The character of the bill and feet of a bird often may serve as a guide to its habits and an indication of its relationship to other birds. For example, seed-eating species have short stout bills that are used in cracking seeds, woodpeckers have long chisel-like bills for drilling into wood, and owls have hooked beaks for tearing apart animals they capture with their long curved talons. Often all the members of a bird family have similar beak and foot structure but this is not invariably true because the members of a family may have become adapted to different modes of life.

The illustrations (pages 65-69, figures 1-45) depict variation in beak and foot structure. The families shown with the species representing them are as follows:

Grebes: Order Podicipediformes
1. Grebes: Family Podicipedidae—Western Grebe

Pelican-like birds: Order Pelecaniformes
2. Pelicans: Family Pelecanidae—White pelican (Foot as in figure 3)
3. Cormorants: Family Phalacrocoracidae—Double-crested cormorant

Stork-like birds: Order Ciconiiformes
4. Herons and Bitterns: Family Ardeidae— Green heron (note comb on middle toenail)

Goose-like birds: Order Anseriformes
5. Ducks, Geese, and Swans: Family Anatidae—Bufflehead

Hawk-like birds: Order Falconiformes
6. American Vultures: Family Cathartidae—Turkey vulture
7. Kites, Hawks, and Eagles: Family Accipitridae—Red-tailed hawk

Fowl-like birds: Order Galliformes
8. Quail and Pheasants: Family Phasianidae—Gambel’S quail

Crane-like birds: Order Gruiformes
9. Rails: Family Rallidae—American coot

Plover-like birds: Order Charadriiformes
10. Plovers: Family Charadriidae—Killdeer
11. Snipe, Sandpipers, etc.: Family Scolopacidae—Least sandpiper
12. Avocets and Stilts: Family Recurvirostiudae—American avocet
13. Phalaropes: Family Phalaropodidae—Northern phalarope
14. Gulls and Terns: Family Laridae—Ring-billed gull (immature)

Pigeon-like birds: Order Columbiformes
15. Pigeons and Doves: Family Columbidae—Mourning dove

Cuckoo-like birds: Order Cuculiformes
16. Cuckoos, Roadrunners, etc.: Family Cuculidae—Roadrunner

Owls: Order Strigiformes
17. Barn Owls: Family Tytonidae—Barn owl (Note comb on front toenail)
18. Typical Owls: Family Strigidae—Screech owl (Foot similar to Tytonidae but no comb on nail)

Goatsucker-like birds: Order Caprimulgiformes
19. Goatsuckers: Family Caprimulgidae—Common nighthawk (Note comb on middle toenail)

Swifts and Hummingbirds: Order Apodiformes
20. Swifts: Family Apodidae—Vaux’s swift (Note bare spine-like shafts of tips of tail feathers)
21. Hummingbirds: Family Trochilidae—Allen’s Hummingbird (female)

Roller-like birds: Order Coraciiformes
22. Kingfishers: Family Alcedinidae—Belted kingfisher

Woodpecker-like birds: Order Piciformes
23. Woodpeckers: Family Picidae—Yellow-bellied sapsucker (Note the zygodactyl foot—two toes in front, two behind)

Perching birds: Order Passeriformes
*24. Tyrant Flycatchers: Family Tyrannidae—Say’S phoebe
25. Larks: Family Alaudidae—Horned lark
26. Swallows: Family Hirundinidae—Violet-green swallow
27. Jays, Magpies, and Crows: Family Corvidae—Scrub jay