(5-4) Diffraction requires that the slit has a width that is of the same order of magnitude as the wavelength. So if Cormorant reckons he could get through a 20 cm slit with his wings tucked in, see if you can calculate the speed he would need to travel at, to achieve a 20 cm wavelength.
To put this velocity in perspective, once you’ve calculated it, work out how far Cormorant would travel at this speed in the lifetime of the universe (around 4.3 x 1017 seconds).