Date of Award


Document Type

Restricted Thesis

Terms of Use

© 2005 Jennifer E. Johnson. All rights reserved. Access to this work is restricted to users within the Swarthmore College network and may only be used for non-commercial, educational, and research purposes. Sharing with users outside of the Swarthmore College network is expressly prohibited. For all other uses, including reproduction and distribution, please contact the copyright holder.

Degree Name

Bachelor of Arts



First Advisor

Timothy C. Williams

Second Advisor

Julie Hagelin


Light pollution associated with human societies is profoundly and increasingly transforming the spaces nocturnally migrating birds traverse. Avian collisions with illuminated communication towers are one conspicuous consequence of light pollution, and more subtle behavioral effects may be widespread. In this study, I used a mobile marine radar to examine the flight patterns of nocturnally migrating birds passing over Philadelphia, PA. The radar was moved between two sites close to a group of tall, illuminated communication towers and two distant reference sites. During spring and fall migrations of 2003 and 2004, nocturnally migrating birds altered their flight paths near the towers. Specifically, some migrants actively avoided the illuminated towers under high visibility conditions, but congregated near the towers and flew in arcs and circles under low visibility conditions. These results are consistent with previous studies of avian behavior near illuminated structures and indicate that artificial night lighting substantially affects the behavior of nocturnally migrating birds.