Bird count results suggest effects of global warming on local populations

by Ryder W. Miller

The results of the annual Audubon Society Bird Count suggest local bird populations are facing the effects of global warming, and some species are facing extirpation.

As well, as of presstime it seems as if there is not going to be a traditional winter this year.

"When you see 30 swallows in SF right after Christmas and hundreds in places like the Las Gallinas Sewage Ponds in San Rafael, you  have something going on. And when you have something similar going on for several years, you can start to think about the possibility that something like climate change might be at work here," said Dan Murphy, a Sunset District resident and tabulator for the San Francisco Bird Count.

"Is it a fake spring?" Murphy asked. "We're seeing migratory birds creep on the calendar. Allen's Hummingbirds and Tree Swallows are two species that are showing up earlier than they did historically. In fact, Tree Swallows and Violet-green Swallows have been present all winter. Does that mean they will winter here in the future? Looks like a possibility. So, a drought in January won't mean much unless it's part of a climate change. Then it's significant and we'll see changes in bird populations for sure. Otherwise, it's probably something that happens every once in a while and the birds will be OK with it."

Though not a rigorous scientific experiment, the annual count does give birders and environmentalists a sense of the trends that are occurring in the area. The count has also identified threats to birds "posed by feral cats and unleashed dogs in many of our parks."

The assembled bird counters surveyed all the birds they could find in a 15 mile radius from an area near Lake Merced. The area encompasses from about 5 miles offshore of Fort Funston to the west, and to the San Francisco Bay to the east. The southern border of the count was San Bruno and to the north it was the Golden Gate Bridge. Audubon reports that the birding teams counted avian populations in 16 areas on land, but had only one boat to cover the Bay.

The Audubon Society's press release for the bird count shows the scope of the effort.

"From the dark hours before dawn until dusk, teams of birders will scour the northern peninsula for some of the winter's most beautiful treasures - the birds that winter on the land, in the Bay and on the ocean," the release said. "This is one of more than 2,150 similar counts taken from Guam to Labrador and from Alaska to Chile during the period of Dec. 14, 2012 through Jan. 5, 2013."

There were 112 observers in the field this year for the San Francisco area count, with 175 species with 55,274 individuals being seen. The species count was down two and the individual count was down 5,500 from last year.

"We had 10 Violet-green Swallows and 20 Tree Swallows ... seen in the Bay Area during the winter. That's pretty unusual and of all the birds we have on the count, I think their presence this year, and the continuing presence of various swallow species during recent years, most suggests a change in our climate," Murphy said.

Of concern are the loss of species restricted to rocky shorelines. Ruddy Turnstone are most likely gone from the coast, but are still found occasionally on the Bay. Surfbirds and Black Turnstone are species which had lower numbers than in recent years.

Surf Scoters are down in the same period from an average of 5,422 to 1,298 during the past five years. In 2012, they only counted 457, an alarming drop in numbers. Since the San Francisco Bay and the surrounding ocean waters are the central part of the Surf Scoter's winter range, the drop in numbers is considered alarming.

Clapper Rail habitat may be limited to only Herons' Head Park near Hunters Point, where only two were seen this year.

Though coastal scrub birds are a concern this year, California Quail were counted at 50, which was one of the highest counts in recent years. Bewick's Wren, Wrentit and Spotted Towhee are on the verge of extirpation.

"Brewer's Blackbirds hit an all-time low as did Mourning Doves," Murphy said. "That's a really serious drop in their numbers. I have no idea what's going wrong for them." 

Crows were up from last year to 523. and ravens were counted at a record 805. Both birds are opportunistic feeders that can adapt to urban development. Murphy said feeding them increases their numbers and he remembers that not too long ago they were not in the western part of the City.

In related neighborhood news, the Great Blue Heron Project at Stow Lake in Golden Gate Park is celebrating its 20th anniversary this year.