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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