Fewer mockingbirds possible due to lead contamination

Lead contamination gets into the blood and feathers of mockingbirds and correlates with less effective nesting. Credit: Shutterstock

A groundbreaking study conducted by Tulane University reveals the potential impact of lead contamination on mockingbirds in urban environments, extending beyond its well-known risks to children. The study, which was published in Environmental Research, found a correlation between high lead levels in the soil and reduced nesting effectiveness in mockingbirds in New Orleans. Additionally, researchers discovered a direct link between soil lead levels and lead levels present in the blood and feathers of mockingbird hatchlings within their respective neighborhoods.

Unlike previous studies that focused on either extremely low or lethal levels of lead toxicity, the research conducted by the Karubian Lab at Tulane University delved into the effects of sublethal levels of lead. These levels of lead are significant enough to have an impact on the birds, yet not fatal.

Annelise Blanchette, a Ph.D. student in the lab who contributed to the study, explained, “We lack a fundamental understanding of how sublethal levels of lead affect the bodies, behaviors, physiology, and development of animals, as most research primarily looks at lead poisoning and the lethal dosages.”

Mockingbirds were chosen as the focal species for this study due to their widespread presence, making them easily accessible for research purposes. Their territorial behavior was also beneficial, as it allowed researchers to examine lead exposure with great precision. Lauren Hitt, the lead author of the study, who conducted the research as part of her undergraduate honors thesis at Tulane, proposed that nestling birds have the potential to serve as effective bioindicators, similar to the concept of a canary in a coal mine.

In investigating the impact of lead exposure on mockingbirds, the team aimed to identify potential aggression resulting from lead exposure. Lead has been known to cause social aggression in humans and animals, including mockingbirds. However, the specific impact of this aggression on various aspects of a mockingbird’s life, such as nest success and fidelity, remains largely undocumented.

Hitt stated, “We did confirm that one-third of the nests in our system had nestlings sired by multiple fathers, a phenomenon confirmed for the first time in mockingbirds. However, this extra-pair mating did not appear to be influenced by lead levels.”

On the other hand, nests in neighborhoods with lower levels of lead exhibited higher survival rates for eggs compared to nests in areas with higher lead concentrations. The study also identified other causes of egg and nestling mortality, including nest abandonment, nestling illness, and predation.

The research conducted by the Karubian Lab represents just the beginning of lead and urban wildlife exploration. Hitt and Blanchette emphasized how much remains unknown within the field, particularly as urban environments continue to expand and more animals interact with the stressors and heavy metal pollution associated with cities.

More information:
Lauren G. Hitt et al, Lead exposure is correlated with reduced nesting success of an urban songbird, Environmental Research (2023). DOI: 10.1016/j.envres.2023.115711

Provided by Tulane University

Citation: Lead contamination may mean fewer mockingbirds (2023, June 15) retrieved 15 June 2023 from https://phys.org/news/2023-06-contamination-mockingbirds.html

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