I think the pie funnels are called pie birds because of the rhyme and not v.v.
Does anyone still use them?
I thought they were for holding up the middle of the crust if the filling shrank on cooking, to give the pie a rounded top.
In our family we used inverted an eggcup. As well as the standard white pottery funnels they used to sell colourful ones that looked like blackbirds with yellow beaks.