Lunar synchronization of daily activity patterns in a crepuscular avian insectivore.

Felix Liechti,Mihai Valcu,Gabriel Norevik,Tom Artois,Céline Kowalczyk,Anders Hedenström,Bart Kempenaers,Soddelgerekh Bayargur,Susanne Åkesson,Eddy Ulenaers,Ruben Evens,Batmunkh Davaasuren

doi:10.1002/ece3.6412

Abstract

Biological rhythms of nearly all animals on earth are synchronized with natural light and are aligned to day‐and‐night transitions. Here, we test the hypothesis that the lunar cycle affects the nocturnal flight activity of European Nightjars (Caprimulgus europaeus). We describe daily activity patterns of individuals from three different countries across a wide geographic area, during two discrete periods in the annual cycle. Although the sample size for two of our study sites is small, the results are clear in that on average individual flight activity was strongly correlated with both local variation in day length and with the lunar cycle. We highlight the species’ sensitivity to changes in ambient light and its flexibility to respond to such changes in different parts of the world.

Highlights

Natural light cycles, such as day-and-night transitions and the lunar cycle, have been consistent over geological timescales, providing a reliable set of environmental cues that have organized ecological systems and shaped evolutionary processes (Kronfeld-Schor et al, 2013, Gaston & Bennie, 2014; Swaddle et al, 2015)
We present an analysis of the lunar-associated behavior of European Nightjars (Caprimulgus europaeus; hereafter referred to as nightjar; Figure 1) by testing the hypotheses that the lunar cycle affects their nocturnal flight activity
We investigated this by analyzing daily activity patterns of individuals from three distinct parts of the species’ breeding range (Mongolia, Belgium and Sweden; Figure 2a), during two discrete periods of the annual cycle in relation to the lunar cycle, while controlling for variation in local day length

Summary

| INTRODUCTION

Natural light cycles, such as day-and-night transitions and the lunar cycle, have been consistent over geological timescales, providing a reliable set of environmental cues that have organized ecological systems and shaped evolutionary processes (Kronfeld-Schor et al, 2013, Gaston & Bennie, 2014; Swaddle et al, 2015). Wiacek, & Geiser, 1999) and high singing, reproductive and foraging activity around full moon (Brigham & Barclay, 1992; Holyoak, 2001; Jackson, 1985; Mills, 1986; Perrins & Crick, 1996) Despite these indications of population-level responses to the lunar cycle, variation in activity patterns at the individual level in relation to nocturnal light conditions have not yet been quantified, except in the context of thermoregulation (e.g., Smit, Boyles, Brigham, & McKechnie, 2011) and migration (Norevik, Akesson, Andersson, Backman, & Hedenstrom, 2019). We investigated this by analyzing daily activity patterns of individuals from three distinct parts of the species’ breeding range (Mongolia, Belgium and Sweden; Figure 2a), during two discrete periods of the annual cycle (the breeding and the nonbreeding season) in relation to the lunar cycle, while controlling for variation in local day length

| METHODS

Findings

| DISCUSSION