Left foot of Panyptila melanoleuca.
Cypselinæ. Tarsi feathered; phalanges of the middle and outer toes three each (instead of four and five). Hind toe directed either forward or to one side, not backward.
Tarsi feathered; toes bare; hind toe directed forward … Cypselus.
Both tarsi and toes feathered; hind toe lateral … Panyptila.
Chæturinæ. Tarsi bare; phalanges of toes normal (four in middle toe, five in outer). Hind toe directed backwards, though sometimes versatile.
Tarsi longer than middle toe.
Tail-feathers spinous.
Shafts of tail-feathers projecting beyond the plumage … Chætura.
Shafts not projecting, (Nephæcetes) … Cypseloides.
Tail-feathers not spinous … Collocallia.