Birds that migrate from Brazil to Seattle each summer face new threat
July 28, 2024 at 6:00 am Updated July 28, 2024 at 6:00 am
Cindy Barrett, right, and Abby Carter, 11, on a tour with Ballard Kayak & Paddleboard, check out purple martins seen in a nesting colony made up of natural gourds hanging from derelict wooden pilings on Shilshole Bay in Seattle on June 29. “These kayaks allow us to get into some places to see really unique wildlife... (Karen Ducey / The Seattle Times)More
By
Kate Perez
Seattle Times staff reporter
On the far west side of Ballard in Shilshole Bay — an area typically only accessible by boat, canoe or kayak — dozens of dark purple and blue birds swoop through a forest of decaying wooden poles. Others dive in and out of human-made bird houses from natural gourds that hang from the poles20 feet from the water’s surface.
These are the homes of the purple martin, a bird locals are fighting to protect as nesting areas on the Seattle waterfront become increasingly scarce.
The purple martin, North America’s largest swallow, has migrated to the West Coast from southeast Brazil for generations, arriving in the spring and typically leaving by the end of August. The state doesn’t keep an official tally of the bird’s population, but experts say at least 300 flock to Western Washington each year.The birds are attracted to the West Coast because of its long and warm summer days that allow them to hunt for food for longer periods of time.
A purple martin hangs out on a gourd in its nesting colony in Shilshole Bay in Seattle on July 18. Purple martins are a bird species that are not endangered, but their homes are being taken down throughout the Seattle area. (Karen Ducey / The Seattle Times)
They prefer to make their homes near water in dead trees and logs known as natural snags, or in cavities like woodpecker holes and other crevices in docks and the posts that support them, called pilings. These natural habitats have become harder and harder to come by, though: More and more of these docks and pilings are being removed by state, county and city agencies around the Seattle area, including at Elliott Bay.
Like the poles in Shilshole Bay, some of the pilings are encrusted with barnacles and seaweed. Many have been treated with toxic chemicals to preserve the wood against water decay. When they’re removed, so are the homes of these birds.
Now, a small group of local researchers is racing to protect and relocate the remaining habitat before more pilings are removed in August.
Thousands of purple martins “nested in natural snags and cavities, but then they started declining … as snags became scarcer and scarcer,” said Kimberle Stark, a King County Senior Water Quality Planner.
Natural snags started to disappear from Washington’s coast and near other U.S. waterways as natural forest and coastlines became commercialized and industrialized.
“There’s no natural snags anymore, so [the birds are] completely dependent on people putting up artificial houses,” Stark said.
A purple martin peeks out of a nesting box at another approaching bird at their colony on Shilshole Bay in June. (Karen Ducey / The Seattle Times)
Legacy carried on
Though they are not listed as an endangered species, the purple martin population is low in Washington and considered a Species of Greatest Conservation Need by the Washington Department of Fish and Wildlife, which means human intervention is necessary for the birds’ success.
A loss of habitat has long threatened purple martins’ ability to reproduce. So has a decrease in insects to hunt and eat due to an increase in pesticide use. The state population dropped so much throughout the late 1980s and early 1990s that a local environmental scientist named Kevin Li started building homes for the birds as a passion project in 1996.
Li is responsible for many of the gourds hanging throughout King County, homes that simulate the natural nesting cavity these birds prefer. After Li started stringing up gourds in Western Washington, the number of birds jumped from an estimated one nesting pair in Shilshole Bay in 1996 to about 32 nesting pairs along the Seattle shoreline, plus 74 more on Vashon Island in 2004. After Li died in 2006, his friends continued his mission.
Jean Power, King County Environmental Lab field science unit supervisor, has been involved with the purple martin habitat restoration efforts since before Li died. Power inherited the project after his death, she said, and now works with Stark and her husband, Carl Bevison, on the project.
“[The birds] suck you in,” Stark said. “Kevin was so passionate about them … You do become kind of obsessive about them.”
A purple martin nesting colony is seen on gourds and boxes on derelict pilings in Shilshole Bay in Seattle on July 18. Purple Martins are a bird species that are not endangered, but their homes are being... (Karen Ducey / The Seattle Times)More
With their high-pitched, flutelike chirps and dark blue wings, watching the purple martin can be captivating. When they fly, their wings look like silver stars. They often swoop and divebomb each other, squabbling before they return to their respective gourds.
Power and the others maintain many of the gourds. Bevis said he and Power climb on ladders each year in fall or winter and take down every gourd to clean and perform maintenance before the birds migrate back in May. The group also purchases new gourds yearly.
The total number of bird pairs is unknown, since there’s no concerted effort to track them across the state. But Stark estimates about 150 pairs migrate to the sites she and her colleagues maintain, including at spots in the lower Duwamish River, Shilshole Bay and Terminal 91 in Elliott Bay. Stark said this lack of tracking makes it difficult to know how many birds need homes. It also makes it tricky to get support from state agencies.
“It’s kind of unfortunate. They’re a vulnerable species,” Stark said. “There’s no monitoring, there’s no coordination.”
Kayakers paddle past a purple martin nesting colony made up of natural gourds hung from derelict wooden pilings on Shilshole Bay while on a tour of the Ballard Locks in Seattle in June. (Karen Ducey / The Seattle Times)
The biggest issue facing purple martins is a lack of natural habitat, Stark said. Purple martins prefer nesting in colonies in wide, open spaces where they can fly freely and catch insects to eat.
But docks and pilings across King County are increasingly being extracted, since many of these structures have been treated with creosote, a chemical used to preserve wood. The product is tough to break down and, according to the Centers for Disease Control and Prevention, can remain as a tar-like mass in the water. It can also move into the soil and then to groundwater, resulting in dangerous creosote buildup in plants and animals.
Pilings have already been removed along Elliott Bay, and they will have to move gourds from Myrtle Edwards Park before extractions begin on Aug. 1, Stark said. When these pilings are removed from the area by government agencies, Stark and her team try to find nearby locations to relocate the gourds so the birds can find their homes from the previous year.
The Port of Seattle is actively partnering with Stark, her colleagues and other groups to relocate the gourds for purple martins to use in future seasons. Jenn Stebbings, Port of Seattle Habitat Restoration and Stewardship program manager, said the Port has worked with the group to relocate gourds at Terminal 91 close to their original locations.
The gourds now reside on tall, metal poles that are environmentally friendly.
The Port of Seattle has had to consider the trade-offs of removing pilings. |
