Behavioural and Neurobiological Perception of Vocal Communication in Songbirds

• Author / Creator

  Scully, Erin N.

• Black-capped chickadees (Poecile atricapillus) are a species of North American songbirds commonly studied for their unique vocalizations. The two most studied vocalizations are their fee-bee song, used for mating and territory defense, and their name-sake chick-a-dee call, which has multiple functions including flock coordination, identifying food location, and mobbing of predators. While black-capped chickadees primarily produce fee-bee songs in spring, they produce chick-a-dee calls year-round with call production peaking in the fall. In Chapter 2 I asked if the meaning of the call may also change across seasons. For instance, flock communication could be more important in the fall than in the spring, and food type and availability change according to season. To determine if the chick-a-dee call varies acoustically across seasons in a predictable manner, I conducted an operant go/no-go discrimination task that examined black-capped chickadees’ ability to categorize calls produced in two different seasons: fall and spring. I found that birds trained to respond to vocalizations produced in either fall or spring learned to discriminate at the same rate as birds trained to respond to pseudorandomized stimuli. I also conducted a bioacoustic analysis of the calls and found no differences in calls produced in the spring versus calls produced in the fall. These results suggest that while chickadees can be trained to discriminate between chick-a-dee calls produced in different seasons, they do not discriminate these calls or perceive these calls as being members of natural, preexisting, perceptual categories, based on an underlying perceptual similarity. In Chapter 3, I expanded on a previous behavioural study that asked if chickadees have a preference for duty cycles (the proportion of time filled by vocalizations). Wilson and Mennill (2011) found that chickadees show stronger behavioral responses to playback of chick-a-dee calls with higher duty cycles. That is birds responded more to higher duty cycle playback compared to lower duty cycle playback. Here I presented chickadees with chick-a-dee calls with either high or low duty cycles, then measured the amount of ZENK labeled cells in the auditory nuclei. I found that there was no neurobiological difference between high and low duty cycles, differing from the previous behavioural results. Next, in Chapter 4, I conducted a methodology experiment. In large part due to its neuronal-specific labeling of ZENK protein, Santa Cruz Egr-1 sc-189 has been widely accepted as the standard primary antibody in songbird research. However, Santa Cruz Biotechnology Egr-1 no longer specifically labels and has also discontinued production of Egr-1 sc-189. Thus, Chapter 4 is focused on analyzing the effectiveness of alternative primary antibodies. Abcam monoclonal Egr-1 effectively labels ZENK in the songbird auditory nuclei, making it a suitable primary antibody replacement for Santa Cruz polyclonal Egr-1. Finally, in Chapter 5, I again aimed to replicate previous behavioural and bioacoustic studies to examine if chickadees attend to information regarding sex of the caller of the chick-a-dee call. Here I presented both male and female chickadees with altered chick-a calls (dee portion removed) of both sexes and measured the number of ZENK labeled cells in select auditory nuclei. I found that while there was no significant difference between male and female listeners, only calls produced by males had significantly more ZENK labeled cells than the control condition, with female produced calls not being significantly different from either of the two other groups. Overall, my thesis used multiple approaches to further understand how black-capped chickadees perceive the chick-a-dee calls.

• Subjects / Keywords

  • Songbirds
  • Vocal Communication

• Graduation date

  Spring 2020

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/r3-8wrn-fc37

• License

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