Imprinting as an evolutionary strategy for learning egg recognition in brood parasitism

Signal detection and recognition play important roles in the interactions between animal species. In brood parasitism, some birds lay eggs in the nests of other species, leaving their offspring to be raised by the host birds. Because there is variation in the appearance of the host and parasitic eggs, host birds must learn to recognize and reject the parasitic eggs. Certain host species can "imprint" on their first brood, using those eggs as a template for identifying parasitic eggs in subsequent years. We use simple models of signal recognition and learning to understand why an imprinting mechanism may be evolutionarily advantageous compared to learning from every nest over time. Our results show that continued learning does not significantly enhance fitness after the first few nests. In addition, we calculate the information gained by hosts about their own egg distribution, showing that the first few nests provide far more information than later nests. Our results offer an information-theoretic perspective on why some host birds only imprint on their first brood. Our framework for studying signal recognition and learning can be applied to understand imprinting in other biological processes.