Black Skimmer

Maximum longevity: 20 years (wild)

Black skimmers were commonly hunted for food before the twentieth century, but are no longer hunted. Their eggs are still valuable to collectors and for food.

Rynchops niger also promotes ecotourism. Breeding colonies attract birders.

Positive Impacts: food ; body parts are source of valuable material; ecotourism

Black skimmers exhibit anti-predator behavior both actively and passively. Individuals form colonies, and this group living helps them passively avoid predation through spacing and numbers. They also employ vigilance behavior as an antipredator mechanism. Individuals of pairs look in opposite directions, or multiple individuals in a colony are able to look in every direction for approaching predators. When threatened by a predator, individuals in a colony will fly and give warning calls that are spread by neighboring individuals until the alarm radiates throughout the colony. Although adults do not exhibit cryptic defense, chicks are cryptically colored and able to blend in to their typical surroundings. Rynchops niger juveniles hide in small scrapes near vegetation where they can blend in to their surroundings.

Black skimmers fall prey to many different types of animals. Mammals and predatory birds often eat adults and juveniles alike. Egg predation is also a problem for them, as even ants, like Solenopsis molesta, Lasius neoniger, and Tetramorium caespitum can be a problem to eggs.

Known Predators:

• red foxes (Vulpes vulpes)
• raccoons (Procyon lotor)
• striped skunks (Mephitis mephitis)
• minks (Neovison vison)
• long-tailed weasels (Mustela frenata)
• gray squirrels (Sciurus carolinensis)
• domestic dogs (Canis lupus familiaris)
• domestic cats (Felis silvestris)
• Norway rats (Rattus norvegicus)
• black-crowned night herons (Nycticorax nycticorax)
• marsh hawks (Circus cyaneus)
• peregrine falcons (Falco peregrinus)
• ruddy turnstones (Arenaria interpres)
• short-eared owls (Asio flammeus)
• great horned owls (Bubo virginianus)
• fish crows (Corvus ossifragus)
• common grackles (Quiscalus quiscula)
• boat-tailed grackles (Quiscalus major)
• red-winged blackbirds (Ageliaus phoeniceus)
• thief ants (Solenopsis molesta)
• mound-building ant (Lasius neoniger)
• pavement ant (Tetramorium caespitum)

Anti-predator Adaptations: cryptic

Black skimmers have distinctive physical characteristics with respect to color and shape. The upper part of the body is black and the lower body and forehead are white. Black skimmers have short tails with white spots on them. They have a bright red-orange bill with a black tip. The lower mandible is longer than the upper mandible by 2 to 3 cm. The feet are bright red-orange and webbed. Rynchops niger juveniles are a mottled brown color and the sexes are indistinguishable from one another. Their upper and lower mandibles are of equal length after hatching but not after fledging.

Black skimmers exhibit sexual dimorphism in that males tend to be larger than females. Males weigh about 365 g while females weigh 265 g. On average, individuals are about 46 cm long and have a wingspan of 112 cm.

Black skimmers are unique in that they have a large pupil with a vertical slit. The eyes are often difficult to see because they are surrounded by feathers.

Range mass: 265 to 365 g.

Range length: 40 to 50 cm.

Average length: 46 cm.

Average wingspan: 112 cm.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: male larger

Black skimmers generally live to between 5 and 15 years of age in the wild, but have a maximum lifespan of 20 years in the wild.

Range lifespan
Status: wild: 20 (high) years.

Typical lifespan
Status: wild: 5 to 15 years.

Rynchops niger is primarily found in bays, estuaries, lagoons, mudflats, beaches, shell banks, spoil islands, and coastal marshes. Individuals nest mostly on sand, salt marsh mats, and dredge spoil. They often choose sites near terns, including Sterna dougallii and Sterna antillarum.

Average elevation: 0 m.

Habitat Regions: temperate ; tropical ; terrestrial ; saltwater or marine ; freshwater

Terrestrial Biomes: desert or dune

Aquatic Biomes: lakes and ponds; rivers and streams; coastal ; brackish water

Wetlands: marsh

Other Habitat Features: riparian ; estuarine

Rynchops niger, or black skimmers, have a large range. They are found in the Nearctic and Neotropical regions. In North America, they can be found on the Atlantic and Pacific coasts of the United States. Black skimmers are seen as far north as New York and in the south along the coast of the Gulf of Mexico. They occurs along the west coast of North America, from California through Mexico. In South America, they occur virtually throughout the continent. They can be found in each coastal and land-locked country. In the Caribbean, R. niger can be seen as far east as the Virgin Islands and Grenada.

