Possible Brood Patch
Wikipedia def of brood patch: "A brood patch is a patch of featherless skin that is visible on the underside of birds during the nesting season. This patch of skin is well supplied with blood vessels at the surface making it possible for the birds to transfer heat to their eggs when incubating." This Cooper in my yard looks like she may have a brood patch showing.
Adult Cooper's Hawk (Accipiter cooperii)
Accipiter cooperiiCooper's hawkadult cooper's hawkhunterpredatorraptorgarland texasbrood patch