The shape and size of a bird's bill is highly specific to its diet and lifestyle. For example:
* Birds of prey have hooked bills for tearing flesh.
* Hummingbirds have long, thin bills for reaching into flowers.
* Woodpeckers have strong, chisel-like bills for drilling into wood.
* Ducks have flat, wide bills for filtering food from water.
So, while birds don't carry paper bills, they have very specialized bills that are essential for their survival.