Table 1 Binomial GLMM summary describing the probability of migration departure with respect to weather conditions experienced during the 3 days preceding departure and the departure day

Intercept

 − 4.97 [− 7.49, − 2.44]

1.69

14.92

1

0.001

Crosswind

 − 0.27 [− 1.08, 0.53]

0.41

0.45

1

0.503

Wind speed

0.68 [− 018, 1.55]

0.44

2.38

1

0.120

Tailwind

1.41 [0.75, 2.07]

0.34

17.57

1

 < 0.0001

Air pressure

0.5 [− 0.54, 1.55]

0.53

0.89

1

0.345

Humidity

 − 0.51 [− 1.30, 0.28]

0.4

1.6

1

0.205

Cloud cover (medium)

 − 0.53 [− 1.85, 0.80]

0.68

0.6

1

0.438

Cloud cover (high)

 − 0.11 [− 0.57, 0.35]

0.23

0.22

1

0.634

Cloud cover (low)

 − 0.4 [− 1.64, 0.83]

0.63

0.41

1

0.523

Temperature

0.96 [− 0.28, 2.19]

0.63

2.31

1

0.128

Rain

0.19 [− 0.42, 0.79]

0.31

0.36

1

0.548

Colony (Margherita di Savoia)

3.09 [0.28, 5.91]

1.43

7.03

2

0.031

Colony (Molentargius)

0.57 [− 0.28, 3.42]

1.45

7.03

2

0.695

Year (2016)

 − 0.14 [− 2.24, 1.97]

1.07

0.017

2

0.898

Year (2017)

 − 0.17[− 3.40, 3.07]

1.65

0.017

2

0.919

Sex (Male)

 − 0.36 [− 1.54, 0.83]

0.6

0.347

1

0.555

Hours before sunset

4.37 [2.34, 6.41]

1.04

17.78

1

 < 0.0001

Hours before sunset²

 − 2.52 [− 3.89,  − 1.14]

0.7

12.87

1

0.0003