Chick-a-dee calls are common vocal signals in chickadees (Poecile spp.) that function in social organization. Earlier work indicated that the call is a structurally complex vocal system, in that it is open-ended and, theoretically, could convey a large amount of information. However, little quantitative empirical work has addressed whether signalers actually produce distinct chick-a-dee calls in different environmental or behavioral contexts. I tested this question in an eastern population of Carolina Chickadees (Poecile carolinensis). Calls were recorded from free-living birds, and contextual variables were noted at the time of call production. The structure of the chick-a-dee call—the average number of note types used in calls and the different categories of note composition used commonly by birds—was associated with a diverse set of variables, including the proximity of the signaler to the ground, the signaler's flight behavior and local population, and the presence of an avian predator. These results suggest that a receiver could gain considerable information about the signaler and its immediate environment from the different uses of note types in a signaler's calls. Furthermore, these findings support the notion, raised in earlier studies, that the chick-a-dee call is structurally and informationally complex.