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.
1 Wavelength shift: = new-rest. rest is the wavelength measured if the object is at rest and new is the wavelength measured for the moving object. 2  Doppler effect: = rest Ã Vradial/c, where Vradial is the object's speed along the line of sight and c is the speed of light.3  If new rest, the object is moving away (redshift).he doppler effect will not affect the overall color of an object unless it is moving at a significant fraction of the speed of light (VERY fast!). For an object moving toward us, the red colors will be shifted to the orange and the near-infrared will be shifted to the red, etc.