VAN WETTEN JCJ & VAN WETTEN SV (2022) Day and night activity of foraging Eurasian Spoonbills Platalea leucorodia. LIMOSA 95 (4): 188-195.
In spring and summer 2020 and 2021 observations on foraging
Eurasian Spoonbills were made in the Netherlands, during
daylight, civil twilight, and at night. We found that Spoonbills
commonly forage also during twilight and darkness (Tab. 1).
In intertidal areas, prey-intake rates decreased with lower
light intensity (Tab. 2), but chasing behaviour (indicating
presence of fish as prey) increased with progressing twilight
and darkness (Tab. 3). It is concluded that Eurasian Spoonbill
increasingly search for fish in twilight and darkness, possibly
by more frequently neglecting lower caloric value preys such
as Brown Shrimp Crangon crangon. In this way European
Spoonbills might maximise total energy intake despite lower
prey-intake rates during twilight and in the night. Lower
fish escape behaviour with decreasing light intensity is
reasoned to be the main factor explaining this diet switch. In
freshwater areas, where only fish are available as prey, prey intake rates increased after sunset. For breeding Spoonbills, foraging during night seems as
important as during the day. Other studies report sex-specific
patterns in foraging activity with males foraging during the
night and females during the day. This is possibly related to
the larger size and thus better capabilities to capture fish in
deeper waters by males.
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