As if a remarkable migratory superhighway hosting more than a billion birds wasn’t enough of a natural spectacle, bird enthusiasts up and down the West Coast have been raving about rarities. There was the first-ever sighting of a Redwing inAlaska, and a Falcated Duck in California. And then there were all those Snowy Owls pouring into the Pacific Northwest.

Maps of the Pacific Flyway tend to involve long curving arrows stretching from Alaska all the way, in some instances, to Patagonia. And these illustrations suggest a closed ecological system where birds take to the air and move en masse with a precision akin to the movement of the planets. But the rare birds are proof that accidents do happen.

There is no one explanation for how birds get so far off course. Researchers believe that, in some instances, the internal guidance systems that keep birds on course get out of whack – like a broken GPS system – and the birds head in the wrong direction. This is thought to happen more often in less mature birds. Other times, the birds can get transported away in a strong storm.

“A flyway is a living, breathing thing, and as such there is an element of randomness involved,” said Nils Warnock, executive director of Audubon Alaska. “If there’s anything we’ve learned from nature is that we should expect the unexpected.”

Warnock was among the first to visit the Redwing in a Seward, Alaska, yard in November. He also went out in December with fellow staffers and later his family to see a Dusky Thrush in an Anchorage neighborhood. Both birds were visitors from Asia that, by all rights, shouldn’t have been here.

Here is video of a Dusky Thrush shot closer to its home, in China:

California gets a lot of rarities, and this year has been no different. There was the Red-flanked Bluetail, thousands of miles from home, hopping around a remote island off Southern California. And then there was the Falcated Duck that wintered in a refuge in Colusa County, drawing thousands of birders from around the state.

“It was pretty fascinating to see this duck mixing with all the other ducks in some of the restored wetlands here in California’s Central Valley,” said Dan Taylor, executive director of Audubon California. “It goes to show that if you create a welcoming environment, you never know what’s going to show up.”

Washington saw a wide range of rare species that inspired extreme birding, from the individual Ross’s Gull that visited Palme rLake in the depths of theOkanoganNational Forestto the Ross’s Goose co-mingling with a large flock of Snow Geese in the Skagit this spring.

The Snowy Owl situation was something altogether different from the rare bird sightings mentioned above. Every few winters, for reasons only partly understood, Snowy Owls come pouring out of Canada into the Lower 48 in events called irruptions. What was remarkable about this irruption was the sheer number of birds sighted in theUnited States.

“It was a notable situation throughout Washington and the Pacific Northwest,” said Gail Gatton, director of the Seward Park Environmental & Audubon Center in Seattle, Washington. “We received inquiries from people as far away as Texas, seeking information on where best to see the owls if they made an excursion here for that purpose.”

The use of the Snowy Owl as a main character in the Harry Potter books has increased awareness about the owls with a very broad audience. But when you see one in real life, you quickly forget the association with the books or the movies. It’s an awesome sight to watch it dive from its perch atop a snag to hone in on a vole.

The Snowy Owls are just further proof that perhaps one of the best things about the Pacific Flyway is the surprises.