The incubator itself is nothing more fancy than a big polystyrene container. There are channels in the bottom to hold water; while the top has a small heater, with thermostat attached, and a small perspex square to look through. There's also a wire tray that sits on top of the water channels. Add a thermometer on a little stand; and that's pretty much it. You select clean eggs with smooth skins, and store them for no more than a few days after being laid before stabilising the temperature at 103, filling one of the channels with water, and laying the eggs on the wire tray. You mark one side with a pencil cross; the other with a zero. For 18 days (for chicken eggs) you turn the eggs morning and night; clockwise, then anti-clockwise. If you keep turning them in the same direction they get all twisted up inside and don't develop. Of course the hen does all this keeping them warm, and humid and turned properly all by herself.
After 18 days you make sure there is water in the outside channel (more in dry climates), turn them for the last time and close the lid. Under no circumstances must you open it until the chicks have hatched.
Before I left for work this morning I could hear a faint chirruping. And now there are about four or five that have come out of their shells, and I can hear them scrabbling around amongst the broken shells, chirping madly. Joel and I watched two come out at the same time, about half an hour ago. The first thing you see is a small triangular piece of shell broken off. Then the baby chick's single tooth breaks through the membrane. There's usually a pause of about an hour while it recovers from this exertion. Then it starts to break the egg in a zig zag pattern, around the broadest part of the egg. This might take half an hour. Then all of a sudden, the egg breaks neatly in two, and panting and puffing, the chick unfurls itself and kicks free of the egg. It's wet, of course, and can hardly hold up its head. Peering into the box, you are very relieved to see it panting and breathing. But within half an hour, it's sitting up; and within another half hour, it's dry and fluffy.
Sitting at my desk, I can hear them moving around so vigorously I think they're going to lift the lid and come out, though I know that's impossible. As I go and peer into the box again, I can see the humidity starting to fog up the little window; one or two more eggs have their first little triangle broken, and are wobbling back and forth; while some are not moving at all. I'll give them another 24 hours, then will have to open the box and start to feed the little ones, knowing that those who've not yet made it out, probably won't, or are unfertilised or damaged in some way.
Watching the two little ones emerge — one pale, one dark — with my own child was pretty extraordinary. He's seen this before, but doesn't remember; and at 15 is suitably intrigued, sentimental and concerned about them.
Warm thoughts tonight, then, of the many friends and facebook friends who've given birth recently: Nicole, Amy, Belinda, Clare, and yesterday, Genevieve; and very soon, Kim; and next year, Melanie. And for all those who nurture, in all ways. Well, it was work-in-progress day for our graduate students today; and I know we all felt so proud of them.
So if you're up at Ceres around about Christmas or the New Year, and see some smaller, younger hens up there, you'll know you were a bloggy witness to their birth.
And just because we can link, here's Joni, in Japan: