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Table 4 Multivariable multi-level logistic regression model* estimating the associations between year, clutch number, fledglings in the brood, and hen’s age and the odds of survival among Eastern Loggerhead Shrike fledglings in a captive breeding program in Ontario (2006–2011)

From: Factors influencing mortality in a captive breeding population of Loggerhead Shrike, Eastern subspecies (Lanius ludovicianus ssp.) in Canada

Variable: OR 95 % CI P-value
Year of study (1–6): 0.40 0.29-0.56 <0.001
Clutch number:    
First clutch ref.   
2nd clutch 0.34 0.14-0.83 0.018
No. of fledglings in the brood: 1.74 1.20-2.54 0.004
Breeding female age (years):    
log(female's age) 37.00 3.04-451.01 0.005
(log(female's age))2 0.25 0.09-0.70 0.008
Random effects parameters: Variance 95 % CI <0.001
Pair ID 1.40 0.49-4.03  
Clutch ID 2.23 0.93-5.36  
  1. *Multilevel model includes random intercepts for clutch (Clutch ID) and breeding pair (Pair ID).
  2. Likelihood ratio test testing the significance of the random intercepts in the model.
  3. ref. = Referent category.