In today’s Academic Minute, Dr. Sara DeLeon of Drexel reveals how exposure to environmental pollutants can alter the performance of bird songs.
Sara DeLeon is a postdoctoral researcher in the Department of Biology at Drexel University in Philadelphia, Pennsylvania. DeLeon conducted the research project into PCBs and bird songs while earning her doctorate at Cornell University.
Dr. Sara DeLeon – How PCBs Alter Bird Songs
Polychlorinated biphenyls, or PCBs, are a group of 209 man-made chemicals. Last century they were used mainly as insulators in industry because they are so stable. Yet they were not disposed of properly and today they are well-know, worldwide chemical pollutants.
Decades of work has shown that PCBs encountered from the environment can be toxic and carcinogenic when encountered in high levels. But less is known about low-levels of PCB exposure. PCBs are environmental endocrine disruptors, meaning that even very low levels of PCBs could be mimicking the effects of hormones, and potentially influencing behavior.
We studied the effects of PCBs on birdsong, focusing on two common songbird species, black-capped chickadees and song sparrows, that occur in New York along the Hudson River, a region with extensive PCB pollution. We recorded their song, and we were able to take enough blood from each individual without killing them, to measure their PCB exposure.
Our results show that both species from regions with higher PCB pollution have more PCBs in their blood. But the two species differed in the amounts of the different 209 PCB molecules they had. The chickadees had a higher percentage of PCBs that tend to act more toxic, while the sparrows had a higher percentage of those that act more like hormone mimics.
The songs of chickadees and sparrows from PCB contaminated regions were different too. Black-capped chickadees from areas of PCB pollution sang less stereotyped songs, which is an important trait in species recognition. Song sparrows from contaminated regions performed trills that were directly predicted by the levels of certain PCBs in their blood, and overall their trill performance was better. These results show that the types of PCBs that the songbirds are encountering can influence song in different ways. And overall, this low level of PCB exposure appears to be having important behavioral effects on wild birds.