Order names linked to common name examples.
| 1 | a. Hind toe connected to anterior toes by a web b. Hind toe absent or else not connected to anterior toes by a web |
Pelecaniformes 2 |
| 2 | a. Nostrils located in raised tubes b. Nostrils not in raised tubes |
3 4 |
| 3 | a. Anterior toes webbed b. Anterior toes unwebbed |
Procellariiformes Caprimulgiformes |
| 4 | a. With 2 anterior toes and 1 or 2 posterior toes b. With 3 anterior toes and with 1 or no hind toe |
5 9 |
| 5 | a. Outer hind toe somewhat shorter than inner hind toe b. Outer hind toe decidedly longer than inner hind toe |
Trogoniformes 6 |
| 6 | a. Bill with a cere (swollen membrane covering the base of the upper bill) b. Bill without a cere |
7 8 |
| 7 | a. Tarsus (ankle above the toes) feathered b. Tarsus unfeathered |
Strigiformes Psittaciformes |
| 8 | a. Length of tail greater than length of wing b. Length of tail less than length of wing |
Cuculiformes Piciformes |
| 9 | a. Outer 2 anterior toes more or less grown together and provided with a common sole b. Outer 2 anterior toes more or less free or webbed, but without a common sole |
Coraciiformes 10 |
| 10 | a. Tarsus much compressed laterally, its greatest depth being 2 or more times its greatest width b. Tarsus not greatly flattened laterally, its greatest depth being less than twice its greatest width |
11 12 |
| 11 | a. Anterior toes connected by full webs b. Anterior toes lobed, each with a separate web |
Gaviiformes Podicipitiformes |
| 12 | a. Distance from bend of wing to tip of longest secondary much greater than distance from tip of longest secondary to tip of wing b. Distance from bend of wing to tip of longest secondary not greater than distance from tip of longest secondary to tip of wing |
13 Apodiformes |
| 13 | a. Hind toe inserted at same level as anterior toes; no horny frontal shield extending from bill to forehead b. Hind toe sometimes absent, if present usually inserted higher than anterior toes; or else with a frontal shield on forehead |
14 17 |
| 14 | a. Bill strongly hooked and provided with a cere; feet and claws usually strong and adapted for tearing flesh b. Bill neither strongly hooked nor provided with a cere; feet and claws not adapted for tearing flesh |
Falconiformes 15 |
| 15 | a. Bill, neck, legs, and toes very long; adapted for wading b. Bill usually shorter than head; neck, legs, and noes not elongated |
Ciconiiformes 16 |
| 16 | a. Bill constricted in middle; nostrils slitlike, overhung by a fleshy flap b. Bill not constricted medially; nostrils variable |
Columbiformes Passeriformes |
| 17 | a. Cutting edges of bill fringed or with serrations b. Cutting edges of bill smooth, without fringe or serrations |
Anseriformes 18 |
| 18 | a. Feathering of forehead extending into nasal fossae; nostrils either completely feathered or overhung by a horny flap; toes unwebbed b. Feathering of forehead usually not extending into nasal fossae; nostrils usually not overhung by a flap; toes sometimes webbed |
Galliformes 19 |
| 19 | a. Outermost primary usually as long as or longer than next primary, forming tip of wing; primaries often considerably longer than secondaries; front toes sometimes webbed b. Outermost promary considerably shorter than next primary; 2nd and 3rd primaries usually longest; primaries usually shorter than secondaries and concealed by them; anterior toes never fully webbed |
Charadriiformes Gruiformes |
Orders and common name examples: