"Chickens have highly developed communication skills. According to Dr. Gisela Kaplan, a professor at the University of New England, 'the voices of birds involve learned, complex vocalizations.' Researchers have identified more than thirty-one different call types with very specific meanings. Chickens use separate alarm calls, for example, depending on whether a predator is traveling by land or in the sky. Karen Davis of United Poultry Concerns describes numerous calls, including distress calls, nesting and mating calls, laying calls, threat calls, 'all clear' calls, contented calls, and contact calls. Davis comments that 'each rooster can recognize the crow of at least thirty other roosters, probably more.' Australian scientists recently discovered that some hens emit high-pitched sounds to signal they have found food. The more they prefer a particular food, the faster they 'speak.' " (Amy Hatkoff, The Inner World of Farm Animals [Steward, Tabori & Chang, New York, 2009], p. 40.)
The distinction between object and emotion calls is not clear from the text. Presumably, all calls point to objects in the fowls' environment. Some calls appear to point, also, to emotions being experienced by calling chicken--such as "distress" and "contented" calls. But even the "emotion" calls probably have less to do with the state of the animal's mind (if the animal could be said to have a state of mind) and more to do with the state of world in which the animal is situated.
At all events, I would think that all calls are located in or capable of being located in a chicken's mental map of the environment in which the chicken is located. It is not clear whether the chicken would be aware of the difference between (if such a difference can even be postulated) between its mental map of the world and the layout of the world that it views. So at the most basic level, the calls are signs that signify by pointing to a state of the real world. They are not obviously symbolic or symbol manipulation.