I am trying to complete a binomial GLMM but I don't think that the residuals look right when I compare them to the years. Is this too much of a pattern in the residuals?
My model looks like this: binary response ~ carbon + I(carbon^3) + nitrogen + class + (1|Year). In my model, carbon and nitrogen are scaled isotope values, and class is the age class of the animal. The years are between 2003 to 2011. I have tried adding interactions, transforming the isotope values, and fitting it as a glm. All of these haven't improved the fit. I am using glmer in R. How can I go about improving the model? Or do I need to?