When birds of a feather poop together: Excessive birds feces and algal blooms. Algal blooms deplete oxygen in lakes, produce toxins, and end up killing aquatic life in the lake. Researchers are tracing the role of bird feces, which are rich in phosphorus and nitrogen. Ref. Source 9f.
So, the birds what is essentially fertilizer into these bodies of water, algae blooms, and the lake slowly suffocates. And what is surprising the dropping fertilizer into a body of water that supports plant life is going to make those plants grow better? Great research. They should have asked me this question and saved the money on the research.