Ah! I thought it was the distance from the base of the pole to the bird.
Okay. The height of the bird:
With the tangent: height/length = tan(angle)
tan(25) = height/100---> height= 100*tan(25)= 46.63 ft (make sure the calculator is in degree)
But this is the height from the nest, from the ground is +30:
76.63