant. Since the flight is level then the gravitational potential energy is also constant. Therefore the total energy, being the sum of the two, is also constant.

Question b. And what energy changes are taking place when a bird dives down to catch a fish from a lake?

Answer b. When a bird dives down its speed increases and so its kinetic energy increases. Since its moving down its potential energy decreases. Those are the only changes that we know happen. If we knew how the speed of the bird changes with height then would could determine if the total energy is constant. But since all we know is that the bird dives down we have no knowledge about its speed. We can only assume that it increases as its height decreases.

So your claim that the question is "rather vague" is clearly wrong, i.e. its quite clear.