This plain-looking black bird, common in open savanna and pastureland of Central and northern South America, has one of the most intriguing breeding systems of any bird. Individuals live in social groups of 1–5 pairs that defend a group territory. All females of a breeding group lay their eggs in a single nest, and the joint clutch is incubated and cared for by all members of the group. Joint nesting also occurs in other members of the Crotophaginae—the Smooth-billed Ani (Crotophaga ani), the Greater Ani (C. major), and the Guira Cuckoo (Guira guira). The unusual nesting habits of the Groove-billed Ani include the females' behavior of removing eggs from the nest before beginning to lay their own.
This ani feeds on orthopterans, other insects, spiders, and small vertebrates, which individuals capture as they walk or hop through vegetation. In open pasture-lands of Central America, anis are typically seen with livestock, chasing prey that move or fly up as the animals walk through the grass.
The most detailed description of the natural history of the Groove-billed Ani was by Skutch ( Skutch 1959b )—an account based on observations in Costa Rica, Honduras, and Guatemala. His description of characteristics and behaviors is insightful and entertaining, and some of the natural history reported in this Birds of North America account is based on his work. The communal nesting habits of this bird were the focus of studies in Costa Rica during the 1970s and 1980s by Vehrencamp, Koford, and Bowen (Vehrencamp Vehrencamp 1977 , Vehrencamp 1978 , Vehrencamp 1982b ; Koford et al. Koford et al. 1986 , Koford et al. 1990 ; Vehrencamp et al. Vehrencamp et al. 1986 , Vehrencamp et al. 1988 ; Bowen et al. Bowen et al. 1989 , Bowen et al. 1991 ). They quantified habitat variables, reproduction, dispersal, and survival in a color-marked population. The species has been the focus of several small-scale studies of foraging behavior in El Salvador, Costa Rica, and Texas ( Rand 1953 , Smith 1971e , Bolen 1974 ). A recent paper on the species in the U.S. focused on vagrant records and characteristics that could be used for distinguishing Groove-billed and Smooth-billed anis in the field ( Mlodinow and Karlson 1999 ).