Rynchops niger is a migratory species. Individuals from northern North America winter in the southern United States and South America or the Caribbean. Individuals from southern South America may winter farther north, but only as far as Costa Rica. Typically, northern populations of R. niger migrate south in November.

Biogeographic Regions: nearctic (Native ); neotropical (Native )

Black skimmers are piscivores, their diet primarily consists of small fish from 4 to 12 cm in length. Fish that are smaller than 2 cm are fed to young birds. They also eat arthropods, such as crustaceans, and other marine invertebrates.

Fish species eaten include Odonthestes argentinenesis, Brevoortia aurea, Anchoa marinii, Lycengraulis grossidens, Engraulis anchoita, Pomatomus saltatrix, Mugil cephalus, Fundulus heteroclitus, and Anchoa mitchelli.

Black skimmers have a unique foraging behavior in which they fly low over the water while submerging their sharp, elongated lower mandible into the water. Once the prey comes into contact with the lower mandible, the upper mandible closes and the prey is captured. Their method of feeding allows them to be successful nighttime feeders.

Animal Foods: fish; insects; mollusks; aquatic crustaceans; other marine invertebrates

Primary Diet: carnivore (Piscivore )

Black skimmers are important predators in coastal ecosystems in North and South America. They may play an important role in regulating the populations of small fishes. Rynchops niger is also prey for a variety of larger predators.

It has been argued that R. niger exhibits information parasitism by taking advantage of warning signals from nearby colonies of common terns like Sterna dougallii and Sterna antillarum.

Little is known of parasites that affect R. niger. External parasites are rare, but internal parasites have been identified. The flatworms Parvitaenia ibis (Cestoda) and Stephanoprora denticulata (Trematoda) were present in individuals affected by botulism. Rynchops niger young are often victims of diarrheal epidemics that affect 10 to 15 percent of fledglings. The organism responsible has yet to be isolated and identified.

Commensal/Parasitic Species:

• Parvitaenia ibis
• Stephanoprora denticulata

Black skimmers often establish colonies on sandy beaches that could be tourist destinations. Once a colony is established, it is rare for them to leave. For example, black skimmers established a colony in the parking lot at a Dow Chemical Company facility in Texas, making it inaccessible to employees of the company.

Black skimmers are abundant and not in any serious danger of decline. Therefore, the IUCN Red List has the species listed under "Least Concern." Black skimmers are also protected by the US Migratory Bird Act.

Black skimmers were once hunted nearly to extinction for food, but are not threatened by hunting anymore. The coastal habitat of R. niger makes these birds vulnerable to human interference through construction, recreational water activities, fishing, crabbing, clamming, and dredging. In addition, like many birds, black skimmers are susceptible to environmental contaminants. The presence of pesticides can lead to shell thinning in eggs while other pollutants can lead to the formation shell-less eggs. Oil pollution and high levels of metal contamination found in R. niger are concerns as well.

US Migratory Bird Act: protected; no special status

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

IUCN Red List of Threatened Species: least concern

Black skimmers communicate with each other by both vocalization and displays. Their bark has been commonly described as a low-frequency bark like that of a dog. They bark as an anti-predator response, to warn their neighbors of potential danger, and also give a low-frequency bark to display aggression when neighbors intrude on their territory. The barks of males are of a lower frequency than those of females. Typical barking calls have a high frequency of approximately 6 kHz and the longest of these barks can last about 0.5 sec. These barks are often accompanied by head tosses and an aggressive upright posture. A head toss occurs when black skimmers quickly raise and lower the head and bill. In an aggressive upright posture, black skimmers extend their legs, body, and neck and hold the carpals away from the body. They may also open their bill without making noise.

Another aggressive posture is the low oblique. This posture may follow the upright aggressive posture but is less intense. It is often accompanied by head tosses and soft barks. In the low oblique posture they tilt the body down and extend the tail and wings upward. To avoid aggression when moving through a colony black skimmers walk with the bill held upright. When selecting a nesting location, males and females communicate by kicking sand to establish a scrape at that particular spot. This method of communication also allows their neighbors to know where the nest will be made. Black skimmers communicate vocally most often when they are in their own territories.

