Which of these is a symptom of lead poisoning in birds?

Central nervous system disorders are a well-documented symptom of lead poisoning in birds. Lead interferes with the normal functioning of the nervous system, leading to a variety of neurological symptoms. Birds that have been exposed to lead may exhibit signs such as weakness, seizures, tremors, and even behavioral changes due to damage in the brain and nervous system. The accumulation of lead in the body can disrupt neurotransmitter functions, leading to these severe repercussions.

While the other choices mention symptoms that might occur in various health conditions, they are not specifically recognized as primary symptoms of lead poisoning in birds. Diarrhea and difficult breathing could arise from other illnesses or stressors, while flecks of red in mutes (feces) might not be directly linked to lead toxicity, making central nervous system disorders a clear indicator of lead exposure in avian species.