I had the luxury of two hummingbird nests within sight in my backyard. I watched the eggs of an Anna's hummingbird for some time. I knew that it was possible they would be hatching soon. I checked them one morning and mom was "out" but the eggs were still there. 1.5 hours later, I checked again and they were hatched...so, I knew these guys were no more than 1.5 hours old and still "hatching" from their eggs. It was amazing. The two together were smaller than an M&M candy.