The pronoun they is not vague. Select its one clear antecedent.
Nico Nijenhuis has created robotic falcons that are so lifelike that they scare off gulls and geese from airports, croplands, and dumps.
Nico Nijenhuis has created robotic falcons that are so lifelike that they scare off gulls and geese from airports, croplands, and dumps.
In this sentence, the clear antecedent of "they" is "robotic falcons."