Japanese Quail may start laying eggs as soon as 42 days, some even earlier. They are similar to chickens in that they are stimulated to lay by the light cycle.
They can readily lay under artificial light. We have ours on a 16/8 hour cycle. We have reasoned that leaving the lights on longer could produce bigger eggs but we strive for some uniformity in our eggs. We let the hens rest and the dark helps keep the cockbirds a little quieter.
As stated, we strive for eggs that average over 14+ grams. We allow hens that make the weekly weigh-ins as keepers to “practice” laying up to ~16 weeks. At 16 weeks the hens that made the “weight cuts” must now make the tryouts for the “egg cuts”.
The egg laying trials are easy enough. We leave all birds and eggs in their individual pen for 5 days. At the end of 5 days, we reach in and collect all the eggs.
#1 There should be 5 eggs, 1 egg per day. #2 We weigh the eggs #3 We visually inspect the eggs for proper shape and coloring. #4 It is important that the Quail hens keep their weight up too, its demanding work on a 12-14+ oz. bird to deliver an egg weighing over a half-ounce everyday.
After this grading process 1 or 2 of your original 10-12 hens may make it to the breeder pen. This may be a good reason to gather your original hatching eggs from several different sources.
With the standard being 9 grams for a normal Coturnix egg, the egg below is a very large egg for a Japanese Quail hen. It is atypical and may be a double-yolked egg. Just like chickens, Quail can lay eggs with 2 yolks. It happens occasionally when a bird skips a day laying an egg and then 2 ovum are encased in 1 eggshell the next day. These eggs should not be set, as they are not uniform and will probably not hatch. Hens that lay eggs with 2 yolks, consistently, should probably be culled from your breeding stock.