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12.13: Rynchops niger: Black Skimmer

Difficulty Level: At Grade Created by: CK-12
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Common Name

  • Black Skimmer


The black skimmer is a common bird found mostly on coasts. These birds are medium sized. They range from 15-20 inches and weigh about 15 oz. They are commonly known for their big red bill and red-orange legs that have webbed feet. Their top bill is longer than the bottom bill so that they skim along water to catch food, hence its name black skimmer.

The complete taxonomic classification is:

  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Aves
  • Order: Charadriiformes
  • Family: Rynchopidge
  • Genus: Rynchops
  • Species: R. niger


Black skimmers have a wide range of places they live. They are commonly found on the east and west coasts of South America and southern North America. Since they live on the coast, they make a home on sandy shores, shallow bays, or at public beaches.


Cell Biology

The black skimmer has many eukaryotic cells. Just like every other eukaryotic cell, they have many organelles inside. One of these organelles is the mitochondria, which is the ¨power plant¨ of the cell where sugar is burned for energy. There are other very important organelles such as the vacuoles, which act as a storage center, the nucleus that contains genetic information about how to build thousands of proteins, and the ribosomes, which are non-membrane bound organelles that produce proteins.

Some cells need to grow and divide. This process is called cell division, and this happens when a cell is repairing tissue, embryos are growing, and for any growth. Mitosis is when the nucleus divides, and each new cell contains a copy of the DNA of the original cell. Meiosis is a form of cell division in which the cell divides to produce gametes with one half of the chromosomes of the parent cell. Chromosomes contain the cell’s DNA.


The black skimmer is a bird that evolved from bipedal dinosaurs, theropods. Theropods are similar to Deinonychus, which was discovered in the 1960s and was a very important discovery. Deinonychus is an extinct dinosaur that was a predatory carnivore. It lived in North America 110 million years ago, and had bird-like features. These bird-like features consisted of having feathers, wings, and clawed feet.

Scientist are still not sure how wings and flight evolved, but they do have some hypotheses. Some believe that wings were modified arms to help animals jump higher. Others think that it came from ancestors who lived in trees.


Black skimmers prey on shrimp and small crustaceans. They have a wide variety of predators. Here is a list of their known predators:

  • black-crowned night herons
  • boat-tailed grackles
  • common grackles
  • fish crow
  • red-winged blackbirds
  • thief ants
  • mound building ants
  • pavement ants
  • great horned owls
  • short eared owls
  • ruddy turnstones
  • peregrine falcons
  • marsh hawks
  • Norway rats
  • domestic cats
  • domestic dogs
  • gray squirrel
  • minks
  • long-tailed weasels
  • striped skunks
  • raccoons
  • red foxes

These birds’ egg-laying process lasts about eight days. Their clutch size is about four to five eggs. They are able to mate when 48 months (male) and 36 months (female) old. Black skimmers usually mate during the end of April until early September.

Anatomy and Physiology

This bird has a four-chambered heart that delivers oxygen for a high metabolism. They also have two respiratory cycles, unlike mammals, who have one. The first cycle is to inhale air in posterior air sacs, then exhale from posterior sacs. The second cycle is when the air is inhaled from the lungs to anterior air sacs, then exhaled from anterior air sacs. These cycles happen at the same time and help remove extra body heat during flight. The black skimmer has three parts in their digestive system: the crop, gizzard, proventriculus. The crop is a food storage for later processing or feeding nestlings. The gizzard is a posterior muscular stomach. Its basic task is to grind food. The proventriculus is an anterior glandular stomach that makes gastric acid and digestive enzymes. Most birds, including the black skimmer, lack in having a good sense of smell, but their vision and hearing are good. The black skimmer is also the only bird whose pupil has a narrow vertical slit that protects eyes from sun, sand, and water during the day.


The black skimmer hunts for their food at night by skimming along the water until they catch something. One of their interesting characteristics is that they never dive or swim in water because they can’t. These birds are very social and associate with other black skimmers during the day. Most of the time these birds try to stay in group living so they can avoid predation. Both sexes attend to their eggs during the incubation period. The black skimmers are also monogamous, and the male protects his mates.




  • Alaysja Clark

Supervising Faculty

  • Amy Huff Shah


  • Museum School, San Diego, California


  • Published prior to review.

Edit History

  • Created: April 5, 2013
  • Version 1.0 submitted to CK-12: July 4, 2013
  • CK-12 edits: in progress


  • Middle School (grades 6-8)

Opening image copyright by tea maeklong, 2013. Used under license from Shutterstock.com.

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Date Created:
Jul 18, 2013
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