Call Learning in the Carduelinae: Ethological and Systematic Considerations

Mundinger, P. C. (Department of Biology, Queens College of C.U.N.Y., Flushing, New York 11367) 1979. Call Learning in the Carduelinae: Ethological and systematic considerations. Syst. Zool. 28:270-283.-Experiments and field observations document vocal imitation in six cardueline species representing four genera. Flight call learning was found in all birds studied; learning of many other call types was observed in two genera. Additional evidence extends call learning to other carduelines bringing to eight the total number of genera in which call learning has been observed. Call learning is perhaps characteristic of subfamily Carduelinae, and the taxonomist should consider the possibility that learning may affect the patterns of all adult cardueline vocalizations. The taxonomic value of cardueline calls in particular and passerine calls in general is re-examined in light of this extensive call learning. It is suggested that the ontogenetic, learned modification in call pattern can be eliminated from the taxonomic analysis, and that calls may then be taxonomically valuable behavioral characters. The problem of homologizing behavior is discussed, with criteria for homology applied to two call types, both associated with call learning. Cardueline flight calls are autapomorphic characters useful as species specific characters, while social/alarm calls are synapomorphic at the subfamilial level and can be used as taxonomic characters at the family level. [Vocal imitation; bird calls; homology; behavioral characters; Carduelinae; nine-primaried oscines.] Bird vocalizations are frequently used as taxonomic characters (reviewed in Lanyon, 1969; L6hrl, 1963). We know that many passerines learn their song patterns (Marler and Mundinger, 1971), but this is not a great concern for systematists who often work with environmentally modified characters (Lanyon, 1969). Besides, bird songs have features valued by systematists: there are species-typical constraints on song learning; the patterns of many species are stable from year to year; and song generally functions as a reproductive isolating mechanism. At first thought, bird calls might appear even better taxonomic characters as they are usually considered genetically fixed or innate, i.e., they develop normally in the absence of external models (Lanyon, 1960; Hinde, 1970; Thielcke, 1976:99). But scattered cases of call learning are now known (Lanyon, 1957; Thielcke, 1960; Gwinner and Kneutgen, 1962; L6hrl, 1963; Mundinger, 1970; Marler and Mundinger, 1975). In groups where call learning may be common some systematists tend not to use adult learned calls as characters and instead rely on juvenile calls, in which learning seems not to occur (L6hrl, 1963). As a class, behavioral characters are rarely used in taxa above the family level (Atz, 1970). And in particular, vocal characters, represented by specifically distinctive song and call patterns, are used at the species level. However, Marler (1957) has suggested that some calls, such as the flight call, social/alarm call, and aggressive call, function in both intraand interspecific communication and thus appear to be selected for only moderate degrees of specific distinctiveness. Such calls may therefore be useful in classifying higher taxonomic categories. Marler used cardueline finch calls to illustrate vocalizations selected for moderate degrees of specific distinctiveness. Several years ago I found that some members of the genus Carduelis alter the fine-structure of their flight calls by imitating conspecifics, and they can even imitate alien species call patterns (Mundinger, 1970). This has systematic implications, for characters thought to