Graduate Program
Biological Sciences
Degree Name
Master of Science (MS)
Semester of Degree Completion
Spring 2024
Thesis Director
Eric K. Bollinger
Thesis Committee Member
Paul V. Switzer
Thesis Committee Member
Scott J. Meiners
Abstract
During the winter months in Charleston, Illinois, thousands of American crows (Corvus brachyrhynchos) gather together each night to roost. While aspects of this impressive sight have been studied elsewhere, there is very limited information on how crows behave at night. Additionally, the mechanics and origins of communal roosting are not especially well understood, and the behaviors involved are not always consistently described. This study sought to provide a more complete assessment of crow communal roosting after sunset. I collected data between 2018 and 2020 by locating communal roosts and conducting continuous observations for 4 hours after sunset, with additional checks at 8 and 12 hours after sunset. Crows were found to be active and roosts mobile long after dark, though there was commonly a decrease in activity around 1 hour after sunset. When taking flight, the average direction of travel was more oriented towards the final roost during the 15 minutes prior to the final departure, and if crows were disturbed from their roosts they became less likely to change trees. By 8 hours after sunset, crows roosted more tightly and in fewer trees. Their final roost trees were not found to differ from the nearest unused trees, yet there is some evidence that crows may show a preference for specific areas rather than particular trees. In this thesis I discuss my findings with regards to the mechanisms by which groups may make decisions and the leading hypotheses on the origin of communal roosting. I also discuss potential knowledge gaps and opportunities for additional research.
Recommended Citation
Mrowiec, Caitlin M., "Nocturnal Behavior of Communally Roosting American Crows (Corvus brachyrhynchos)" (2024). Masters Theses. 5039.
https://thekeep.eiu.edu/theses/5039
