I am interested in the relationship between body mass and thyroid hormones in male and female birds. I have a sample size of 77 males and 28 females. Of these individual, 6 males and 1 females were measured more than once. Initially I was going to examine the relationship between thyroid hormones and body mass in males and females using separate mixed effect models for each sex with bird ID as a random factor to control for repeated measures, but is it appropriate considering so few individuals have been sampled more than once? Or, is it better to randomly select one measure from the repeated sampling?
M1<-lmer(log10(Mass)~log10(TT3)+ (1|Band),REML=TRUE, data= THmassM)
It was recommended I look at sexes separately by a reviewer considering my sample size is skewed. Would a more appropriate model include sex as a predictor instead of examining males and females separately?