DOI: 10.5061/dryad.sn02v6xb5
title: Effects of nocturnal celestial illumination on high-flying migrant insects

description: Radar networks hold great promise for monitoring population trends of
 migrating insects. However, it is important to elucidate the nature of
 responses to environmental cues. We use data from a mini-network of
 vertical-looking entomological radars in the southern UK to investigate
 changes in nightly abundance, flight altitude, and behaviour of insect
 migrants, in relation to meteorological and celestial conditions. An
 abundance of migrants showed positive relationships with air temperature,
 indicating that this is the single most important variable influencing the
 decision to initiate migration. In addition, there was a small but
 significant effect of moonlight illumination, with more insects migrating
 on full moon nights. While the effect of nocturnal illumination levels on
 abundance was relatively minor, there was a stronger effect on the
 insects’ ability to orientate close to downwind: flight headings were more
 tightly clustered on nights when the moon was bright and when cloud cover
 was sparse. This indicates that nocturnal illumination is important for
 the navigational mechanisms used by nocturnal insect migrants. Further,
 our results clearly show that environmental conditions such as air
 temperature and light levels must be considered if long-term radar
 datasets are to be used to assess the changing population trends of
 migrants.
description: Two vertical-looking insect radars (VLRs) located at three sites
 in southern England between 2000 and 2009 collected insect abundance and
 flight behaviour data. One VLR was located at Rothamsted Research,
 Harpenden, Hertfordshire, for the whole 10-year period. The other VLR was
 at Malvern, Worcestershire, from 2000 to 2003 and then at Chilbolton,
 Hampshire, from 2004 to 2009. All statistical analyses were conducted in
 the R software environment (version 3.6.3).
description: # Effects of nocturnal celestial illumination on high-flying migrant
 insects
 [https://doi.org/10.5061/dryad.sn02v6xb5](https://doi.org/10.5061/dryad.sn02v6xb5) ## Description of the data and file structure In our research, we use data from a mini-network of vertical-looking entomological radars in the southern UK to investigate changes in nightly abundance, flight altitude, and behaviour of insect migrants in relation to the celestial conditions. This upload database contains three data files involved in the study; each data file corresponds to a section of the analysis, including the impact of the moonlight illumination on the number, flying height, and headings of the large and small migratory insects. Dataset1: **analysis of number vs variables.csv** It contains four sheets: 'large_spring': the related number analysis parameters for large insects in spring 'large_autumn': the related number analysis parameters for large insects in autumn 'med_spring': the related number analysis parameters for medium insects in spring 'med_autumn': the related number analysis parameters for medium insects in autumn X: The radar site name and sampling date number: the number of large or medium insects in each day over a radar site temp: ground-level temperature moon illumination percentage: percentage moon illumination (%) moon rise_hr: the hour of moon rising time season: sampling migratory season spring or autumn Dataset2: **analysis of heading vs variables.csv** It contains four sheets: 'large_spring': the related orientation analysis parameters for large insects in spring 'large_autumn': the related orientation analysis parameters for large insects in autumn 'med_spring': the related orientation analysis parameters for medium insects in spring 'med_autumn': the related orientation analysis parameters for medium insects in autumn X: The radar site name and sampling date number: the number of large or medium insects in each migration event over a radar site r.BA: the r value from the Rayleigh test for insect headings in each migration event which show common orientation p.BA: the p value from the Rayleigh test for insect headings in each migration event which show common orientation mean.BA: the mean value(degree) of the insect headings in each migration event which show common orientation, 0 is north, 180 is south moon illumination percentage: percentage moon illumination (%) moon rise_hr: the hour of moon rising time cloudcover rate: the cloud cover rate(%) season: sampling migratory season spring or autumn Dataset3: **analysis of height vs variables.csv** It contains four sheets: 'large_spring': the related flying altitude analysis parameters for large insects in spring 'large_autumn': the related flying altitude analysis parameters for large insects in autumn 'med_spring': the related flying altitude parameters for medium insects in spring 'med_autumn': the related flying altitude parameters for medium insects in autumn number: the number of large or medium insects in each migration event over a radar site moon illumination percentage: percentage moon illumination (%) cloudcover rate: the cloud cover rate(%) season: sampling migratory season spring or autumn