The tactile senses of black skimmers are important in their foraging behavior. When skimming over the water at night, they use their lower mandibles to make contact with fish and other marine prey before catching them. Their vertical pupils may help their vision during nocturnal feeding or protect their retinas.

Communication Channels: visual ; acoustic

Perception Channels: visual ; tactile ; acoustic ; chemical

Black skimmers begin a courtship process once they arrive at a breeding colony. They form dense flocks and form pairs within about one week. Though individuals may change location in the group more than once, males and females are usually paired within a few days and establish territories. They are monogamous and males aggressively protect their mates. Black skimmers exhibit courtship feeding usually during the evening hours. In this process, a male will present a fish to the female. Once the female accepts the fish and holds it in her beak, the male mounts her and copulation occurs. The female will hold the fish in her beak during copulation and swallow the fish afterward. This is a distinct difference between black skimmers and terns, where females usually eat the fish before copulation. If a male cannot find his mate a fish, he may still be successful in courting her by presenting a stick or a leaf. Copulation may occur several times a day.

Mating System: monogamous

Black skimmers breed annually during the warmer months of summer, generally between the end of April until the beginning of September. Clutch size ranges between 4 and 5 eggs. Egg laying occurs over a span of about 8 days and it is uncommon for female black skimmers to lay multiple eggs on the same day. Incubation takes between 21 to 26 days while the time to fledging usually takes about 28 days. Because males are larger on average, they can take up to 31 days to fledge.

On average, females reach sexual maturity around 3 years of age. The youngest breeding female discovered was 11 months old. Males tend to reach sexual maturity around 4 years of age.

Breeding interval: Black skimmers breed once yearly during the summer months.

Breeding season: Breeding occurs between the end of April and early September.

Range eggs per season: 4 to 5.

Range time to hatching: 21 to 26 days.

Range fledging age: 28 to 31 days.

Average time to independence: 6 weeks.

Range age at sexual or reproductive maturity (female): 11 (low) months.

Average age at sexual or reproductive maturity (female): 36 months.

Average age at sexual or reproductive maturity (male): 48 months.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; oviparous

Both sexes of R. niger attend to the eggs during the period of incubation. Black skimmers protect and care for their chicks until the time of fledging, which can take place 28 to 31 days from hatching. Males tend to feed young chicks more than females, but both sexes feed their young. Rynchops niger chicks are protected from overexposure to the elements by their parents. Black skimmers are territorial and protective of their young and will attack other skimmers, including other fledglings from coming near their nest.

Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female)

The structure of the black skimmer's beak is related to its specialised foraging technique, which is unique to skimmers (2) (4). A feeding black skimmer flies low over water with the beak open and the lower mandible partially submerged, 'skimming' the water. If the lower mandible comes into contact with a prey item, such as a small fish or crustacean, the upper mandible snaps down while the head and neck double back under the body, securing the prey, which may be swallowed in flight or taken back to land (2) (5). The long beak and relatively long neck allow the skimmer to maintain its body position just above the water surface while skimming (2), and the beak can be opened unusually wide so that the upper mandible remains clear of the water. The knifelike edges of the beak help the bird to grasp slippery prey, and the neck muscles are very strong, enabling prey to be pulled from the water as the skimmer flies past (4). Although the black skimmer may sometimes wade, it does not swim or dive (2). Since skimming is a tactile rather than a visual hunting technique, skimmers are able to hunt at night, when many fish species come closer to the surface and strong daytime winds often lessen (2) (5) (7). Skimmers are the only birds in which the pupil of the eye constricts to a narrow vertical slit, an adaptation that may achieve a greater reduction in the pupil than with a circular opening, protecting the eyes from the bright glare of sunlight on water and sand during the day (2) (8) (10). A social bird, the black skimmer roosts and breeds in colonies ranging in size from a few to thousands of pairs, and is often found in the company of gulls and terns, from which it may derive some protection from predators (2) (3) (5) (8). Large, successful colonies usually occupy the same nest site from year to year (5). The species is monogamous, and both the male and female help to prepare the nest and raise the chicks. The nest is a simple, shallow scrape in the sand, into which two to four eggs are laid, hatching after an incubation period of around 21 to 26 days (2) (5). Both the eggs and the chicks are well camouflaged against the sand (2) (8). The black skimmer chick is quite well-developed and able to leave the nest after about a week, with fledging occurring after 28 to 30 days (2). The first attempts at skimming are made within about two days of the first flight, but initial success is low, and the young black skimmer may be dependent on the adults for a further few weeks (5). Interestingly, the two mandibles of the beak are of equal length on hatching. The lower mandible grows continuously faster than the upper, so that by the time the chick fledges it is already nearly 1 centimetre longer (2) (5). Its growth is kept in check by wear against the muddy or sandy bottom in shallow water, or by breakage on hitting obstructions, meaning that beak length and shape is quite variable between individuals and over time (2). The black skimmer is thought to breed from around the age of one to three years, and may live for up to 20 years in the wild (2) (5).

