Residual Deviance in Binomial GLM

Hello,
I am attempting to calculate the variation in many butterfly population sizes across 35 years of
monitoring. The data are in fractions, so I am using a binomial glm with a logit link function to look for
population trends across years. I was wondering if I could use the residual deviance output from the glm's
as a proxy of population variability? What are the issues associated with doing this? Thanks!
Josh

 		 	   		  
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