Black Skimmer With its unique bill and foraging behavior, the Black Skimmer ( Rynchops niger ) is one of the most interesting and distinctive of our coastal waterbirds. Skimmers are black above and white below and have long narrow wings, but it is their bill that readily distinguishes them from other members of the order Charadriiformes. The basal half of a skimmer’s bill is bright red and the distal end black. The bill is laterally compressed, and the lower mandible is longer than the upper. Their eyes are large but their pupils can be narrowed to a slit, a feature not found in other birds. The large eye is likely an adaptation for crepuscular and nocturnal foraging, and the slit feature may serve to protect the eye from bright light reflected from the water surface during the day. Black Skimmers are strongly sexually dimorphic; males average nearly 30% heavier than females. Juvenile skimmers are brownish with dark streaking above and white streaking below. The bill of a Black Skimmer is an adaptation for foraging on small fish in shallow water. When foraging, skimmers fly low along the water with their bill open and the long lower mandible cutting through the surface. The upper mandible is hinged so that it can snap down and secure any little fish that has made contact with the knifing lower mandible. Skimmers mainly forage early and late in the day and, because they are tactile foragers, may also forage at night. Small fish are the primary prey, but small crustaceans also are taken. The Black Skimmer is polytypic, with three subspecies generally recognized: R. n. niger in North America, and two subspecies in South America. The Black Skimmer is also closely related to two skimmer species found in Asia and Africa. In North America, Black Skimmers breed along the East Coast from Massachusetts to Florida and along the Gulf Coast from Florida to Northern Mexico. In the west, they breed in several colonies in southern California. Skimmers breeding from Massachusetts to Virginia are migratory, and largely spend the winter in Florida. More southerly breeders are often nomadic, either migrating, or remaining more sedentary. For this reason, determining migratory patterns is often confusing. Skimmers outside their year-round range can be found along both coasts of Mexico and parts of Central America. In Massachusetts, Black Skimmers are rare and irregular breeders, although they are regular summer and fall visitors. They may occasionally be abundant in the aftermath of hurricanes. Breeders arrive in late April and typically leave in September and October. Black Skimmers are monogamous and pairs may remain together through the winter and sometimes for several breeding seasons. They are colonial nesters with colonies varying from a few birds to thousands. They almost always breed in colonies with terns. It is thought that they receive protection from the aggressive mobbing behavior that characterizes breeding terns. Most colonies are on islands, beaches, salt marshes, and even rooftops—just about anywhere terns are nesting. The skimmers often form subcolonies and usually nest in the more open, unshaded areas of beaches than terns. At colony sites both sexes are vocal. The most common call is a bark or series of barks that have been likened to the bark of a beagle. Skimmers call during displays, in aggressive situations, and to sound alarm; calls are usually given from within the pair’s territory. Males mate guard females prior to egg-laying. During courtship, they bring fish or twig offerings to the female. Nests are scrapes in the sand made by both males and females, and they sometimes make more than one scrape per territory. The nests are not lined with vegetation. Both parents develop brood patches and share in the incubation of the clutch of four cream colored dark-spotted eggs for the three-and-a-half weeks until hatching. The parents give distraction displays if disturbed. The chicks are semi-precocial at hatching, with their eyes open and bodies covered with down, and they can walk after only a few hours. Both parents brood the young birds. The chicks start to wander from the nest in three to five days but stay within approximately a meter of the nest until fledging. They can fly in about four weeks when they join flocks of adults, but the parents continue to feed them for at least two weeks as the young birds develop their highly specialized foraging behavior characteristic of the species. From the start, the parents feed the chicks whole small fish rather than by regurgitation. Black Skimmer eggs and chicks fall prey to mammals such as rats, foxes, and raccoons. Gulls are the primary nest predators, but oystercatchers, turnstones, and several species of herons also eat skimmer eggs. Falcons and owls take adults. In the past, humans—including market gunners and commercial eggers—killed skimmers for food, and sometimes for the millinery trade. Disturbance that drives adults from their nests can be a threat, too, since chicks die quickly in direct sun. Storms, flooding, and human disturbance can also cause entire colonies to fail. Black Skimmers are listed by various states as Endangered, Threatened, or of Special Concern, with loss of breeding habitat being a major cause. The entire population was considered in decline in the 1960s and 1970s, however most populations have since stabilized and artificial dredge-spoil islands have expanded their breeding habitat. We can only hope that conservation efforts will salvage and protect sufficient breeding habitat for this unique waterbird, to thrive in our coastal waters. William E. Davis, Jr.