by Savrina Salartash (CLAS ’23, B.S.C.)
This month, I led a discussion in our lab meeting of the study by Scully et al. (2020) about variation in chick-a-dee calls produced in different seasons. My goal in reading and presenting this paper was to gather insight as to how I can conduct a similar research project with my own questions in mind.
Scully et al. focused on black-capped chickadees in Alberta, Canada. The research team aimed to determine whether there was variation in the chick-a-dee call of the chickadees across seasons, particularly focusing on the spring and fall. Are the birds able to discriminate between the fall and spring calls? Scully et al. concluded that there was no distinct difference between the calls in the spring and the fall. Their findings can potentially lead the Curry Lab to conduct similar research to come to conclusions regarding the receptiveness of call variation between chickadees of different ancestry genotypes.
The chick-a-dee call is made up of four note types and has more complexity than the song. The four notes, A, B, C, and D, always occur in the same order even though the composition and number of each note may vary. This call communicates threat, aggression, or community cohesion for a specific purpose, often regarding food or mobbing a predator. We do not know if there is a difference in the message being communicated in a chick-a-dee call from the fall or the spring. We also do not know whether there is a difference in the call itself that communicates such information. The researchers aimed to find out if there is a difference in the chick-a-dee call in the fall versus in the spring. They also wanted to know whether chickadees can categorize the calls into their respective seasons, which would indicate that there are differences in meaning being communicated by a difference in call.
Scully et al. housed 18 chickadees in operant chambers, unlike in the Curry Lab where members observe chickadees in their natural habitat. The room was on a light-dark schedule according to the light-dark schedule of the location. All 18 birds were captured in January and February of 2016 and were at least 1 year old at that time. The birds had access to water, grit, and cuttleworm as often as they pleased while being housed in the lab. The researchers also gave them one superworm twice daily to supplement their diets. A chickadee’s correct response to the discrimination task was directly correlated to their food allocation.
The chambers housing the chickadees included motor-driven feeders. Infrared cells on both the feeder and the request perch closest to it told researchers where the bird was positioned. A speaker inside the feeder played a black-capped chickadee call as stimulus, either recorded in the fall or in the spring. There were 250 calls total, 140 produced and recorded in the fall and another 110 in the spring. Background noise was eliminated from all stimuli recordings.
Scully et al. trained the 18 birds to obtain food using the request perch and the feeder, then trained them to respond correctly to the stimuli. This was called “pre-training,” where the birds became accustomed to their living environment and the stimuli they would be responding to during the experiment. The chickadees were observed in their response to the stimuli during discrimination training, which occurred after pre-training. The procedure was the same, though instead of hearing all 250 stimuli, the birds would only hear 120. The birds were rewarded with food and light if they responded correctly to the fall or spring stimuli. They would receive food and light by remaining on the perch to hear all of the stimuli play.
Ultimately, the data of Scully et al. did not indicate that black-capped chickadees naturally categorize fall and spring calls, though the birds can be trained to discriminate between these calls. Chickadees used rote memorization to learn the discrimination task rather than categorizing the stimuli by season. The researchers also found no distinct differences between the fall and spring call production. The only difference could be the number of notes produced, but this is not significant enough information to say that it is a seasonal difference. The birds used in the experiment seem to be responding to their training more than natural categorization of calls into the two seasons. Scully et al. concluded that a lack of variation between fall and spring chick-a-dee calls must be the reason why the birds did not categorize them as such. The research team plans to further investigate this information as it relates to black-capped chickadees due to the understanding that behavior and hormone levels change between seasons.
Our lab group discussed the Scully et al. paper in December 2021. We were most curious about the research methods and chickadee responses to stimuli. This appears to be a psychology-based study, which is different from what we do. We found the capture aspect of it to be interesting to us, since we do not capture and house chickadees but rather perform experiments and observations in the wild. We had an impactful discussion regarding how we could incorporate a similar experiment into our own research by altering the methodology slightly and answer the questions we would like to explore regarding chickadee calls.
This information could be useful to us in our future endeavors, though the methodology is quite different from the typical research of the Curry Lab. My research in particular could benefit from this type of research indicated in the Scully et al. paper. I am interested in quantifying the D note variation between Carolina chickadees, black-capped chickadees, and their hybrids. My future endeavors include looking into responses between species, taking into account the quantitative variation between their D notes. Scully et al. can help me to understand what goes into the planning of an experiment involving playback and response, since I am planning to conduct a response experiment of my own. There are several lab members working on playback and behavior experiments, and I plan to incorporate response and acoustic variability into such investigations.
Scully, E. N., K. A. Campbell, J. V. Congdon, & C. B. Sturdy. (2020). Discrimination of black-capped chickadee (Poecile atricapillus) chick-a-dee calls produced across seasons. Animal Behavior and Cognition 7: 247-256. doi: https://doi.org/10.26451/abc.07.02.14.2020