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April 21, 2022

5:00pm 1100 TLSB

EcoEvoPub Seminar Series
UCLA, Dept of EEB

" Graduate Student Presentations "


Mars Walters

Department of Ecology and Evolutionary Biology, UCLA, Yeh Lab

Urban Dark-Eyed Juncos Defended Territories Less Aggressively during the COVID-19 Lockdown

Phenotypic plasticity is an important mechanism allowing wildlife to colonize and establish populations in novel environments. Because urban areas impose strong, novel selection pressures on wildlife, recently established populations may evolve rapidly, and extreme expressions of plastic traits may become fixed. Phenotypic plasticity is difficult to study in urban wildlife because urban environmental variables are challenging to isolate and manipulate experimentally. However, COVID-19 lockdowns created a natural experiment in which urban wildlife populations normally exposed to high levels of disturbance were released from stressors associated with human presence. We took advantage of this to measure the territorial aggression responses of resident dark-eyed juncos (Junco hyemalis) on UCLA’s urban campus in Los Angeles, California. Differences in expression of territorial aggression frequently appear between urban and wildland populations of many songbird species. What role might human disturbance play in these shifts? Would juncos on territory adjust their aggression response toward conspecific intruders when relieved from frequent encounters with humans? We quantified their aggression responses using simulated territorial intrusions and compared measurements to those taken in 2019. We found that the population overall displayed significantly reduced aggression responses compared to the same population in 2019. Furthermore, individuals trialed in both 2019 and 2021 showed significantly reduced aggression responses during 2021, demonstrating that individual birds maintain phenotypic plasticity in this trait. Due to the mutable nature of urban habitats, urbanized populations with behaviors divergent from wildland conspecifics may maintain behavioral plasticity to cope with temporary environmental fluctuations, such as changing patterns of human disturbance.

Host: EEB Graduate Students