Long Island University-Post 1 article published in JoVE Behavior Probing the Limits of Egg Recognition Using Egg Rejection Experiments Along Phenotypic Gradients Lindsay Canniff1, Miri Dainson2, Analía V. López3, Mark E. Hauber2, Tomáš Grim4, Peter Samaš5, Daniel Hanley1 1Department of Biology, Long Island University-Post, 2Department of Animal Biology, School of Integrative Biology, University of Illinois, 3Departamento de Ecología, Genética y Evolución, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, 4Department of Zoology and Laboratory of Ornithology, Palacký University, 5Institute of Vertebrate Biology, Academy of Sciences of the Czech Republic This protocol provides guidelines for running egg rejection experiments: outlining techniques for painting experimental egg models to emulate the colors of natural bird eggs, conducting fieldwork, and analyzing the collected data. This protocol provides a uniform method for conducting comparable egg rejection experiments.