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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.