Pigeons, mostly. They poop on everything and that accumulated poop can be a real health hazard. https://www.nyc.gov/site/doh/health/health-topics/pigeon.page h

Pigeons, mostly. They poop on everything and that accumulated poop can be a real health hazard. https://www.nyc.gov/site/doh/health/health-topics/pigeon.page https://www.nyc.gov/site/doh/health/health-topics/pigeon.pag... If you think birds don't poop a lot remember there are entire islands made of bird poop. https://www.atlasobscura.com/places/nauru https://www.atlasobscura.com/places/nauru