Describes the physical characteristics, usages, and probable functions of 11 vocalizations of adult Black-capped Chickadees and 2 of the young. Some modifications of the vocal repertoire as compared with other passefines are associated with sociality and hole-nesting. The Fee-bee, usually considered the song of this chickadee, is less complex than some call notes and also has some differences in function compared to the songs of other passefines. The two most complex calls (Chick-a-dee and

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... e) are associated with social activities. Vocal signals tend toward sexual segregation, which may be important in a monomorphic species. The vocalizations of this species are compared with those of other parids, and selection pressures acting on the structure of vocalizations are discussed. The more complex vocalizations of this species are being studied extensively as mentioned in the accounts below, and are only generally described in this paper. THE Black-capped Chickadee (Parus atricapillus) is a particularly interesting species for the study of vocal communication for at least two reasons. It lives in small flocks during the winter and hence may have more elaborate or different vocal repertoires than less social species. Furthermore it nests in holes, a habit sometimes associated with modifications of display repertoires (von Haartman 1958). Black-capped Chickadee vocalizations have been examined by several workers. Odum (1941) provided a phonetically based classification of the vocalizations as part of a larger study of their behavior and ecology. Song was discussed by Dixon and Stefanski (1970) and precopulatory vocalizations by Dixon et al. (1970). The closely related Carolina Chickadee (P. carolinensis) was the subject of a message-meaning analysis by Smith (1972). METHODS We conducted this study at the University of Wisconsin--Milwaukee Field Station, Saukville (Ozaukee Co.), Wisconsin, from September 1970 to December 1974. This population of chickadees was color banded for individual recognition by Charles Weise, who made available data on age, sex, and winter and breeding locations for most individuals. It was not always possible to identify color bands when birds were in dense vegetation, so some unidentified birds were used. We studied a total of approximately 30 birds. For any specific vocalization the sample size was often smaller, particularly during the reproductive period when we concentrated on four pairs, although additional records were made of some other pairs. From November through April observations were made mainly at feeders, with the microphone placed within 1-3 m of the feeder. Two perches about 25 cm apart on each feeder enabled two birds to be on a feeder at the same time and encouraged interactions. We positioned ourselves about 10 m from the feeder and used 10 x 40 binoculars. From April to July birds were studied on territories in the 20-ha beech-maple forest. We followed individuals around their territories, but once the nest cavity was excavated we concentrated our activities near the nest hole. At that time, we often placed a microphone within 5-8 m of the nest hole. From August to October we followed flocks, and recorded their vocalizations. Most of the recordings were made with a Nagra III tape recorder at 7.5 ips and Sennheiser MKH 104 omnidirectional or 405 cardioid microphones, but we occasionally used a Uher 4000L tape recorder and Electrovoice 644 Soundspot microphone. While studying the birds, data on individual identity, behavior of the caller prior to and following the call, general context, and behavior of other birds in the vicinity prior to and following the vocalization were spoken into the microphone. Sonagrams were made using a Kay Sound Spectrograph 6061-B on intermediate (150 Hz) band setting. Classification and naming of displays poses some problems of when to split and when to lump. As 34 The Auk 95: