The black skimmer is a large coastal waterbird found in North and South America. It is easily recognizable by its striking black and white plumage and its unique bill, which is longer on the bottom than the top. The black skimmer is the only bird with this uneven bill adapted especially for a specialized method of feeding called skimming. The black skimmer uses its bill to skim the water’s surface, snapping up small fish and crustaceans. Its name refers to this distinctive foraging behavior.
The black skimmer belongs to the family Rynchopidae, which contains just 3 species of skimmers worldwide. Besides physical adaptations like its specialized bill, the black skimmer has other interesting traits related to its ecology and behavior. Here we will explore the meaning behind the black skimmer’s name, how its anatomy equips it for skimming, what its taxonomic classification can tell us, and some highlights about its habitat, diet, breeding and conservation status.
What does “black skimmer” mean?
The name “black skimmer” refers first of all to the bird’s plumage coloration. Adult black skimmers have mostly black feathers over the majority of their body, with white feathers on the forehead, nape and underside. The name also describes their unique method of catching prey. Black skimmers fly just above the water surface with their bill open, skimming along as they snap up fish and invertebrates. They are the only bird specialized for feeding in this manner. Their bill has evolved to function perfectly for the skimming technique.
Plumage
Adult black skimmers are primarily black on the back, wings, tail and most of the head. The forehead, nape and underside from chin to tail are white. The bill is black with a bright red and black vertical stripe near the tip of the lower mandible. Legs and feet are red-orange.
Male and female black skimmers have identical plumage. Immature skimmers have a scalier appearance with gray-brown feathers edged in white, a black cap and white forehead, and pale gray bills. Their black and white adult plumage will gradually emerge over the course of several molts as they mature.
The adult’s contrasting black and white plumage functions as disruptive coloration, making the bird harder to see against a background of dark water and bright sky. When floating on the water, the black skimmer’s white underside helps camouflage it against the sky from below.
Bill Shape
The black skimmer’s bill is laterally compressed, knife-like in profile, with a sharp cutting edge. The Mandible halves are of completely different lengths, with the lower mandible 1.5 to 2 times longer than the shorter upper mandible. The lower mandible tapers to a narrowed tip.
This bill is adapted perfectly for the skimming feeding method. When the black skimmer flies along just above the water surface with its bill open, the lower mandible is the first to touch the water. Its knife-edge tip slices smoothly across the surface as the upper mandible trails just above it. Any small fish or invertebrates in the water will hit the lower mandible and be snapped up in the bill. The shorter upper mandible prevents excessive water intake while skimming.
Skimming Behavior
The black skimmer is the only species specialized for skimming as its primary foraging method. Skimming allows it to catch small fish and aquatic invertebrates near the water’s surface.
To skim, the black skimmer flies with its long bill open wide at an optimal depth of 2 to 6 centimeters. Its lower mandible cuts the water while the upper mandible stays above the surface. Touching any prey, the sensitive bill quickly snaps shut.
Skimming black skimmers usually fly just above or into the wind so their airspeed remains slow enough for successful feeding. Their average skimming speed is about 17 kilometers per hour. A skimming black skimmer will swing its bill from side to side to scan a wider swath for potential food.
Taxonomy and Classification
The black skimmer belongs to the family Rynchopidae in the order Charadriiformes. Here is the black skimmer’s full taxonomic classification:
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Charadriiformes
Family: Rynchopidae
Genus: Rynchops
Species: Rynchops niger
Some key points about black skimmer taxonomy:
- The Rynchopidae family contains just 3 extant skimmer species worldwide.
- The genus Rynchops includes black skimmers and one other species, the African skimmer.
- Black skimmers belong to the order Charadriiformes, which includes gulls, terns, plovers and other shorebirds.
- The black skimmer’s closest relatives within Charadriiformes are terns and gulls.
Taxonomically, the black skimmer is the only species within its family and genus adapted for its signature skimming behavior. Its relatedness to other shorebirds hints at its ecology as a coastal species at home near water.
Habitat and Range
The black skimmer inhabits coastal areas across much of North America, Central America, northern South America and the Caribbean islands. Its range extends from southern Canada down to Ecuador and Brazil. Some key features about the black skimmer’s habitat needs and range include:
- Habitats include beaches, sandbars, lagoons, estuaries, salt marshes, and offshore islands.
- Nests on open sandy beaches or exposed flats near shallow water.
- Forages mainly in shallow estuaries, lagoons, ponds or creeks.
- Coastal distribution along Atlantic, Pacific and Gulf coasts of the Americas.
- Northernmost breeding range extends to Nova Scotia.
- Winters along the southern U.S. coast and south to Central and South America.
The black skimmer population in the U.S. is estimated at about 78,000 breeding pairs. Globally, its population is declining but the black skimmer remains widespread and not currently endangered. Loss of nesting habitat is a major threat.
Diet and Feeding
The black skimmer is a carnivorous bird that eats small fish, crustaceans and other aquatic invertebrates. Its unique bill equips it perfectly for catching food by skimming along the water’s surface. Some key facts about the black skimmer’s diet and feeding behavior:
- Feeds almost exclusively by skimming, rarely plunges or dives.
- Main prey includes small fish like Menidia, Fundulus and Anchoa species.
- Also eats shrimp, crabs and other crustaceans.
- May occasionally eat insects and plankton.
- Requires about 128 grams of food daily.
- Often flocks when foraging communally.
- Skims with bill partly open at optimal depth of 2-6 cm.
- Swings bill in arcs to cover broader area.
Thanks to its specialized bill and skimming technique, the black skimmer is a successful predator of small fish and invertebrates in its coastal habitat. It rarely needs to use other feeding methods like diving or plunging into water.
Breeding and Nesting
The black skimmer breeds in large colonies, with nests spaced closely together on open sandy beaches. Key facts about their reproduction include:
- Breeds from April to August depending on latitude.
- Nests on sand beaches, sandbars, gravel pits or rooftops.
- No nest construction; eggs laid in shallow scrape.
- Lay 2 – 5 eggs per clutch.
- Incubation lasts about 21 – 28 days.
- Chicks can fly at 25 – 30 days old.
- Male and female share incubation duties.
- Chicks gather in cr??ches while parents forage.
Both nesting habitat availability and predation heavily impact black skimmer breeding success. Population declines have resulted mainly from loss of beach nesting sites. Common predators of eggs and young include gulls, crows, racoons, coyotes and other animals.
Conservation Status
Although still widespread, black skimmer populations are declining and the species faces a number of conservation threats:
- Globally classified as Least Concern but numbers are decreasing.
- Loss of nesting habitat is a major threat.
- Also threatened by disturbance, predation, pollution.
- Considered endangered in several U.S. states.
- Legally protected under the Migratory Bird Treaty Act.
Key conservation actions needed include protecting breeding colonies, managing water levels at nesting sites, controlling predators, and public education programs. With appropriate habitat management, the black skimmer’s future outlook can remain stable.
Conclusion
The black skimmer is a fascinating bird uniquely adapted for its skimming lifestyle. Its name and bill shape reflect a specific feeding technique that allows it to capitalize on small fish and invertebrates in shallow coastal waters. Although facing some conservation threats, protection of nesting habitat can help ensure the black skimmer continues skimming over American shorelines for years to come. They serve as an indicator for the health of coastal ecosystems on which they depend.
