1 Many people find that boxes with a 1.25 or 1 1/8 hole restrictor on them before an egg is laid are not utilized, even by smaller birds like titmice and chickadees. 2  If the entrance hole is enlarged (e.g., by woodpeckers or chewing rodents), put a hole reducer on it.
The Doppler effect widens the spectral lines of rotating objects because the wavelengths changes from blue or red. Blue-shifted, red-shifted, and non-shifted photons mix together to get how its rotating.
We hear it as the change in pitch of a train's horn as it passes us, says Watson. In light waves, it causes things moving towards you to shift to shorter wavelengths at the blue end of the spectrum. And objects moving away from you shift to longer frequencies, at the red end of the spectrum.. Astronomers used the Doppler effect to find the new solar system, says Watson.