PBS
Pbs Learning Media: Bird Food and Bird Beaks
There are almost as many types of bird beaks as there are types of food that birds like to eat. This collection of images shows a wide range of beaks and the types of foods handled by each.
Merriam-Webster
Merriam Webster: Dictionary Illustration: Bird Beaks and Bills
Labeled illustrations demonstrating the diversity of bird mouth parts, each adapted for particular purposes.