I am trying to use the functions suggested in the nest survival chapter of the Gentle Intro to generate a stage specific model of nest survival (2 stages, egg and nestling). I’m getting bizarre results and would like some input. I searched the forum and found some potentially helpful things, but so far, I’m still stuck.
For each nest record, “i” is the initiation of egg laying. I have an Age covariate denoting the negative age of each nest on the first day of the nesting season which allows me to model age related effects using the Add(age,0)… Add(age,n) function. Because we know hatching date very accurately and there is some variation around the 17-18 day mean incubation period length, I included a calculated covariate (HtchDay) for the age of the nest at hatching (generally 17 or 18, but including a few shorter and longer intervals). I then used the combined function ge(Add(age,n),HtchDay) to create a dummy variable where 1 = nestling stage. My nest season is 146 days long from first initiation to last fledge, so my DM includes 145 parameters.
I ran the model S = B0 + B1xstage and my results included B0 = 18.809 and B1 = -15.781, but no standard errors for either. So I get survival of 1 during egg stage, survival of 0.954 in nestling stage, and no error.
Can anyone enlighten me as to what (probably simplistic)mistake I’m making?
Thanks
Pru