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Table 3 Univariable multi-level logistic regression models* estimating the associations between breeding pair and clutch characteristics, breeding site, year, and cage type 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
Site:    
Carden ref.   
Dyer's Bay 1.86 0.49-7.15 0.364
Year of study (1–6): 0.36 0.24-0.53 <0.001
Clutch number:    
First clutch ref.   
2nd clutch 0.20 0.07-0.55 0.002
Cage type:    
Double ref.   
Triple 1.60 0.25-10.51 0.622
No. of fledglings in the brood 2.54 1.68-3.85 <0.001
No. of nestlings in the nest 2.07 1.38-3.09 <0.001
Birth year of breeding female 0.83 0.66-1.05 0.119
Birth year of breeding male 0.85 0.68-1.07 0.179
Breeding female age (years):    
log(female’s age) 27.49 0.98-767.55 0.051
(log(female’s age)) 2 0.19 0.05-0.74 0.017
Breeding male age (years) 0.80 0.63-1.02 0.068
Breeding outcome of female in previous year:    0.397
Double-clutched ref.   
Failed to breed 0.18 0.02-1.72 0.135
Hatched the prior year 0.43 0.05-3.68 0.443
Single clutch in year prior 1.16 0.30-4.45 0.832
Unpaired 7.54 0.09-654.40 0.375
  1. *Univariable multi-level models include one fixed effect and random intercepts for clutch (Clutch ID) and breeding pair (Pair ID).
  2. P-value from a Wald chi-square examining the statistical significance of the entire categorical variable.
  3. ref. = Referent category.