Black-Crowned Night-Heron (Nycticorax nycticorax) rookery at the National Zoo in Washington, DC. Many of these birds nest around the Bird House at the zoo. They fly to local water sources after dark to hunt for food.

http://nationalzoo.si.edu/Animals/Birds/Facts/FactSheets/fact-blknightheron.cfm
Black-Crowned Night-Heron RookeryBlack-crowned Night Heron NestsBlack-crowned Night Heron NestsBlack-crowned Night Heron NestsBlack-crowned Night HeronBlack-crowned Night HeronBlack-crowned Night HeronBlack-crowned Night HeronBlack-crowned Night HeronBlack-crowned Night HeronBlack-crowned Night HeronBlack-crowned Night HeronBlack-crowned Night HeronBlack-crowned Night HeronBlack-crowned Night HeronBlack-crowned Night HeronBlack-crowned Night HeronBlack-crowned Night HeronBlack-crowned Night HeronBlack Crowned Night Heron