Taxonomy

Cuckoos belong to the family Cuculidae, which is a group distributed worldwide, typically of dull plumage, usually grayish brown or partly rufous. The Cuculidae are long-tailed (8 to 10 tail feathers), with exposed nostrils, and bristles at the corners of the bill, with zygodactylous feet. Bill varies in size and shape, but is always compressed and more or less decurved at the tip. Several species of Cuculidae are found in north America, including the Groove- billed Ani, Smooth-billed Ani, Greater Road Runner, Yellow-billed Cuckoo, and Black-billed Cuckoo (Terres, J. K. 1980).


Groove-billed Ani Crotophaga sulcirostris	Smooth-billed Ani Crotophaga ani

Yellow-billed Cuckoo Coccyzus americanus	Black-billed Cuckoo Coccyzus erythropthalmus

Greater Road Runner Geococcyx californianus

Two species of Yellow-billed Cuckoos were described by Ridgeway (1887). He distinguished the western sub-species of Yellow-billed Cuckoo (Coccyzus americanus occidentalis) from the eastern sub-species of Yellow-billed Cuckoo (Coccyzus americanus americanus) by being slightly larger and grayer in coloration. The western subspecies (C. a. occidentalis) once ranged from the Rio Grande River to California and north to British Columbia in mesquite and cottonwood-willow habitat, while the eastern subspecies (C. a. americanus) was found in the deciduous forest east of the Rocky Mountains. This distinction has been recognized for most the the past century, although several authors have questioned the separation ( Laymon, pers.com. in Halterman 1991), but little data had been presented until Banks (1988). He concluded that populations of the Yellow-billed Cuckoo west of the Rocky mountains have average wing lengths slightly greater than those of eastern America, but the difference was not sufficient for taxonomic recognition and the species is best considered monotypic. Morphological differences were described by Franzreb and Laymon (1993) and they found morphological differences between the two species. Because of the current lack of agreement concerning sub-specific taxonomy, survey data collected in this study do not differentiate between the two sub-species of Yellow-billed Cuckoo.