Atypical feeding of woodpeckers, crows and redstarts on mass-swarming Hydropsyche pellucidula caddisflies attracted to glass panes

Abstract

Artificial shiny dark objects reflecting horizontally polarized light (e.g. asphalt roads, black cars, solar panels) can attract polarotactic aquatic insects in mass. Glass buildings on the riverside also lure swarming caddisflies emerging from the river. These caddisfly swarms are a temporary rich food source for certain bird species, such as white wagtails (Motacilla alba), house sparrows (Passer domesticus), magpies (Pica pica) and great tits (Parus major). We report here about our observation of great spotted woodpeckers (Dendrocopos major), hooded crows (Corvus cornix) and black redstarts (Phoenicurus ochruros) feeding atypically on Hydropsyche pellucidula caddisflies swarming at glass buildings placed on the shore of the river Danube in Budapest (Hungary).