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Emitters and Receptors : Question 3
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The ethologist, Niko Tinbergen, studied the way adult gulls feed their young. The adult eats its food at sea. When the adult returns to its nest, the chick taps the side of the adult's beak. This tapping action causes the adult gull to open its mouth. The chick then places its head into its parent's mouth and the adult regurgitates some of its food for the chick to eat.

The beak of an adult gull is shown in the image below.





Tinbergen used different models to represent the beak of an adult gull. He showed each one in turn to a young gull chick to see if the tapping reaction occurred. The diagrams below show six of the models which Tinbergen used in his experiment.




The results of this experiment are shown in the table




Tapping response


No response



Answer the following questions


(a) What does the word regurgitate mean?


(b) Name two other types of bird which feed their chicks by regurgitating food.



(c) From the results of this experiment, what do you think is the stimulus which causes the chick to tap on the adult gull's beak? Give a reason for your answer.





(d) Does the shape of the beak have any influence on the chick's tapping reaction? Give a reason for your answer.





(e) How would you carry out an experiment to find out if the chick will tap beaks which have spots of other colours, such as red, blue and yellow? (You can use diagrams to help you answer this question).