pie bird [pahy burd] noun
Also called pie vent, pie chimney, pie whistle or pie funnel. A tall, narrow, hollow gadget, usually ceramic, placed in the center of a two-crusted pie to allow and encourage steam to vent, which discourages the filling from boiling over and helps the pastry crust stay crisp. A pie bird is often shaped like a bird with an open beak, hence the name, but can come in other shapes as well.
An additional benefit is that they can help the center crust remain domed and keep it from falling if the raw dough is formed snuggly around the ceramic tool, which helps it stay put. Although ceramic is the classic material for pie birds, they can also be found made from silicone. They have become quite collectable and new as well; antiques are easy to find. There is even a Pie Bird Collectors Convention.
There are several ways one could use a this tool, but the most accepted technique is to line the bottom of your pie plate with the bottom crust, place the pie bird in the center and pour/scrape your filling into the crust and around the pie bird. Roll out your top crust and cut a small slit in the center. Carefully unroll/place the top crust on top of the filling, easing the pie bird up through the slit; it should be snug. Crimp edges as desired and bake with the tool in place. Allow the pie to cool. Cut first wedge and serve, then remove pie bird and continue to slice and serve your pie.