Results

Koen Hufkens

Brief overview of model analysis results, dynamically rendered as website output using the open data. The full files are presented in the analysis folder.

Moonlight flight height responses

Multi-data logger results (Table 1)

# read the data
df <- readRDS(here::here("data/curated/data_MDL.rds"))

# fit the model
fm_lagged <- glmmTMB::glmmTMB(
  altbin ~ moon_illuminance + lag_altitude + species + (1|species/tag),
  data = df,
  family = binomial
)

# report statistics of Table 1
print(summary(fm_lagged))

##  Family: binomial  ( logit )
## Formula:          
## altbin ~ moon_illuminance + lag_altitude + species + (1 | species/tag)
## Data: df
## 
##      AIC      BIC   logLik deviance df.resid 
##  35953.3  36016.4 -17969.6  35939.3    60881 
## 
## Random effects:
## 
## Conditional model:
##  Groups      Name        Variance  Std.Dev. 
##  tag:species (Intercept) 9.549e-01 0.9771959
##  species     (Intercept) 1.613e-07 0.0004016
## Number of obs: 60888, groups:  tag:species, 23; species, 3
## 
## Conditional model:
##                           Estimate Std. Error z value Pr(>|z|)    
## (Intercept)               -0.51356    0.36989   -1.39  0.16500    
## moon_illuminance           8.90868    0.26969   33.03  < 2e-16 ***
## lag_altitude               1.97752    0.02047   96.59  < 2e-16 ***
## speciesapus_pallidus      -1.77630    0.52346   -3.39  0.00069 ***
## speciestachymarptis_melba -4.27890    0.49564   -8.63  < 2e-16 ***
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1

GPS based results (Table 2)

# read the data
df <- readRDS(here::here("data/curated/data_GPS.rds"))

# fit the model
fm <- glmmTMB::glmmTMB(
  altbin ~ moon_illuminance + species + (1|species/tag),
  data = df,
  family = binomial
)

# report the statistics of Table2
print(summary(fm))

##  Family: binomial  ( logit )
## Formula:          altbin ~ moon_illuminance + species + (1 | species/tag)
## Data: df
## 
##      AIC      BIC   logLik deviance df.resid 
##   1631.0   1658.4   -810.5   1621.0     1775 
## 
## Random effects:
## 
## Conditional model:
##  Groups      Name        Variance  Std.Dev. 
##  tag:species (Intercept) 3.357e-01 0.5793967
##  species     (Intercept) 8.335e-09 0.0000913
## Number of obs: 1780, groups:  tag:species, 11; species, 2
## 
## Conditional model:
##                      Estimate Std. Error z value Pr(>|z|)    
## (Intercept)           -2.1526     0.3992  -5.392 6.96e-08 ***
## moon_illuminance      15.3049     1.0566  14.485  < 2e-16 ***
## speciesapus_pallidus   0.2165     0.4509   0.480    0.631    
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1

The above model responses are well captured visually in Figure 4 of the main manuscript, as shown below.

Figure 4. Marginal effect sizes by species for the generalised linear mixed effects logistic models relating moon luminance with flight height for both MDL, i.e. showing the probability of a high nighttime flight relative to daytime flight altitudes for MDL (a) and GPS (b). Grey 95% Confidence Intervals (CIs) were computed using a Wald z-distribution approximation and a standardised dataset.

Twilight dynamics

MDL based flight timing (Table 3)

# read the data
df <- readRDS(here::here("data/curated/data_twilight.rds"))

fm <- lme4::lmer(
  twilight_timing ~ moon_illuminance + (1|species/tag),
  data = df
)

# return twilight statistics
print(summary(fm))

## Linear mixed model fit by REML ['lmerMod']
## Formula: twilight_timing ~ moon_illuminance + (1 | species/tag)
##    Data: df
## 
## REML criterion at convergence: 51826
## 
## Scaled residuals: 
##     Min      1Q  Median      3Q     Max 
## -3.0770 -0.6582 -0.0225  0.6765  4.0411 
## 
## Random effects:
##  Groups      Name        Variance Std.Dev.
##  tag:species (Intercept)  13.576   3.685  
##  species     (Intercept)   2.056   1.434  
##  Residual                188.241  13.720  
## Number of obs: 6410, groups:  tag:species, 23; species, 3
## 
## Fixed effects:
##                  Estimate Std. Error t value
## (Intercept)         8.558      1.150    7.44
## moon_illuminance  129.888      8.039   16.16
## 
## Correlation of Fixed Effects:
##             (Intr)
## moon_llmnnc -0.094