The following is a nice review by Kaeli Swift, Ph.D., of a recently published research paper by Loma Pendergraft on vocalizations by American Crows around food; post submitted by Craig Gibson

Background on Loma: Loma is a graduate student working in John Marzluff’s lab at the University of Washington and studying crow communication and cognition. Loma earned his undergraduate degree in wildlife ecology at Oklahoma State University. Before he was admitted to the UW, he worked as a science teacher for Tulsa Public Schools.

Background on Kaeli: Kaeli Swift, Ph.D., while an undergrad at Willamette University (2005-2009), discovered that crows and other corvids, offered the perfect marriage of her prior ornithology interests, and she has been hooked on them ever since. In 2012, she was awarded a National Science Foundation Graduate Research Fellowship to pursue this passion as a graduation student at the University of Washington. As a Masters and Doctoral student (2012-2018), she dedicated herself to understanding what American crows do in response to dead crows, as well as what adaptive motivations might drive their response. Her research included both field-based projects observing wild crows, and non-invasive/non-lethal functional imaging studies aimed at understanding what was going on in the crow brain during these experiences. Currently, she is a Post-Doctoral researcher at the University of Washington studying the foraging behaviors of Canada jays in Denali National Park.

Here is Kaeli’s recap:

After three years of labor, findings by Loma Pendergraft and John Marzluff have been published in a new paper entitled: Fussing over food: factors affecting the vocalizations American crows utter around food.1

Generally speaking, if an animal vocalizes at a food source, it must incur some benefit from that vocalization that outweighs the potential costs.

  • Costs include things like getting your food stolen by a competitor or drawing the attention of predators.
  • benefits may consist of things like being able to share resources with your mate or kin, claiming ownership, or attracting other individuals to help you secure a food source away from another bird.

Loma conducted three experiments.

Experiment 1: he attempted to look for patterns in their vocal behavior by categorizing and quantifying the calls given around food of varying amounts.

Experiment 2: he ground-tested his ideas about how he was interpreting the calls from Experiment 1 by doing playback.

Experiment 3: he tested whether the different calls he had recorded had any effect on the listener’s ability to find the food.

To conduct these tests, Loma:

  • used wild crow pairs that he located all around Seattle.
  • he used a variety of sometimes hilarious disguises.
  • fed each pair three different amounts of food over the course of three trials:
  • 1 peanut, 5 peanuts, or a bountiful 25 peanuts.
  • he recorded their behavior before and after feeding them, and then,
  • used vocal analysis software to detect patterns in call structure.

What he found was that, unlike the grand reveal we were all hoping for, few clear patterns emerged from the data. When crows are around food, they give shorter calls than they did before, and their calls around only a single peanut are longer than when they are around a more substantial amount of food. But in all the other areas where you might expect some pattern to emerge; call rate, peak frequency, the number of syllables, etc., none did.

Literature cited

  1. Pendergraft LJ T and Marzluff JM. (2019).Fussing over food: factors affecting the vocalizations American crows utter around food. Animal Behaviour 150: 39-57
  2. Mates EA, Tarter RR, Ha JC, Clark AB, and McGowen KJ. (2014). Acoustic profiling in a complexly social species, the American crow: caws encode information on caller sex, identity and behavioural context. Bioacoustics24