Glass buildings as bird feeders: urban birds exploit insects trapped by polarized light pollution

• Published in: Acta zoologica Academiae Scientiarum Hungaricae (Budapest, Hungary : 1994) Vol. 56; no. 3; pp. 283 - 293
• Main Authors: Robertson, B, Kriska, G, Horvath, V, Horvath, G
• Format: Journal Article
• Language: English
• Published: 01.01.2010
• ISSN: 1217-8837

Glass buildings can highly and horizontally polarize reflected sunlight and skylight, fooling polarotactic aquatic insects into thinking they are exaggerated water surfaces and high quality breeding habitat. We find that several urban generalist bird species are exploiting a caddis fly population caught by reflected polarized light. Daily patterns of European Magpie foraging behaviour indicate birds regularly visit a highly polarizing glass building to feed on attracted polarotactic caddis flies near sunrise and sunset. Foraging behaviours used by terrestrial land birds to collect caddis flies were typical of those used in more natural environments. This is the first example of exploitation of a species that is victim of polarized light pollution. Results demonstrate the ability of polarized light pollution to create novel predator-prey interactions, a phenomenon that may be a common and widespread occurrence where polarizing structures are built near freshwater. Because birds are consuming prey that will eventually experience reproductive and adult mortality associated with the polarized light trap, this scenario appears to represent a clear case of compensatory mortality.