Evaluating the effects of moonlight on the vertical flight profiles of three western palearctic swifts
Koen Hufkens, Christoph M. Meier, Ruben Evens, Josefa Arán Paredes, Hakan Karaardiç, Stef Vercauteren, Ann Van Gijsel, James W. Fox, Carlos Miguel Pacheco, Luis P. da Silva, Sandra Fernandes, Pedro Henriques, Gonçalo Elias, Luís T. Costa, Martin Poot, Lyndon Kearsley
Abstract
Recent studies have suggested the presence of moonlight mediated behaviour in avian aerial insectivores, such as swifts. Here, we use the combined analysis of state-of-the-art activity logger data across three swift species, the Common, Pallid and Alpine swifts, to quantify flight height and activity in responses to moonlight driven crepuscular and nocturnal light conditions. Our results show a significant response in flight heights to moonlight illuminance for Common and Pallid swifts, i.e. when moon illuminance increased flight height also increased, while a moonlight driven response is absent in Alpine swifts. We show a weak relationship between night-time illuminance driven responses and twilight ascending behaviour, suggesting a decoupling of both crepuscular and night-time behaviour. We suggest that swifts optimise their flight behaviour to adapt to favourable night-time light conditions, driven by light responsive and size-dependent vertical insect stratification and weather conditions.
You are required to cite both the Zenodo data repository as well as the BioRXiv pre-print when using the project data, please refer to the data as: Hufkens et al. Moonlight synchronous flights across three western palearctic swifts mirror size dependent prey preferences. https://doi.org/10.5281/zenodo.7814214, and Hufkens et al. Moonlight synchronous flights across three western palearctic swifts mirror size dependent prey preferences. bioRxiv 2023.04.25.538243; doi: https://doi.org/10.1101/2023.04.25.538243.
Use
Clone or download the project zip file.
git clone https://github.com/bluegreen-labs/swift_lunar_synchrony.gitThe repository is an R project and can be opened in RStudio, which will set the correct relative path.
Data structure & analysis
Analysis data is saved as compressed R serial files (.rds) in the data folder. Scripts to reproduce the main statistical results are provided in the analysis folder. Data contain the below fields:
| Variable | Description |
|---|---|
| tag | tag id of the data logger used (alpha-numeric) |
| species | swift species |
| lag_altitude | lagged altitude to account for correlations in the residuals of models |
| moon_illuminance | moon illuminance (in lux) |
| moon_phase | moon phase (descriptive) |
| stages | stages of the day (day, dawn, dusk, night) |
| altbin | Altitude bin, if data is low or high (0, 1) |
Related work
This study is follow up work of our paper in Oikos titled: “The aeroecology of atmospheric convergence zones: the case of pallid swifts”. You can find this dataset on Zenodo here