What is the primary source of contamination leading to zinc toxicity in aquatic birds?

The primary source of contamination leading to zinc toxicity in aquatic birds is often due to the ingestion of foreign bodies, such as coins. Aquatic birds can mistake shiny objects, like coins or other zinc-containing materials, for food and consume them. Once ingested, these materials can lead to zinc poisoning, which can cause a variety of health issues, including hemolytic anemia and renal damage.

Zinc is commonly found in metallic items, and its accumulation in the body from these foreign objects can reach toxic levels, particularly if the birds cannot efficiently eliminate it. This type of toxicity is particularly concerning because it can affect the overall health and survival of the affected bird species.

While other sources such as waterborne pathogens, contaminated feed, and heavy metals in sediments contribute to the overall health risks for aquatic birds, they are not as direct or immediate sources of zinc toxicity compared to the ingestion of contaminated objects.