The future of the black skimmer is dependent on the protection of suitable breeding habitat, which is an ongoing problem as human populations expand and are increasingly attracted to beach areas. Larger colonies tend to be more stable, and can be protected by preventing development at breeding sites, restricting access by off-road vehicles, erecting fences and educational signs, and wardening to prevent egg collection and to keep dogs out (5) (8). Annual monitoring of black skimmer populations, which can easily be done from the air to minimise disturbance, has been recommended in order to provide estimates of breeding numbers, and to identify sites needing protection. Monitoring and protection are also needed for fish stocks, to ensure that the quality and quantity are maintained and that any potential effects of pollutants in the food chain identified (5) (8). In South America, it is hoped that the preservation of large stretches of river and adjacent forest to protect local fishing industries will go some way to helping protect the populations of this remarkable bird (2).

The largest of the three skimmer species (4), the black skimmer is an unmistakable bird, best known for its remarkable beak (2) (5). As in all skimmers, this unusual structure is long and deep, with flattened, blade-like mandibles, and the lower mandible is longer than the upper (2) (3) (5) (6). The beak of the black skimmer is bright red at the base and black at the tip, and the upper mandible is slightly downcurved (2) (3) (5). Together with the bright red legs, it provides a colourful contrast to the white underparts and sides of the head, and the black upperparts and cap (3) (5) (6). The eye is somewhat invisible within the black feathering on the head (5), and the body appears unusually front-heavy due to the long beak and large head (2). The wings are long, narrow and pointed (5) (7), and the tail, which is white with a dark central streak, is slightly forked (2) (3) (5). The legs are short, with webbed toes (5) (7). The male black skimmer is significantly larger than the female, with a longer beak, but is similar in colouration (2) (4) (5) (8). Non-breeding adults have a white collar on the neck, and somewhat browner upperparts, while immature birds are browner and more mottled than adults, with a duller beak (2) (3) (5). Three subspecies of black skimmer are recognised. Rynchops niger cinerascens and Rynchops niger intercedens are larger than Rynchops niger niger, and vary in the colour and markings on the wing linings and tail (2) (5) (6). The black skimmer has a relaxed and buoyant flight (2) (3) (5), and calls with an unusual, dog-like nasal “yip” (3) (5) (7).

R. n. niger feeds mainly in coastal waters that are protected from open surf, such as in estuaries, bays, tidal pools, inlets and creeks. Nesting occurs on sandy beaches, sandbars, islands, shell banks, dredge islands and salt marsh, and the species may also occasionally be found on inland lakes (2) (5) (8). The two southern subspecies nest mainly along sandbars and beaches of inland rivers, at times when water levels are lowest, and also use coastal beaches, lagoons, islands and estuaries (2) (3) (5). The black skimmer has been recorded at elevations of up to 3,800 metres on the shore of Lake Titicaca in Bolivia (2).

The black skimmer occurs throughout the Americas, from the United States, through Mexico and Central America, and south into much of South America (9). R. n. niger is the most northerly subspecies, found along the Atlantic and Gulf coasts of the United States, south through Mexico and into Panama. A western population also breeds from southern California to Mexico (2) (5). R. n. cinerascens is found in northern South America and R. n. intercedens in southern South America (2) (3) (5). The species is migratory, with northern populations moving southwards during the winter, and southern populations sometimes wintering on the coast or moving to Central America or the Caribbean (2) (5) (8).

Classified as Least Concern (LC) on the IUCN Red List (1).

