Over the last 50+ years, American Crow populations have increased in urban areas in the United States, taking advantage of abundant food sources and protection received under the Migratory Bird Treaty Act. However, heightened urbanization is correlated with increased anthropogenic noise, which can negatively impact bird communication. Some avian species compensate for this by increasing their call frequency to improve sound transmission. Previous work has also shown that avian social behavior can vary with urbanization, with individuals displaying increased boldness in more urban environments. In this study, we assessed the vocalizations, number of approaches per crow, latency to respond, and closest approach of groups of American Crows in response to a predatory owl decoy and playback of a distressed crow call, across an urban gradient in Western Washington. To quantify urbanization, we scored aerial photographs of each site, assessed levels of pavement, vegetation, building cover, and water, and used principal component analysis to create an urbanization score. Analysis of the first 12 sample sites revealed no statistically significant relationship between behavior or the frequency of vocalizations against urbanization. Surprisingly, ambient noise did not vary across our urbanization gradient, so our lack of significant findings may be the result of decreased anthropogenic noise due to the Covid-19 shutdown. However, we did detect a significant negative relationship between average pause duration, the spans of silence between separate calls, and urbanization, so crows may have adapted to produce more predator-related calls in the once noisier urban areas. We have increased our sample size to 31 sites and are currently continuing our analysis. Understanding how human impacts on the environment influence how wildlife responds to threats is important given the continuous expansion of urban areas. Our results may aid with ecologically-focused urban planning and urban wildlife efforts.

Steller's Jays (Cyanocitta stelleri) emit multiple call types. Variation within and between call types could indicate a sophisticated method of vocal communication. Variation could also indicate different selective geographic pressures or learned regional dialects. It is currently unknown whether Steller's Jays have geographic variation in their calls. In this study, I investigated whether the 'wah call' of Steller's Jays varies between and within geographic regions. I analyzed recordings of 'wah calls' from two geographic regions spanning from Canada to Mexico. I quantified the number of syllables, the syllable duration, the call duration, and the average silence between syllables. 'Wah calls' are highly variable, with durations from 0.41 to 10.00 seconds, one to eleven syllables with durations from 0.26 to 0.71 seconds, and gap (silence between syllable) durations from <.01 seconds to 0.67 seconds. Preliminary analysis shows no significant differences in these acoustic variables between Steller's Jays in the Marine West Coast Forest and Mediterranean California regions. I am currently increasing my sample size, beginning analysis of additional Steller's Jay call types, and expanding data analysis to five geographic regions. The presence of regional variation could indicate that Steller's Jays learn their different vocalizations. Learning vocalizations could be a sign of complex communication within Steller's Jays. 

Songbirds can learn different song dialects depending on their geographical location. Taxonomically, the American Crow (Corvus brachyrhynchos) is a songbird, but lacks a traditional ‘song’. Despite this, research suggests that crows do possess brain regions necessary for song learning and production. Unlike their songbird relatives, it is not understood whether American Crow populations learn regional call dialects. Using recorded crow calls from the online database, Xeno-Canto, I analyzed the acoustic properties of over 150 audio files across nine ecoregions of North America. Using the bioacoustics program Raven Pro 1.6, I am currently quantifying the lowest frequency, syllable number, syllable duration, and call duration for each call. Geographical differences in call structure, if detected, may indicate that crows learn regional dialects, or the differences may be the result of different selection pressures in each region.