Night Herons of Florida
Yellow crowns and black crowns add to Southwest Florida nightlife
The black-crowned night heron (Nycticorax nycticorax) and yellow-crowned night heron (Nyctanassa violacea) are the only two species of night herons found in Florida. Both species are more abundant in the lower two-thirds of the state. Both are rare in the Florida Panhandle. Black crowns are more abundant and widespread than yellow crowns in Florida and North America. In fact, black crowns are one of the most cosmopolitan herons, occurring virtually worldwide.
Determining accurate population estimates for these species is difficult as they are mostly nocturnal, exhibit secretive habits and nest below the canopy in freshwater and coastal marine wetlands that can be inaccessible. Even without firm population numbers, however, it is reasonable to assert that yellow-crown and black-crown populations have decreased over time as a result of shrinking feeding and nesting habitat. More than half of these freshwater and coastal marine wetlands have been destroyed since the turn of the century. Fortunately, in recent years wetland impacts have been reduced, and large areas of wetlands and their associated uplands are being managed and preserved through wetland mitigation banks. These large conservation areas help protect and enhance native feeding and nesting habitat that is critical to the well-being of night herons and other wildlife.
These two medium-sized night herons are easily differentiated from each other. The tops of the head and back of the adult black-crowned heron are black, and the sides of head, neck and belly are white. The wings and tail are light gray. The sexes are similar in appearance, though the female is slightly smaller. The iris of the eye is orange to crimson red and becomes more intense in color during breeding.
The adult yellow-crowned heron has a white to yellow crown and an elongated white patch on the sides of the head behind the eye. The bill and the rest of the head are black. The plumage is mostly blue-gray with the feathers of the wings and back being slightly darker with light edges. The feet and legs are yellowish-green, and the iris of the eye is orange to scarletorange, becoming more intense during the breeding season. The sexes appear similar in both plumage and size.
The juvenile plumage of both species includes brownstreaked under parts and brown upper parts with white flecking. The legs and feet are light yellow. The juvenile black crown has a yellow bill, and during flight only the tips of the feet project past the tail. The juvenile yellow crown has a black bill, and in flight the feet and legs extend well beyond the tail. It also has orange eyes, whereas the juvenile black crown has yellow eyes.
Black crowns nest in a variety of habitats from December in South Florida to July in northern parts of the state. They are known to nest even in exotic Brazilian peppers (Schinus terebenthifolius) on coastal dredged-material islands. After pairing, the female accepts nest material from the male and builds a nest among multispecies heron colonies. Three to five light bluish-green 2-inch (52-mm) eggs are laid one to two days apart. The male and female both incubate the eggs, which hatch within 24 to 26 days. Nestlings fledge in 42 to 49 days. Yellow crowns are more tolerant of human activity and nest in parks and residential areas. They lay four to five light bluishgreen 2-inch (52-mm) eggs. Both sexes incubate the eggs 21 to 25 days, and the nestlings fledge in 25 days.
Both these night herons feed at night and in low-light conditions. They will also feed during the day, especially during nesting periods. Yellow crowns are more likely to be observed feeding during the day. Black crowns feed mostly on fish. They
vibrate their bills at the water surface to attract fish, but they also feed on insects, crustaceans, frogs, salamanders, bird eggs, young birds (ibis, herons, terns) and small mammals.
Yellow crowns feed mostly on crabs and crayfish but will also eat fish, insects, leeches and young birds. I have observed yellow crowns feeding on large ghost crabs (Ocypoda quadrata) on the beaches and mudflats on Sanibel. They have the interesting habit of taking off the legs of crabs and crayfish before they swallow these crustaceans. Black crowns do not exhibit this feeding behavior. Yellow crowns benefit ground-nesting shorebirds in Florida by eating ghost crabs, which are known to feed on shorebird nestlings.
William R. Cox has been a professional nature photographer and ecologist for more than 35 years. Visit him online at williamrcoxphotography.com.
IT IS REASONABLE TO ASSERT THAT YELLOW-CROWN AND BLACK-CROWN POPULATIONS HAVE DECREASED OVER TIME AS A RESULT OF SHRINKING FEEDING AND NESTING HABITAT.