During the 19th Century, the black skimmer population was greatly reduced due to intense egg collection and hunting for feathers and food (2) (5) (8). Although the species occurs over a large geographical range and currently has a relatively large global population (9), it still faces a number of threats. In the United States, human disturbance at breeding sites is a major cause of colony failure, with sandy beaches increasingly being used for recreation and commercial development, or suffering disturbance from people, dogs and off-road vehicles (2) (5) (8). Even slight disturbances can affect nesting success (8), reducing hatching and fledging and even causing adults to abandon the colony (5) (11). Despite being protected by law, the eggs are sometimes still taken, and in some areas the deliberate destruction of eggs and chicks and the shooting of adults is a problem (2) (5). Predators associated with humans, particularly dogs, cats and rats, may damage some colonies, and chemical pollution is also of concern, with organochlorines and heavy metals thought to accumulate in the eggs and feathers when the black skimmer feeds on contaminated fish (2). In South America, the rivers along which the black skimmer breeds are often the focus of human settlement, and increasing use of beach habitat by humans, as well as the collection of eggs and the possible depletion of fish stocks, poses a threat to many colonies (2) (3). The black skimmer is quite adaptable in its use of feeding and nesting sites, often using man-made ponds and ditches, and breeding on gravel roofs and on areas of dredge deposition from oil exploration. However, the use of these artificial habitats results to a large extent from the black skimmer being displaced from natural beaches. Although adapted to endure natural disasters and heavy predation by readily changing colony site and re-nesting, the species is dependent on areas of open, calm water with a high concentration of fish, and so is vulnerable to any threats to fish populations, such as from oil spills or chemical pollution (2).

A medium-sized (16-20 inches) gull-like bird, the Black Skimmer in summer is most easily identified by its black upperparts, white underparts, and bizarre black and orange bill. In winter, the Black Skimmer becomes slightly grayer on the head and body. Male and female Black Skimmers are similar to one another in all seasons. The Black Skimmer breeds along the Atlantic coast of the United States south of Massachusetts, on the Gulf coast from Florida to northeastern Mexico, and along the coast of southern California south to central Mexico. In winter, this species withdraws from the U.S. Atlantic coast north of North Carolina, and may be found from there south on both coasts to Central America. Other subspecies occur along coasts and on large rivers in South America. Black Skimmers in North America breed on sandy beaches and barrier islands in colonies near those of other seabird species, utilizing similar habitat types during the winter. In South America, inland populations also exist which inhabit sandy river banks. Black Skimmers eat a variety of small fish and crustaceans. In appropriate habitat, Black Skimmers may be observed flying low over calm water. They feed by lowering the bottom half of their bill (which is much longer than the top half) into the water as they fly, quickly closing their bill when the submerged half of the bill touches a small fish. Black Skimmers are primarily active during the day.

Threat Status: Least Concern

A medium-sized (16-20 inches) gull-like bird, the Black Skimmer in summer is most easily identified by its black upperparts, white underparts, and bizarre black and orange bill. In winter, the Black Skimmer becomes slightly grayer on the head and body. Male and female Black Skimmers are similar to one another in all seasons. The Black Skimmer breeds along the Atlantic coast of the United States south of Massachusetts, on the Gulf coast from Florida to northeastern Mexico, and along the coast of southern California south to central Mexico. In winter, this species withdraws from the U.S. Atlantic coast north of North Carolina, and may be found from there south on both coasts to Central America. Other subspecies occur along coasts and on large rivers in South America. Black Skimmers in North America breed on sandy beaches and barrier islands in colonies near those of other seabird species, utilizing similar habitat types during the winter. In South America, inland populations also exist which inhabit sandy river banks. Black Skimmers eat a variety of small fish and crustaceans. In appropriate habitat, Black Skimmers may be observed flying low over calm water. They feed by lowering the bottom half of their bill (which is much longer than the top half) into the water as they fly, quickly closing their bill when the submerged half of the bill touches a small fish. Black Skimmers are primarily active during the day.

The black skimmer (Rynchops niger) is a tern-like seabird, one of three similar bird species in the skimmer genus Rynchops in the gull family Laridae. It breeds in North and South America. Northern populations winter in the warmer waters of the Caribbean and the tropical and subtropical Pacific coasts, but the South American races make only shorter movements in response to annual floods which extend their feeding areas in the river shallows.

Caribbean; North America; northern Cape Cod to Gulf of Mexico

coastal regions (and inland)