Tinbergen revisited: a replication and extension of experiments on the beak colour preferences of herring gull chicks

Young herring gull, Larus argentatus, chicks peck at the red patch on the lower mandible of their parent's yellow beak. In a famous study on the ‘instinctive behaviour’ of herring gull chicks, Tinbergen examined whether the presence, colour and position of the patch affected the pecking of the chicks. While this experiment is often cited as demonstrating a preference for a red patch, the original data showed that chicks pecked more at a black-patched model (Tinbergen 1948, De Levende Natuur, 51, 49–56). Tinbergen later ascribed this unexpected outcome to a methodological error in his experiment: the red-patched model was presented more frequently than all the others, which made him adjust his data later on. We repeated Tinbergen's experiment (experiment 1), using replicas of the original models. We also did the experiment as Tinbergen described it later on (but which he never carried out), presenting all models equally often (experiment 2). Our results confirm that red is not the most preferred colour when it is presented more often than other colours. In experiment 2 the relative ranking of all models was the same as in experiment 1, with the exception of the red-patched one, which was now preferred most, as expected by Tinbergen. Our findings also confirm that the more frequent exposure to the red model in experiment 1 resulted in a disproportionate decline in interest for this model. So, although he never did the actual experiment, Tinbergen's intuition and corrected data show a reasonable match to the results of our experiment.