Firstly, you could try to draw a "half-parabola" where the

value is the time in seconds and the

value is the height of the bird. So it would look a bit like the right part of the graph of

. Then you try to make an equation that fits the particular curve you get. You can use the y-intercept point (the value of

when

, that is the initial height), the x-intercept point (the value of

when

) and other features of the parabola to model an equation fitting a bird falling from the sky. You must always consider the

unit (time in seconds) and the

unit (height in ... meters ?).