cold, and fertile eggs

[curliet]

We have coturnix quail in pens in our garage. We're in Mi, the midwest part of the state. It's been pretty cold here and we've started keeping a heat bulb on to keep the water from freezing. The bulb doesn't make it warm in the garage, but does keep it just above the freezing point. Is there a limit as to how much cold the eggs can be exposed to before they lose fertility?
We're starting to look forward to hatching and about getting the incubator back out pretty soon, and are wondering just how long the eggs can be left in the pen in these temps before losing their fertility or not being useful for hatching. I've been trying to get out there to check every few hours and bring eggs into the house, but haven't been able to get a handle on when they are laying. I think that the cold is screwing up any kind of normal laying schedule.

At first I was just leaving the light where it could shine into both pens, for the warmth, but then realised that the light all night long would get them too agitated and now I cover them with a light cloth at night to darken the pen, remove it in the morning. But they still seem to be laying at all times of the day and night.

Can someone give me an idea of what kind of wndow of time and temps I can look for?

 

[quailbrain]

We've been at 28 and just hatched a clutch of coturnix. I think if the eggs don't freeze completely they can stay fertile but if freezing has damaged the egg components a fertile chick can develop to a point but die a week or so into the development.