Shedding light on light: benefits of anthropogenic illumination to a nocturnally foraging shorebird. (27th November 2012)

• Record Type: Journal Article
• Authors: Dwyer, Ross G.; Bearhop, Stuart; Campbell, Hamish A.; Bryant, David M.
• Editors: Roulin, Alexandre
• Is Part Of: Journal of animal ecology. Volume 82:Number 2(2013:Mar.)
• Page Start: 478
• Page End: 485
• Publication Date: 2012-11-27
• Subjects: Artificial light -- DMSP/OLS -- foraging strategy -- moonlight -- shorebirds; Animal ecology -- Periodicals; 591.7
• DOI: 10.1111/1365-2656.12012
• Languages: English
• ISSNs: 0021-8790

Abstract

Summary: Intertidal habitats provide important feeding areas for migratory shorebirds. Anthropogenic developments along coasts can increase ambient light levels at night across adjacent inter‐tidal zones. Here, we report the effects of elevated nocturnal light levels upon the foraging strategy of a migratory shorebird (common redshank Tringa totanus ) overwintering on an industrialised estuary in Northern Europe. To monitor behaviour across the full intertidal area, individuals were located by day and night using VHF transmitters, and foraging behaviour was inferred from inbuilt posture sensors. Natural light was scored using moon‐phase and cloud cover information and nocturnal artificial light levels were obtained using geo‐referenced DMSP/OLS night‐time satellite imagery at a 1‐km resolution. Under high illumination levels, the commonest and apparently preferred foraging behaviour was sight‐based. Conversely, birds feeding in areas with low levels of artificial light had an elevated foraging time and fed by touch, but switched to visual rather than tactile foraging behaviour on bright moonlit nights in the absence of cloud cover. Individuals occupying areas which were illuminated continuously by lighting from a large petrochemical complex invariably exhibited a visually based foraging behaviour independently of lunar phase and cloud cover. We show that ambient light levels affect the timing and distribution of foraging opportunities for redshank. We argue that light emitted from an industrial complex improved nocturnal visibility. This allowed sight‐based foraging in place of tactile foraging, implying both a preference for sight‐feeding and enhanced night‐time foraging opportunities under these conditions. The study highlights the value of integrating remotely sensed data and telemetry techniques to assess the effect of anthropogenic change upon nocturnal behaviour and habitat use. Abstract : For the first time, satellite imagery is combined with telemetry data to reveal the effect of lighting on the timing and distribution of foraging opportunities in a wild animal. This is important since coastal development is increasing worldwide, yet the impact of the illumination of these areas on individual foraging strategies remains unknown.