The sudden flash of yellow in the tree outside the Daly City BART station stopped me in my tracks.

I’d been hustling from the parking lot to catch my 8:30 train -- who knows what going through my head: a meeting, a lunch, a conference call, another meeting. But all that was erased completely by what I soon ascertained was a Townsend’s Warbler hopping from branch to branch in this skeletal bit of parking lot landscaping.

The bird gave me a few seconds to marvel at it, and then blasted off. A speck against the gray sky, and then gone.

Mine wasn’t the only sighting of a Townsend’s Warbler in the last few days. If you follow the communications of the birding community, the little birds are coming through San Francisco in a wave, humbling our morning commutes with their migration from Central America to British Columbia, where they’ll make their nests.

For a birder in San Francisco, this is the time of year when our notoriously celebrated local color and diversity goes to a whole new level.

I’ll be hearing the bright chirp of my favorite Ash-throated Flycatchers any day, and I’ll need to keep an eye out for the annual visit of the brilliant orange Rufous Hummingbirds.

The Pacific Wren is already singing its song in the Presidio, and I know from the photos on Craig Newmark’s Twitter feed that Golden Gate Park is starting to light up with winged migrants.

Spring migration also means it’s time to wish the Golden-crowned Sparrow that has spent the winter outside my bedroom window a safe trip north to breeding grounds in British Columbia and Alaska.

The conservationist in me, when thinking about spring migration, will always tend toward thinking about the challenges these birds face on their long journeys. All too many of these challenges are man-made and avoidable.

Like so many of my colleagues, I’m worried about California’s drought, which depending on who you believe, is either the worst in our lifetime, or the worst in 100 years, or the worst in 500 years.

I worry that the drought will transform our landscape, and break a migratory continuum that stretches all along the Pacific Flyway from South America to Alaska. And I fear that our well-intentioned response to the drought might make things even worse.

San Francisco, however, holds the distinction of not only being a great city to bird, but also being a great bird city. The Golden Gate Audubon Society sponsors an annual Lights Out campaign, encouraging building owners to turn out their lights to avoid confusing migrating birds, and the city in 2011 was the first on the West Coast to approve bird-safe building standards.

But when I see my first Hooded Oriole this spring, I won’t be thinking about all that.

Instead I’ll be thinking about this glorious creature all dressed up in yellow and black, the incredible journey it made to be right here, and how fortunate I am to be part of that by bearing witness to its arrival.

Brigid McCormack is executive director of Audubon California.

(photo by Kevin Cole)