This year the red-tails laid their eggs on March 11, 14, 18 and 21. This is later than the previous few years. In 2009 they laid their eggs on March 6, 8 and 12 and in 2010 they laid their eggs on March 3, 6, and 9.
The eggs are incubated for between 28-35 days so the eggs are unlikely to begin hatching until the second or third week of April. Incubation was only intermittent until the third egg was laid so it is likely that at least the first three eggs will hatch about the same time. Cold weather can slow the incubation process down and it can take even longer.
Watch for the female periodically turning the eggs. She will do this every couple of hours. This ensures that the eggs warm evenly and keeps the embryo membrane from sticking to the shell.
The eggs are typically maintained at between 98 and 100 degrees. You may notice an area on the mother's belly where the feathers look more sparse---many birds develop a "brood patch" which is an area where the bird looses some of its feathers toward the end of the egg laying period. This area also develops additional blood vessels to bring warm blood closer to the skins surface. This is the area of her body that she keeps in close contact with the eggs when she is lying on them.
It is also okay for the parents to be off the eggs for limited periods. Eggs can survive a substantial amount of cooling. Cooling tends to slow down development but not cause harm unless it is prolonged.Eggs are much more vulnerable to heating--just a few degrees above normal can be lethal to the eggs.
Live Video: Raptor Cam
Caught on cam: Both hawks in nest, 3/28
Photos: 4 eggs in the nest
Photo: Raptor Cam Adult flying next to the US Bank Tower by Bob Sallinger