Researchers studying parental care in 20 female robins found that every female robin would place a recently collected worm into the first open mouth she saw in her nest. it appeared that the sight of an open mouth triggered the female bird's feeding behavior. to test this hypothesis, a robotic baby robin was added to every one of the 20 nests. the robot baby always had its mouth open, and the female robin always fed it first. we can conclude that

The correct answer is; the open mouth of a baby robin is seen as a sign stimulus for the female robin (parent), and that the open mouth is the impending cause for her behavior.

Robins build nests to protect their young from harm. Robins take care of their young by feeding them until they’re old enough to survive on their own.

Explanation:

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