Actually it doesn't fall into the nest
Vertical component of the velocity, v of mouse after travelling vertical distance of 12 m is given by
v^2 - (4sin 35)^2 = 29.8112 or v = 15.51 m/s
time taken to travel 12 m downwards = (15.51 - 4sin 35)/9.81 = 1.35 s
Horizontal distance traveled in this time = 4(cos 35)1.35 = 4.41 m
But the eastern end of the nest is only 4.15 m away