Black-crowned Night Heron

Seen by day, these chunky herons seem dull and lethargic, with groups sitting hunched and motionless in trees near water. They become more active at dusk, flying out to foraging sites, calling "wok" as they pass high overhead in the darkness. Some studies suggest that they feed at night because they are dominated by other herons and egrets by day. A cosmopolitan species, nesting on every continent except Australia and Antarctica.