Table 2.

Results of an ordinal regression model showing the effect of nest walls, egg weight and nest attendance, as well as their interactions, on reducing the number of eggs falling out of nests. Each bird experienced three treatments (n = 18; T0: nests without walls and light eggs, T1: nests without walls and heavy eggs, T2: nests with walls and light eggs) and we provided each of them with four eggs in the same weight in each experimental trial. The intercepts (i.e. x | x + 1, x = 0–3) represent the log of odds of x egg(s) dropped versus x + 1 eggs dropped. Values in the table indicate coefficients, standard errors (s.e.), t values, 2.5 and 97.5% confidence intervals and p-values, respectively. Bold p-values indicate statistical significance.

	coefficient	s.e.	t value	2.5%	97.5%	p-value
T1 (egg mass)	−2.704	0.861	−3.140	−4.392	−1.016	0.002
T2 (nest wall)	−18.474	<0.001	−1.136*106	−18.474	−18.474	<0.001
attendance	6.501	3.363	1.933	−0.091	13.093	0.053
attendance*T1	39.225	8.292	4.730	22.973	55.476	<0.001
attendance*T2	−92.522	<0.001	−1.008*1010	−92.522	−92.522	<0.001
0|1	0.886	0.606	1.464			0.143
1|2	1.896	0.540	3.512			<0.001
2|3	2.454	0.539	4.553			<0.001
3|4	2.982	0.557	5.358			<0.001