Pour the 2 packages of unflavoured gelatin on top of the water.
Add 1/2 cup boiling water to the gelatin mixture and stir until the gelatin is completely dissolved.
Add the corn syrup and stir until combined.
Add the birdseed and mix well.
Place the bowl in the refrigerator for about 10 minutes until the liquid firms up enough that it won't leak out from under the cookie cutters.
Set your cookie cutters onto a parchment lined baking sheet and fill them with spoonfuls of the birdseed mixture. Using the back of the spoon, press down the birdseed mixture firmly to fill in all the gaps. Fill the cookie cutters to the top.
Press the drinking straws into each of the shapes leaving at least 1/2" of space between the hole and the edge of the shape.
Place the ornaments in the refrigerator overnight.
To remove the cookie cutters, gently pull the metal away from the edges on all side then gently push the birdseed ornaments out of the cookie cutters. Gently pull the straws out.
Thread a piece of twine through the hole and tie the ends in a knot.
Hang the birdseed ornaments from tree branches, leaving room nearby for the birds to perch on while eating.
When you place the mixture in the refrigerator, right after you've added the gelatin to the birdseed, make sure you don't keep it in the fridge for too long. If any of the gelatin "breaks" when you stir it, you need to microwave the whole bowl to melt it and try again. The birdseed/gelatin mixture needs to be thickened slightly in the fridge until it has the consistency of a thick syrup. If the gelatin is set more than that before you spoon it into the cookie cutters, the ornaments will end up being crumbly. Just make sure it's set enough so that it doesn't all leak out from under the cookie cutters.