Vocalizations of Common Ravens in Virginia

Abstract

--I tape recorded 1,210 vocalizations and observed the behavior of Common Ravens (Corvus corax) in southwestern Virginia from 1972 through 1976. Eighteen call types were identified and observed in conjunction with behavior at a communal roost, a landfill, and nest sites. I speculate that different call types were associated with excitement, agonistic interactions, aggression, alert, courtship, submission, and thwarting. Common Ravens in Virginia and handreared, captive ravens in Germany shared six call types, suggesting that the use of these call types may be innate. Although Common Ravens in Virginia, Alaska, and Germany gave many similar call types, locally learned call types may be present in each geographic area. Numbers of shared call types suggest that vocal behavior of ravens in Virginia resembles that of other North American ravens more than European ravens. The diversity and complexity of Common Raven (Corvus corax) vocal behavior have interested ornithologists and ethologists for years. Although ravens may be locally numerous at food sources, such as dumps (Mylne 1961, Dorn 1972, Brown 1974, Conner et al. 1975), and at communal nocturnal roosts (Cushing 1941, Coombes 1948, Lucid and Conner 1974), their populations are typically of low density, especially during the nesting season (Hooper et al. 1975). Their sparsity in number, coupled with their high intelligence (Bent 1946, Knight and Call 1980, Bruemmer 1984), extreme wariness, and frequently inaccessible nest sites, make it difficult to record their vocalizations within social context. Gwinner (1964) attempted to overcome these obstacles by studying hand-reared, captive ravens, but normal behavior and related vocalizations could have been altered by captivity. Studies in North America by Dorn (1972) and Brown (1974) included some aspects of Common Raven vocal behavior. Dorn recorded and made audiospectrograms of several different vocalizations, but he was unable to detect distinct behavioral associations with them. Brown (1974) recorded and made audiospectrograms on about 25 different vocalizations and described, in detail and when possible, display postures associated with many of the calls and their behavioral context. The Common Raven population in the central Appalachians is disjunct from the rest of the population in Canada and the United States (AOU 1983). Thus, vocal behavior of Common Ravens in Virginia may differ from other North American populations as well as from those in Europe. I sought to document the vocalizations and their social context in these birds, and compare my observations with those of comparable studies in North America and Europe. I was particularly interested to see how Gwinner's (1964) findings on hand-reared, captive ravens applied to wild ravens. Such comparisons may provide insight on determining which aspects of raven vocal behavior are innate and which are learned.