A few weeks ago we discovered a decaying pigeon carcass hidden in a nook in the garden. When examined it was little but a collection of decaying feathers and bones; it had clearly been lying in it's last resting place for some months. We managed, without too much mess, to salvage the breastbone and the skull.
Having soaked them in mild detergent (shampoo) and allowed them to dry thoroughly I then bleached and disinfected them twice, overnight, with hydrogen peroxide (allowing them to dry in between). They have then been sitting drying thoroughly again in the bathroom for a week or more.
And here are the photographs. The structures are amazing. Some of the delicate structure of the brain case can be discerned as can the delicate fine structure of the sternum. The sternum especially is wonderful to handle: it weighs absolutely nothing and feels like the most delicate waxed paper, which isn't so obvious with the skull.
The skull is 56mm from back to the tip of the bill, 20mm high, 20mm wide.
The sternum is 72mm long, 48mm high, 50mm wide.