It’s late September as I write this. As winter approaches, daylight gets shorter and shorter every day. If you want your coturnix quail to continue laying eggs reliably throughout the winter, you will have to provide them some supplemental lighting.
This isn’t complicated, though some think that it is. I simply string some white LED Christmas lights around the quail cages and set them on a timer so they come on a little before sunset. The timer is set so the quail get a total of 16 hours of light a day. That’s it.
For example: If sunrise it at 7:00AM and sunset is at 8:00PM, that’s 13 hours of daylight. So set your timer to give the birds an extra 3 hours of light: have it come on at 7:30PM (just before sunset) and go off at 11:00PM. Roughly adjust the timer over the weeks and months as sunrise/sunset changes. It doesn’t have to be exact or to the minute. “About” 16 hours a day will be fine.
I have read some folks that claim that a certain light spectrum is necessary to keep the quail healthy and producing quality eggs – I don’t think so. Not for the small homesteader anyway. My birds give me awesome quality eggs all year and I use cheap LED Christmas lights that I bought at Walmart. And my birds seem as happy as can be.