Table 3.

Parameter estimates, associated standard deviation, Z value, and p value of the selected mixed‐effects logistic regressions for variation in (a) probability of giving birth to a foal surviving to late summer and (b) probability of weaning a foal (survival to year t + 1)

Model variable	Estimate	SD	Z‐value	Pr(>|z|)	Odds ratio	OR‐LL	OR‐UL
(a) Probability of giving birth to a foal surviving to late summer
Intercept	−1.05	0.55	−1.92	0.055	0.35	0.12	1.02
Quality	0.06	0.13	0.44	0.662	1.06	0.82	1.38
Repro t − 1 (Yes)	−0.84	0.25	−3.40	0.001	0.43	0.27	0.70
Female age, first‐order polynomial	−2.03	3.75	−0.54	0.589	0.13	0.00	206.00
Female age, second‐order polynomial	−10.80	3.22	−3.36	0.001	0.00	0.00	0.01
Density	0.36	0.09	3.87	<0.001	1.43	1.19	1.71
Band size	0.17	0.05	3.67	<0.001	1.18	1.08	1.29
Band sex ratio	2.31	0.82	2.82	0.005	10.10	2.02	50.20
Quality: Repro t − 1 (Yes)	0.39	0.20	1.90	0.057	1.47	0.99	2.20
Female age, first‐order polynomial: Repro t − 1 (Yes)	−0.79	6.58	−0.12	0.904	0.45	0.00	1.79E+05
Female age, second‐order polynomial: Repro t − 1 (Yes)	15.89	5.41	2.94	0.003	7.96E+06	197.00	3.22E+11
(b) Probability of weaning
Intercept	3.91	1.07	3.65	<0.001	49.70	6.12	404.00
Quality	0.91	0.26	3.57	<0.001	2.49	1.51	4.10
Female age, first‐order polynomial	−18.60	5.59	−3.33	0.001	8.33E−09	1.47E−13	4.74E−04
Female age, second‐order polynomial	−5.16	3.18	−1.62	0.105	0.01	1.13E−05	2.92
Density	−0.50	0.14	−3.46	0.001	0.61	0.46	0.81
Band size	−0.22	0.08	−2.65	0.008	0.80	0.68	0.95
Band sex ratio	−2.58	1.41	−1.82	0.068	0.08	4.77E−03	1.21
Winter t + 1	−0.95	0.24	−3.88	<0.001	0.39	0.24	0.63
Intercept	3.91	1.07	3.65	<0.001	49.70	6.12	404.00

Horse identity was included as a random factor in all models. t refers to the focal year (i.e., foal birth year). Odds ratio, odds ratio lower level (“OR‐LL”), and odds ratio upper level (“OR‐UL”) are also presented. See text for details about variables.