We're in the middle of winter, which means it's the best time of year to see a variety of migrating birds. And if you head to Bedwell Bayfront Park, you're bound to see bird watchers equipped with scopes and binoculars admiring a yellow-rumped warbler or an American avocet.

Many of these birders use eBird, a joint program by the Cornell Lab of Ornithology and the Audubon Society that allows birders anywhere in the world to report sightings through an app. Local bird watchers reported 143 unique species in Bedwell Bayfront Park from the months of December to February over the past decade, on average over double the amount of bird sightings over the rest of the year.

According to Andrew Farnsworth, a researcher with the Cornell Lab of Ornithology, the start of the cold season marks a time when many species fly down from the northern regions to the south in search of warmer climates. When spring rolls around, they'll return to their original territories to breed.

"Some of the early ones start coming in August," said Chris MacIntosh, an avid birder and founding member of Friends of Bedwell Bayfront Park who also serves on the board of directors of the Sequoia Audubon Society. "And then it builds up to a crescendo around December and January – starting in February or March, they'll start disappearing again."

Some species are also more noticeable due to behavioral changes in the cold months, said Farnsworth, who gave as an example waterfowl forming groups.

To introduce locals to the wide variety of wintering birds, Friends of Bedwell Bayfront Park and the Sequoia Audubon Society are leading a series of free guided bird walks on the first Saturday of every month through March. Beginners are welcome, and the guides always bring extra binoculars to share with attendees.

"We have the wonderful treasure of wintering waterfowl," said MacIntosh, who leads some of the walks. "You can see birds pretty close up here. If you go out in July, there are not as many birds."

The walks informally started around 2008, when members of Friends of Bedwell Bayfront Park would set up scopes and invite passersby to get a close-up look at the birds, said MacIntosh. In the winter of 2017 to 2018, the organization partnered with the Sequoia Audubon Society to offer more structured tours.

On a sunny and slightly breezy morning this month, The Almanac and about 15 attendees saw 29 unique species over two hours on one of these guided walks. Year-round residents including Canada geese honked as they glided overhead, and the bright colors of Anna's hummingbirds' plumage wooshed by.

"The primary equipment is eyes and ears," said MacIntosh. "It's noticing. It's starting to observe. It's listening and hearing any birds. If you want to get into [bird watching more, a pair of binoculars is helpful."

Along the trail lining the paved road through the park, the group paused to admire a paddling of ducks floating on an inlet of the Bay at high tide, exhibiting the seasonal behavior that Farnsworth described. The canvasbacks were easily identifiable with their red-brown heads and white backs. The bright emerald glint along the male green-winged teal shone through a large scope.

We stood watching for about a half-hour. A group of white-crowned sparrows came out of hiding from a fennel brush.

Bay Area native Christin New, who became a serious birder about five years ago after bumping into Audubon Society members in the Bay side park and peeking through their scope, said the activity involves a tremendous amount of waiting. More than people might initially expect.

"Most people who go bird watching are pretty against interfering, so it's really an emphasis on observation," New said. " It's a passive observation. We have a difficult time being bored and bird watching – there's a lot of quiet watching and waiting. It's an activity of patience."

While walking around one of the marshes directly across Bayfront Expressway, MacIntosh spotted three black-necked stilts wading in the shallows. She spun around and pointed towards the top of the grassy hill.

"There are the meadowlarks!" she said. About a half-hour earlier she had identified the bird from a different vantage point. In lighting-fast-unison, the walkers raised their binoculars to watch the small birds dive in and out of the tall grass. One teenage boy rifled through his guide book.

"The chance of seeing a rare or uncommon good bird is the appeal," said Cedrik von Briel, a 16-year-old birder who attended the walk. "It's always a treasure hunt, kind of."

Data from the Audubon Society's Christmas Bird Count (CBC), an international effort powered by citizens around the world, shows that the population of the western meadowlark along the California coast has steadily decreased by about 2 percent each year since 1967. By contrast, Canada geese are becoming very common in our area.

According to Farnsworth, bird populations vary tremendously depending on the day, season or year for a multitude of reasons. Canada geese, for example, could be staying in the area for longer than they once did because there are now more resources available to them locally throughout the winter.

"This said, there are changes happening in the species composition as a result of changing climate and habitat," said Farnsworth, though it's not necessarily occurring with the same intensity in all locations. "Birds returning in greater or lesser numbers each year this is the stuff of research that is actively occurring."

When asked how consequential citizen science is to the field of ornithology, Farnsworth used a single word: "Extremely." He then directed me to the eBird site to see for myself.

In 2018, eBird reported that 420,000 users had recorded over 590 million observations. This January, about 250 peer-reviewed publications had drawn from the data since 2003.

"It's very accessible," said New about reporting bird sightings. "You don't have to be a postdoc in ornithology. In recent years, there has been a decrease in western meadowlarks. I'll be driving to work and see one and enter it in."

Von Briel said that he does most of his birding on his walk to school, Woodside High. He enjoys listening to their calls and keeping track of the species he identifies on lists.

The Sequoia Audubon Society provides a list of birds in Bedwell Bayfront Park.

New, who identifies birds when walking between work meetings at Stanford, finds the experience meditative.

"It's not like I set out to look for movement – it's so ingrained in me now," New said. "Every time it brings a smile to my face. You almost feel like you have a secret window into a secret world."

Friends of Bedwell Bayfront Park and the Sequoia Audubon Society's next guided walk through the park is scheduled for Saturday, Feb. 8. Attendees will meet by the parking lot restrooms around 10 a.m.

For more information, email Chris MacIntosh at chrismac@alumni.upenn.edu, or call