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Table 1 Summary and parameterization of non-linear models (GAM, five- and six-parameter Double-Richards models) testing the temporal variation of numbers of the Shelduck wintering at Sabkha Djendli in northeastern Algeria

From: Are diurnal time-budgets and activity patterns density-dependent in the Shelduck (Tadorna tadorna) wintering in Algeria? An analysis across multiple temporal scales

Parametric coefficients

Estimate

Std. error

t-value

p value

Sig.

Generalized additive model ‘GAM’ (AIC = 363.2)

 Intercept

505

33.26

15.18

< 0.001

***

 Smooth term

Edf

Ref.df

F

p-value

Sig.

 s(10-day period)

6.75

7.86

19.88

< 0.001

***

Five-parameter Double-Richards model (AIC = 368.4)

 Asym

1733.8639

557.45

3.11

0.005

**

 K

0.5746

0.23

2.52

0.019

*

 Infl

8.5598

0.65

13.20

< 0.001

***

 RAsym

− 1758.0238

635.49

− 2.77

0.011

*

 RM

1.9059

1.39

1.37

0.184

ns

Six-parameter Double-Richards model (AIC = 366.1)

 Asym

1139.0003

221.26

5.15

< 0.001

***

 K

1.0588

0.51

2.10

0.048

*

 Infl

8.0153

0.51

15.85

< 0.001

***

 RAsym

− 1470.3866

791.61

− 1.86

0.077

ns

 Rk

0.3309

0.25

1.33

0.197

ns

 Ri

22.0231

2.55

8.64

< 0.001

***

  1. Asym, K, Infl, RAsym, RM, Rk and Ri are parameters of the positive–negative Richards model, see subsection: modelling temporal changes of wintering numbers
  2. AIC Akaike information criterion, Sig. statistical significance
  3. *** p < 0.001, ** p < 0.01, * p ≤ 0.05, nsp > 0.05