Birds have feathers for insulation — to keep body heat in, and the cold and rain out. They preen the feathers with a special oil from the preening gland just above their tailfeathers. But the same feathers that hold a mother bird's heat in could keep her body's heat away from her eggs and her babies! What can she do to share her body warmth when she's incubating eggs? That is possible with a special adaption: the broodpatch.
The female peregrine, as well as the male develop a brood patch during the breeding season. Changes in hormone levels like prolactine, progesteron and estradiol during the nesting season start the process. These hormones start ro rise as soon as the second last egg has been layed. Down feathers on the bird's tummy, and even some contour feathers, suddenly get very loose. In the peregrine falcon those feathers just fall out. When the feathers fall out, tissue changes start to happen too. The tissue in the tummy area swells. The tissues hold more water, and more bloodvessels are starting to grow in that area. These changes make the bird's tummy skin almost as hot as the body's interior.
When the incubating peregrine sits on the eggs, the skin muscles open up the brood patch. Then the parent sits down and wiggles its body back and forth a bit. The sensitive skin feels for the eggs so the parent can settle where the skin makes best contact with the eggs. The parent keeps turning the eggs almost every hour. This is done to prevent the fast growing enebryo to stick to the shell and to take care the eggs are evenly warmed by the broodpatch!
For the parent peregrine the area of the broodpatch is a problem in their own thermoregulationsystem of the body. In order to keep it's own temperature on 104F they have to eat a lot, so there is a constant suply of energy.
This tiercel Kaver of Rochester is the resident male of the Kodak Tower eversince 2002 when he replaced Sirocco who did not return after the winter. His partner is the beautiful and exceptional Mariah who is the resident female for 10 years now. Mariah has raised and fledged 38 juvi's !!
Orville in the nestbox sraping a bowl for the eggs. And sitting on the ledge. Both peregrines spent a lot of time near the nestbox. Wonder when Scout will start laying. 
Aisha and Vento: estimated date of hatching: 8th of april, so still more than 2 weeks to go.
Simply beautiful, the two of them.
Courtship and copulations keep going on. He keeps offering her prey and they do talk a lot!!Tomorrow a second egg?
This is a great site to learn more about the DDT disaster in the 50-60ties. And read about all the efforts that have been made to reintroduce the Peregrine Falcon in Virginia. And how the Center for Conservation Biology in collaboration with the Virginia Department of Game & Inland Fisheries conducts annual monitoring of the Virginia peregrine falcon population. 
This picture gives a very schematic impression of what is happening inside the egg in 33 days.
Winter, cold, snow and temperatures below zero, this tough lady does not care. 
Dawn in Cleveland. No extra snow but the temperature is far below zero: -7 C. I'm not happy with that at all. SW and Buckeye must be having a very hard time, keeping the eggs alive. And staying warm enough themselves. The broodpatch is a large area without down protection, they are loosing a lot of bodywarmth that way. The broodpatch is very vasculair, and vasodilitation is optimal in order to transfer as much warmth possible to the eggs. In these weather conditions it takes loads of energy from SW and Buckeye to keep their own thermoregulation up and running. So Buckeye catch many flickers from the square below so you and SW can eat and keep the eggs on 38 C. We send you warmth and energy and we keep our talons crossed!
