Southern California is located along the Pacific Flyway, a migratory route for birds that extends from Alaska to Patagonia — and one that provides an unparalleled birding experience twice a year in the fall and the spring.
Right now, San Diego County residents have a prime vantage point to see the action as spring migratory birds arrive from March through May. Some will stop to rest and refuel before continuing to northern breeding grounds, while others will breed here and stay until the end of the summer.
Compared to the fall migration, which is more gradual, the spring migration is on a shorter timeline and features a higher number of birds, so it can feel more intense, said Kevin Burns, curator of birds for San Diego State University’s Museum of Biodiversity and a professor in the department of biology. The birds are also more colorful after molting their drab winter feathers in exchange for brighter “fancy clothes” that help them attract a mate, Burns added.
“It can be a little bit more exciting than the fall migration — kind of like the Super Bowl of birding,” he said with a laugh.
These 7 species of migratory birds are among the millions of birds that will come to San Diego County this spring. More information on individual bird species can be found through the Cornell University Lab of Ornithology bird guide, and timely updates on local migratory bird populations will be at BirdCast.info starting on March 1.
The San Diego Audubon is also encouraging residents to participate in its “Lights Out, San Diego!” campaign from March 1 to June 15, through which residents can pledge to turn off non-essential lighting in the evening. More than 80 percent of North America’s migratory birds travel at night and are highly susceptible to light pollution, according to the organization, which can cause them to be disoriented or collide with buildings, as well as delay migration, among other concerns.
California least tern
Head to Mission Bay for a chance to see the California least tern, the world’s second smallest tern at about 9 inches long. The endangered coastal bird builds its nest on sandy beaches, coastal strand and salt flats, which can make it vulnerable to predators such as red foxes, American kestrels and owls, plus domestic cats and raccoons when it nests in more urban areas.
“Most everything is a threat,” said Lesley Handa, the lead ornithologist at the San Diego Audubon.
Before the bird arrives in San Diego in March and April to breed, the San Diego Audubon holds restoration events at the birds’ nesting sites around Mission Bay to get ready for them, pulling weeds and taking care of the native plants. Despite ongoing federal and statewide monitoring of its population numbers, Handa said there is still a lot to learn about the California least tern, including its migration. The birds will stay in the county until about mid-September.
Elegant tern
Those seeking more tern time can look for the elegant tern, a medium-sized bird that arrives in the county in late March and April from its winter home along the South American coast. Flocks show up to breed near the San Diego River, coastal areas like the Batiquitos Lagoon in Carlsbad as well as at the South Bay Salt Works, according to Handa.
Located within the San Diego Bay National Wildlife Refuge, the Salt Works temporarily closes during the terns’ nesting season. Handa said that San Diegans cycling in the South Bay (such as along the 24-mile Bayshore Bikeway) can peer over into the Salt Works during the breeding season for a chance to potentially see thousands of terns at a time.
Hooded oriole
The hooded oriole is a common bird in San Diego during springtime. Traveling from Mexico, where they spend the winter, hooded orioles arrive in San Diego in March to breed and stay through the summer. These are brightly colored birds — the males have a vibrant yellow-orange body and black wings, while the females are a paler yellow — so they can be easy to spot.
Making themselves at home, hooded orioles will use hummingbird feeders and make woven nests out of plants, such as large birds of paradise and banana trees, Burns said, both of which grow well in San Diego.
“They’re just really beautiful and people connect with them a lot because they can be a backyard bird,” he added.
Least bell’s vireo
The least bell’s vireo arrives in San Diego from its winter home in Baja California in mid-March to early April to breed. The bird can be seen in riparian areas, which are the transition zones between land and waterways such as rivers and streams. In San Diego, this includes along Chollas Creek, in the Tijuana River Valley Regional Park or at the butterfly garden at San Dieguito County Park, Handa said, though birders may be more likely to hear the bird than see it; the males have up to 15 different varieties of song.
The least bell’s vireo has been listed on U.S. Fish and Wildlife Service’s endangered species list since 1986, in part due to the loss of its riparian habitat from human development. But the bird also has to contend with the brown-headed cowbird, which is known to lay its eggs in other bird’s nests, including the least bell’s vireo’s. The unsuspecting vireo will then raise the cowbird chicks, which grow faster than its own and outcompete the vireo nestlings for food. As Burns explained, “There’s so much drama in the bird world.”
Northern rough-winged swallow
Journeying from its winter grounds in Mexico and Central America, the northern rough-winged swallow started arriving in San Diego in February, Handa said, and is one of Southern California’s earliest spring migratory birds. It will breed here and stay through the summer and can be spotted in riparian areas — much like the least bell’s vireo — including Chollas Creek, the Tijuana River Valley Regional Park and the Sweetwater River.
According to Handa, one way to spot the northern rough-winged swallow is to look up; the swallows will be seen flying over the water and catching insects midair, whereas other migratory birds in riparian areas, such as the yellow warbler and yellow-breasted chat, may more likely be seen hopping around in vegetation.
Swainson’s hawk
With one of the longest migrations of any American raptor, Swainson’s hawks travel in the spring from their wintering grounds in Argentina to breed in North America, with some reaching as far north as Alaska. Along the thousands-of-miles journey, they’ll stop in San Diego County’s Borrego Valley — part of the Anza-Borrego Desert — from March to late April, sometimes earlier, for a bite to eat.
“If we have abundant rains and we have lots of flowers, that’s going to attract caterpillars and other insects,” Burns said.
After heavy rains in San Diego County this winter, there’s a good chance the birds will show up in high numbers to feed on the bugs. Swainson’s hawks often travel in groups of tens of thousands of birds, sometimes with a mix of other species, according to the Cornell University Lab of Ornithology.
Burns said birders could spot over 100 hawks in the Anza-Borrego Desert each day. Last year, about 16,000 Swainson’s hawks were recorded in the area during the spring migration season, according to a census conducted by Borrego Valley Hawkwatch, part of the Anza-Borrego Desert Natural History Association. San Diegans interested in participating in the Hawkwatch count, which is conducted each year from Feb. 21 into April, can learn more at the organization’s website.
Wilson’s warbler
Another common spring migrator in San Diego is the Wilson’s warbler, a songbird that es through San Diego County on its route from Mexico and Central America to its northern breeding grounds. The bird es through every state in the lower 48 on its upward journey, so birders across the country can keep an eye out for these bright yellow birds.
In San Diego, the Wilson’s warbler will show up around mid-March and can be spotted at locations such as Famosa Slough near Mission Bay but will also venture into more urban areas, Handa said. Like many migratory birds ing through San Diego County, Handa notes that there can be a short window of time to spot Wilson’s warblers.
“Migration is kind of tricky, because if you’re not out there looking for the migrants, you might not see them,” Handa said. “You have to be there at the right place at the right time.”
