Abstract
The use of artificial light at night (ALAN) is a rapidly expanding anthropogenic effect that transforms nightscapes throughout the world, causing light pollution that affects ecosystems in a myriad of ways. One of these is changing or shifting activity rhythms, largely synchronized by light cues. We used acoustic loggers to record and quantify activity patterns during the night of a diurnal bird – the common swift – in a nesting colony exposed to extremely intensive artificial illumination throughout the night at Jerusalem’s Western Wall. We compared that to activity patterns at three other colonies exposed to none, medium, or medium-high ALAN. We found that in the lower-intensity ALAN colonies swifts ceased activity around sunset, later the more intense the lighting. At the Western Wall, however, swifts remained active throughout the night. This may have important implications for the birds’ physiology, breeding cycle, and fitness, and may have cascading effects on their ecosystems.
Highlights
We have recorded a total of 26,373 files containing swift calls (Wall: 16,670, 12 nights; BI: 5,801, 11 nights; TLV: 3,827, nights; Desert: 75, nights)
This dramatic shift in activity patterns may have important and unknown implications for the swifts, as well as for their local ecosystem[11,12]
Summary
Study sites.We chose four breeding colonies for the study, differing in the level of ALAN they are exposed to. The study was performed at a late stage of the breeding cycle – after hatching and before fledging, when chick food consumption is at its peak This was done at all colonies concurrently between 07/05/2018 and 22/05/2018. 31°46′N, 35°14′E: an urban colony in Jerusalem’s old city composed of about 90 pairs. This is a Jewish religious site and is the country’s most visited site. 30°56′N, 35°03′E: a natural colony in a canyon cliff-face in a remote desert location This is a mixed colony of A. apus and A. pallidus, comprising of about 10–15 pairs of each species nesting in holes in the cliff facing roughly southwards. ALAN intensity: 0 lx (environmental measurement: 0.005 lx, the lowest, natural background light value, with no added artificial light)
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