1. Bill from forehead, .74; wing, 3.90; tail, 2.40. Lower
mandible much weaker than the upper. _Hab._ Europe …
var. _curvirostra_.[110]
2. Bill from forehead, .80 or more; wing, 4.00; tail, 2.50.
Lower mandible as strong as the upper. Hab. Rocky Mountains of
United States, and mountainous regions of Mexico … var. _mexicana_.
3. Bill from forehead, .60 or less; wing, 3.30; tail, 2.20.
_Hab._ North America generally … var. _americana_.