Age-dependent survival and environmental covariates

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Age-dependent survival and environmental covariates

Postby sharrod » Mon May 27, 2019 6:52 pm

Hi,

I am estimating juvenile recruitment for a population of birds. My data consists of birds banded as chicks and those that survived and were recaptured in subsequent years. Accordingly, I created 2 age classes, young (chicks only) and adult (chicks that survived and were recaptured) using the code on C-61 of Appendix C of the Gentle Intro manual.

I also have a set of weather variables collected over the study duration, and I want to see which affect juvenile survival. To that end, I've created several single-covariate models using the following format:
Code: Select all
Phi.ONI=list(formula=~ONI_NBS:ya)


with ONI_NBS being a weather variable and ya being the age bins. However, when I compare these against my null (Phi~ya), the null comes out as my top model. I have 3 other sites I'm running this analysis on and I've had the same result for each. I've estimated adult survival before and found that weather has an effect, so based on that (and previous studies) I find it hard to believe that weather has no effect on juvenile survival anywhere. I've looked through Appendix C, but there are no example (that I could find) looking at environmental covariate effects on 1 group.

Any help or clarification would be appreciated.
sharrod
 
Posts: 10
Joined: Thu Aug 24, 2017 12:05 pm

Re: Age-dependent survival and environmental covariates

Postby sharrod » Wed May 29, 2019 7:34 pm

From jlaake:

"I'm not surprised that your model was not as good. You have specified a model with 2 slopes but only a single intercept which is the same for young and adults. Use * instead of :"
sharrod
 
Posts: 10
Joined: Thu Aug 24, 2017 12:05 pm


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