Why do birds need full spectrum lights to fill the light?

Not the sun. The light source of full-spectrum lamp has full-spectrum characteristics and can replace the light generated by solar spectrum. The principle of this kind of lamp is similar to sunlight, which can provide all the light needed for the healthy growth of birds. A full-spectrum metal halide lamp can emit light closest to natural light, because the light it emits is full-spectrum, that is, all light waves have it.