Table 2.
Temporal variation in nest initiation
| Response - # of initiated nests | Gaussian | Poisson | ||||||
|---|---|---|---|---|---|---|---|---|
| Model | Effect type | Effect | Estimate | 95% CI | Estimate | 95% CI | ||
| Complex | Fixed | Intercept | 0.943 | 0.64 | 1.247 | −0.302 | −0.591 | −0.02 |
| Spring tide cycle number | −0.195 | −0.325 | −0.065 | −0.236 | −0.375 | −0.105 | ||
| Cos (Day of spring tide cycle) | 0.105 | 0.002 | 0.208 | 0.096 | −0.016 | 0.202 | ||
| Sin (Day of spring tide cycle) | 0.043 | −0.09 | 0.174 | 0.038 | −0.103 | 0.176 | ||
| Cos × Spring tide cycle number | −0.06 | −0.163 | 0.041 | −0.048 | −0.168 | 0.069 | ||
| Sin × Spring tide cycle number | 0.016 | −0.122 | 0.147 | 0.019 | −0.127 | 0.168 | ||
| Random (variance) | First or second half : Spring tide cycle : Year (intercept) | 9% | 29% | |||||
| Spring tide cycle : Year (intercept) | 7% | 19% | ||||||
| Year (intercept) | 13% | 40% | ||||||
| Residual – Gaussian/Observation (intercept) - Poisson | 71% | 12% | ||||||
| Simple | Fixed | Intercept | 1.349 | 0.954 | 1.747 | 0.205 | −0.193 | 0.575 |
| Spring tide cycle number | −0.11 | −0.188 | −0.034 | − 0.138 | −0.216 | −0.059 | ||
| Cos (Day of spring tide cycle) | 0.104 | 0.001 | 0.211 | 0.033 | −0.114 | 0.171 | ||
| Sin (Day of spring tide cycle) | 0.04 | −0.098 | 0.17 | 0.108 | 0.002 | 0.214 | ||
| Random (variance) | First or second half : Spring tide cycle: Year (intercept) | 9% | 30% | |||||
| Spring tide cycle: Year (intercept) | 7% | 19% | ||||||
| Year (intercept) | 13% | 40% | ||||||
| Residual – Gaussian/Observation (intercept) - Poisson | 72% | 12% | ||||||
The posterior estimates (medians) of the effect sizes with the 95% CIs derived from a posterior distribution of 5000 simulated values generated by the ‘sim’ function in R. Variance components were estimated by the ‘lmer’ function in R. To account for non-independence of data points ‘Year’, ‘Spring tide cycle number’ within year and indication whether the nest was initiated in the ‘First or Second half’ of the spring tide cycle were fitted as random intercepts. Overdispersion was modelled by adding ‘Observation’ level as random intercept. ‘Spring tide cycle number’ is standardized within the year, so that the first spring tide cycle in the given year corresponds to the cycle when the first nest was initiated. ‘Day of spring tide cycle’ was transformed to radians (2 * number of days after the last spring tide * π/length of the given spring tide cycle [~ 14.75]) and fitted as sine and cosine of radians