Preparing the Next Generation of Choughs

It takes 19-21 days for a lay to hatch, so the incubated eggs are under constant supervision. They are regularly weighed, so the humidity and temperature of the incubator can be adjusted appropriately. An egg losing too much weight indicates that humidity is too low, while an egg not losing weight at all means the humidity is too high. They are also rotated, to stop the shell membrane sticking to the embryo. This is done mainly by the machine, but also requires some delicate manual turning.

And once a day the eggs are “candled”. A light is shone on the shell in a dark room to look for signs of development including the air space within the egg into which the chick will push through before it eventually hatches, and which should have a uniform line.

This process of breaking into the air cell is called “internal pipping”. “External pipping”, as you might expect, is the actual breaking through the shell.

We stop turning the eggs when the chicks begin pipping internally. We then boost the humidity to prevent the membrane drying out allowing the chick to hatch out safely Eggs will pip internally at different times within a clutch, so it’s essential to have another incubator set at a higher humidity to move hatching eggs across into – equipment gratefully purchased with support from Natural England.

Hatched chicks go into a “brooder”, an artificial nest environment which provides biosecurity -it can be kept clean and regulates humidity and temperature. This is essential, as newly hatched chicks can’t regulate their own temperature. While in the brooder, they hear recordings of choughs, including the call the parents make when they enter the nest with food, which prompts them to beg.

Around seven to 10 days after hatching, they begin to open their eyes and need to see black and red, not human hands. So all staff wear black gloves and use red tweezers, which feel like a bird’s bill, when feeding them.