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Mothers of the Marsh: California Least Terns
By Whitney Thompson
The endangered California Least Tern (Sternula antillarum) is one of Bolsa Chica's migratory marsh mothers. As a migratory species, the California Least Tern flies to Central and South America during the fall and winter months before flying north to breed in warmer climates in the spring and summer. Bolsa Chica is one such nesting location along the California coast that offers a clear nesting area free of regular human foot traffic and reduced predator interference.
California Least Terns are parents that have instilled the proverb, “it takes a village to raise a child,” to heart. These birds are communal nesters where mothers and fathers alike work together to protect the colony and its chicks. The mother chooses the small scrape (divot) in the sand, where 1-3 eggs will be laid. (Both the mother and the father make scrapes in the sand as potential nests near other terns, but it is the mother that ultimately decides which will be the nest for her eggs.) The eggs are a light brown to olive color with a myriad of speckles closely resembling the sand that they are laid in. This camouflage serves as further protection from predators.
The eggs, once laid, are incubated by both parents, but observations show that the mother spends more time on the eggs at the start of the incubation period. Incubation of the eggs goes on for 19-25 days, wherein the parents will both incubate and defend the eggs through mobbing behaviors with the colony. Occasionally the eggs are left unattended, but it never for very long.
Once the eggs hatch, both parents typically tend to their children for two to three months before the children are fully independent. They bring food for the newly-hatched chicks, and the chicks stay in the area of the original nest, finding places to hide while the parents are hunting (Bolsa Chica nest sites have arched tiles placed throughout the nest sites for this purpose).
After about three weeks, the chicks have fledged and gained their first flight feathers. Once the chick can fly, they may stay with their parents for two to three months before becoming fully independent.
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