A tiger swallowtail butterfly visits a planting of Guem, which flowers through the summer. (Mike Benbow / Herald file)

A tiger swallowtail butterfly visits a planting of Guem, which flowers through the summer. (Mike Benbow / Herald file)

Yellow butterflies blossom throughout Evergreen state

Scientists believe warm weather and flower gardens are helping tiger swallowtails thrive.

EVERETT — An abundance of yellow butterflies has made it a colorful summer in the Pacific Northwest.

It’s not just casual gardeners who have noticed the boom in tiger swallowtails. Across the Evergreen state, on either side of the Cascade Curtain, scientists have been struck by the increase in these striking specimens.

“It’s not every place in the U.S. or in the world that gets to see these large, beautiful butterflies,” said David G. James, an associate professor and butterfly expert with Washington State University in Prosser. “You’re very lucky to see these butterflies here.”

The boom might have something to do with a series of warm springs and summers, along with fewer birds and wasps hunting them down.

Tiger swallowtails are native to Washington, and not uncommon.

They’re the largest butterfly in the western United States, James said. Wingspans can reach 5 inches.

People often mistake them for monarchs, the iconic migrating butterflies. The confusion is something of a pet peeve for experts.

Monarchs are orange and black — never yellow. They do resemble tiger swallowtails in size and in how they fly.

“The monarch gets a lot of publicity, and for good reasons,” said Richard Zack, a WSU entomologist in Pullman. “It’s a migrating species and it’s not all that common in the Pacific Northwest. Sometimes that maybe takes away from our appreciation of this really beautiful butterfly that we do see a lot more, which are the swallowtails.”

You might see a monarch in Western Washington, Zack said, but only rarely.

Several types of swallowtails live in Washington. In Snohomish County, it’s the western tiger swallowtail.

They don’t travel far. Tiger swallowtails typically live their lives within a five-mile radius, James said. Their ability to feed on a variety of plants allows them to adapt well to suburban settings.

“Most of the populations you would be seeing would be from people’s gardens and from parkland,” he said.

A movement to promote pollinator-friendly gardens has likely helped boost local butterflies and bees. The Snohomish Conservation District hopes to encourage more.

“When we do all of our projects, we try to make sure we have enough flowering plants mixed in,” said Ryan Williams, program manager with the conservation district. “We’ve been starting to work with some landowners and community gardens to get more native pollinators. We’re working with them to help put in native plants that have the right mix of flowers, that will flower throughout the year to create the oases that they need.”

Tiger swallowtails are hardy critters, with some interesting survival tricks.

“They’re called swallowtails because they have these tails on the hind wings,” James said. “They actually do have a function. They divert attacks from predators. Their main predators are birds. The birds go for the tails.”

Instead of biting off a butterfly’s head, they’ll take a chunk of tail.

“A lot of people think butterflies are very weak,” James said. “That’s not true, as demonstrated by the tiger swallowtail. They can lose their tail, in some cases most of their hind wing, and still fly quite well.”

That describes one of approximately 150 butterfly species in Washington. About 20 of them live west of the Cascade Range. Some aren’t doing as well as the tiger swallowtail, though. Several are endangered or candidates to be considered endangered.

The season’s about over for the tiger swallowtail.

“We see them pretty consistently from mid spring through about this time,” Zack said. “From there, I think we’re going to see fewer and fewer of them. That’s normal biology.”

They lay eggs that will hatch into caterpillars in the fall. They’ll spend the winter as a pupa, or chrysalis, camouflaged on tree branches. A new batch of butterflies will emerge next year.

As tiger swallowtails disappear for the year, look for other species to enter the picture.

“You have to follow the flowers,” said Melanie Weiss from the Washington Butterfly Association.

Weiss is no butterfly scientist. She has a background in education, teaching children with learning disabilities to read and write. She caught the butterfly bug about eight years ago.

Now, she tallies them in her Bellevue backyard and heads to the mountains with like-minded enthusiasts.

She’s recently started seeing woodland skippers in her yard. As she heads further afield, she expects to come across Milbert’s tortoiseshells or red admirals, maybe even a smattering of echo azures.

“These butterflies wax and wane,” Weiss said. “Some years I see them and some years I don’t.”

Noah Haglund: 425-339-3465; nhaglund@herald net.com. Twitter: @NWhaglund.

Want to learn more about local butterflies and the people who study them? Check out the Washington Butterfly Association at www.wabutterflyassoc.org.

The Xerces Society (www.xerces.org) offers a wealth of gardening tips to promote butterflies and bees. The Portland-based group has compiled a list of conservation guidelines and pollinator-friendly plants that do well in this region: www.xerces.org/pollinators-pacific-northwest-region.

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