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Shedding light on light: benefits of anthropogenic illumination to a nocturnally foraging shorebird
Author(s) -
Dwyer Ross G.,
Bearhop Stuart,
Campbell Hamish A.,
Bryant David M.
Publication year - 2013
Publication title -
journal of animal ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.134
H-Index - 157
eISSN - 1365-2656
pISSN - 0021-8790
DOI - 10.1111/1365-2656.12012
Subject(s) - foraging , nocturnal , calidris , ecology , moonlight , full moon , cloud cover , biology , habitat , environmental science , geography , cloud computing , computer science , operating system
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 T ringa totanus ) overwintering on an industrialised estuary in N orthern E urope. 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.