Which chemical is known to cause aerial distress displays and works as a flock frightening agent?

Avitrol is recognized for its unique role as a flock frightening agent. It operates by inducing distress signals among targeted bird species, often prompting them to exhibit behaviors that can be observed as panic or alarm. This chemical is utilized in situations where bird populations need to be managed or discouraged from certain areas, particularly in agricultural settings or near airports.

When birds are exposed to Avitrol, they experience physiological effects that signal distress, which can cause the rest of the flock to react and leave the area. This is a key component of its effectiveness, as the goal is to create a deterrent effect that reduces damage caused by these birds.

The other chemicals listed—2,4-D and Dicamba—are primarily herbicides used for controlling unwanted vegetation and do not produce similar distress displays in birds. Their action lies in targeting plant systems, which is distinctly different from the flock alarming behavior associated with Avitrol. Therefore, the selection of Avitrol as the answer aligns perfectly with its designated purpose in managing bird populations through behavioral modification rather than direct toxic action on the birds themselves.