This relates to the concept of fixed action patterns because it is a series of actions one takes to completion (when an animal has an enate behavior of multi set behavior so once step A happens, the animal will go through B, C, etc until completion) The male robin cannot discriminate between real red male robins, and red feathers on a stick. For its history, it didn't need to evolve a better way to discriminate between real male robins and red feathers on a stick. Humans also show fixed action patterns. When we see someone and don't recognize them, we likely say how's it going and lift our heads and our eye brows. We don't even know we are doing it, but when someone does it to us, we do it back to them.
The trigger for this fixed action pattern is the red feathers, so now they have to complete this fixed action pattern. The grey lag goose is another example of a fixed action pattern. They protect their eggs in their nest so if they see one outside of their nest, they will pull it back into their nest. So if they see a ball outside of their nest, this will trigger the fixed action pattern and they will pull the ball into their nest as if it were an egg.
11th EditionLisa A. Urry, Michael L. Cain, Peter V Minorsky, Steven A. Wasserman 6th EditionDavid L Nelson, Michael M. Cox 2nd EditionDavid E. Sadava, David M. Hillis, H. Craig Heller