The Fascinating Life of Black Terns
By Luke Matthews
Many people may be familiar with terns as they hold the world record for the longest annual bird migration. The Arctic Tern is the global champion with an astounding pole-to-pole migration of over 40,000 miles annually! These Arctic Terns, along with roughly nine other tern species, frequently visit the coast of California; however, few of them spend much time inland. Of these tern species, the Black Tern is the only one that has significant breeding populations in California’s Central Valley.
Black Terns are a marsh nesting species that has adapted to nesting in rice fields due to a lack of natural marsh habitat in California. In fact, past studies have indicated that over 90 percent of Black Terns in California nest in the rice fields of the Sacramento Valley. These terns nest in loose colonies and build their nests on mounds of dirt in flooded rice fields during the late spring, after rice fields have been planted. As the rice crops grows, it provides important protection from both predators and the hot summer sun. Black Terns are listed as a Bird Species of Special Concern and maintaining planted rice acres in the Sacramento Valley is considered to be a crucial component to ensuring the stability of their breeding populations.
During the breeding season, Black Terns forage on a wide variety of insects, small fish, crustaceans, and amphibians. Once the young have learned to fly, terns will migrate south to spend their winters foraging for fish of the coasts of Mexico, Central America and South America before returning to the Sacramento Valley rice fields to raise another generation.
If you are ever lucky enough to see a nesting colony of Black Terns, you will not forget it. Like most other terns, these birds are extremely protective of their nests and they will fly around squawking at you, as a perceived intruder, and in some cases they will even dive-bomb your head if you get too close!
Luke Matthews is the Wildlife Programs Manager for the California Rice Commission