Q: How long before pigeons lay eggs after mating?
It usually take 2 weeks before the mated hen pigeon start laying its first egg. The 2nd egg might come in after 2 days and it may take about 18 days for the eggs to hatch. After the squabs comes out from the eggs it might take 15 to 25 days for the pair to lay the 2nd batch of eggs.
Here’s a link to view pictures of a baby pigeons from hatching on day 1 to after 30 days.
http://www.speedpigeon.com/baby_racing_pigeon.htm
Q: How long does a pigeon sit on her egg?
The female pigeon usually sits on her eggs starting late in the afternoon all the way through the night and switches with the male pigeon in around 10am the next morning so the male actually takes the day shift. On some pair if the hen wanted to stretch, eat or drink and needs to stand up the cock takes over the nest until the hen is ready and comes back to the nest.