Date: January 23, 2019
Source: Morris Animal Foundation
Mockingbirds exposed to sub-lethal levels of lead in urban areas display significantly heightened aggression, said Morris Animal Foundation-funded researchers at Tulane University. The team said their findings highlight the possibility that sub-lethal lead exposure may be common among other wildlife living in urban areas and more work is needed to better understand its full effects. Their study was published in Science of the Total Environment.
"There's considerable lead contamination in soils around the world and that means literally billions of animals, both urban wildlife and pets, are likely exposed at sub-lethal levels," said Dr. Jordan Karubian, Associate Professor at Tulane University's Department of Ecology and Evolutionary Biology. "The levels aren't killing them, but they may affect their behavior or physiology. Heightened aggression among mockingbirds may just be the tip of the iceberg."
For the study, the team used simulated territorial intrusion on dozens of northern mockingbirds in urban New Orleans neighborhoods with either low or high levels of lead in the soil. Researchers placed a taxidermized mockingbird on a tripod, 25 feet away from nests that pairs of mockingbirds were constructing, a situation in which the birds act most territorial. The researchers also played recorded songs of singing males to alert the mockingbirds and make the intrusions more realistic.