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Individual recognition is a social behavior that occurs in many bird species. A bird’s ability to discriminate among familiar and unfamiliar conspecifics is critical to avoid wasting resources such as time and energy during social interactions. Black-capped Chickadees (Poecile atricapillus) are able to discriminate individual female and male chick-a-dee calls, potentially male and female tseet calls, and male fee-bee songs. In the current study, we used an operant discrimination go/no-go paradigm to determine whether female and male chickadees could discriminate between fee-bee songs produced by individual female chickadees as well as test which song component(s) enable this discrimination. Birds trained on natural categories—the songs of different females—learned to respond to rewarded stimuli more quickly than birds trained on random groupings of female songs and were able to transfer this learning to new songs from the same categories. Chickadees were also able to generalize their responding when exposed to the bee note of the fee-bee song of rewarded individuals; they did not generalize to fee notes. Our results provide evidence that Black-capped Chickadees can use female-produced fee-bee songs for individual recognition. However, the acoustic features underlying individual recognition require further investigation.

No abstract

When anthropogenic noise occurs simultaneously with an acoustic signal or cue, it can be difficult for an animal to interpret the information encoded within vocalizations. However, limited research has focused on how anthropogenic noise affects the identification of acoustic communication signals. In songbirds, research has also shown that black-capped chickadees (Poecile atricapillus) will shift the pitch and change the frequency at which they sing in the presence of anthropogenic, and experimental noise. Black-capped chickadees produce several vocalizations; their fee-bee song is used for mate attraction and territorial defence, and contains information about dominance hierarchy and native geographic location. Previously, we demonstrated that black-capped chickadees can discriminate between individual female chickadees via their fee-bee songs. Here we used an operant discrimination go/no-go paradigm to discern whether the ability to discriminate between individual female chickadees by their song would be impacted by differing levels of anthropogenic noise. Following discrimination training, two levels of anthropogenic noise (low: 40 dB SPL; high: 75 dB SPL) were played with stimuli to determine how anthropogenic noise would impact discrimination. Results showed that even with low-level noise (40 dB SPL) performance decreased and high-level (75 dB SPL) noise was increasingly detrimental to discrimination. We learned that perception of fee-bee songs does change in the presence of anthropogenic noise such that birds take significantly longer to learn to discriminate between females, but birds were able to generalize responding after learning the discrimination. These results add to the growing literature underscoring the impact of human-made noise on avian wildlife, specifically the impact on perception of auditory signals.

Referential communication has been defined as the exchange of information regarding an object or event, but few studies have examined referential alarm calls in songbirds. In contrast, it has been well-supported that chickadees produce mobbing calls in response to predators that vary depending on the threat level posed, and the auditory brain areas of chickadees produce similar neural expression in response to predator calls and conspecific mobbing calls of the same threat level. This suggests that chickadees perceive these acoustically distinct vocalizations as similar, potentially as referent signals. In the current study, we trained 33 birds on an operant go/no-go discrimination task in which chickadees were presented with predator and mobbing calls of high- or low-threat. Following the first round of training, birds completed a second round with high- or low-threat calls and we predicted that birds would show transfer of training when contingencies (i.e., threat level regarding a species of predator) were the same between hetero- and conspecific vocalizations. However, high- and low-threat mobbing calls were not treated similarly to the corresponding predator’s calls. Our asymmetrical results may be due to the acoustic distinction between calls produced by two owl predator species, but we cannot make definitive conclusions about referential communication from this study. Nonetheless, we believe that this experiment was an important exploration of the perception of referential signal.