Two eggs were laid before we realized what was happening. The hen laid the third egg on May 13, and the fourth and final egg the next day.
The parent killdeer start sitting on the eggs to incubate them as soon as all the eggs have been laid. The killdeer embryos inside the first-laid three eggs do not start developing while the eggs are sitting out in the cold. But when they feel the warmth of the parent killdeer, all four killdeer embryos start developing at the same time.
When someone comes too close to the nest, the killdeer goes into its "broken wing" act, drawing attention to it and away from the eggs or the chicks.
The normal gestation period is 24 to 28 days, so we're expecting to see the chicks around June 7-10. We're hoping all four chicks survive, but we must let nature take its course. We will keep the cats away, though.
You can learn more about killdeer at these sites: Environment Canada and Birdwatching.comDigital photography: Many thanks to Jack F. Grover and his marvelous Sony Mavica; both courtesy of Visual Sound.
Also see Jack's photos of his pride-and-joy collies at Keystone Collie Club.