Rare Purple Martin birds — and locals — return to Mount Umunhum outside San Jose

The purple martin bird, an iconic fixture of East Coast backyards, has a little-known Western hideout: the summit of Mount Umunhum in the Santa Cruz Mountains outside of San Jose — the former site of an Air Force surveillance center, and the future site of a recreational area.

“It’s one of those situations where no one was really up there looking around, and we didn’t realize the birds had been there all the time,” said San Francisco Bay Bird Observatory biologist Alvaro Jaramillo of the rediscovery of these social, plum-purple migratory birds.

mt umunhum tower
The radar tower at Mt Umunhum, built for the Almaden Air Force Station, peers through the mist, on Feb. 7, 2014. (Faine Greenwood/Peninsula Press)

Environmentalists hope the discovery of the rare birds will boost public interest in the site, as officials complete its transformation from a former Air Force station laced with toxic chemicals into a new addition to the Midpeninsula Regional Open Space District.

The purple martin was thought to be practically gone from the Bay Area until it was spotted in 2011 by researchers gathering data for an environmental study of the site.

It’s unclear how many birds reside at the site, but as many as 15 of the martins — a dramatically colored and gregarious member of the swallow family, with acrobatic flying abilities — have been spotted at the summit at any given time.

A seasonal species, the purple martins reside at Mount Umunhum for a few months in the spring, likely spending the colder months on extended vacation in South America, said Jaramillo

Now, biologists with the Midpeninsula Regional Open Space District plan to encourage the birds to move into man-made nests, where respectful visitors can view them, as well as the other wildlife, from mountain lions to golden eagles that populate the pristine reserve.

Most purple martins “nest in natural cavities here in California and that’s unknown right now on the East Coast,” said Jaramillo, who will be working to encourage the birds to take to the man-made boxes in the hopes of expanding the local population.

Purple martins are native to both the East and West Coasts of the United States, but are much more common back East. In these cooler climates, the birds now live in man-made communal nesting boxes, a common fixture in Eastern backyards.

Western purple martins still nest in natural crevices, but there’s precedent for human assistance with their life cycle: Native Americans in California historically encouraged the birds to nest inside of prepared gourds, perhaps because the purple martins devoured insect pests — or were simply nice to look at.

On a recent Friday, eight volunteers for the Open Space District made the winding trek up the mountain in drizzly conditions to help erect the first bird boxes for the Mount Umunhum population.

“This is such a special mountain, and people have been watching it for years,” said volunteer and Half Moon Bay native Lynn Jackson of the new efforts to open up the summit, as she took a break from the damp business of setting up bird boxes.

Volunteers dig postholes for purple martin bird boxes at the summit of Mt Umunhum near San Jose, on Feb. 7, 2014.
Volunteers dig postholes for purple martin bird boxes at the summit of Mt Umunhum near San Jose, on Feb. 7, 2014. (Faine Greenwood/Peninsula Press)

“They’re doing all this in order to have a place for the birds,” said Jackson, approvingly, as she watched two volunteers mix cement, while others looked over the new, custom-made cedar boxes that will provide the martins with man-made lodgings.

A former Air Force controlled area, the site where the birds live was purchased for redevelopment into a nature preserve in 1986. But there were no funds to clean it up. The buildings that used to host a small community of Air Force families were full of dangerous asbestos and lead paint, although occasional, uninvited urban explorers passed through the area.

That all changed in 2009, when the site’s public affairs manager finally secured a $3.2 million federal appropriation to clean up the old infrastructure.

“When that old infrastructure was up there, it was dangerous,” said Meredith Manning, interim planning manager for Midpeninsula Regional Open Space District.

Now with the hazardous cleanup done, the management of Mount Umunhum is looking ahead to a considerably more pristine future.

A combination of taxpayer funding and a $1 million grant from the Coastal Conservancy will provide means to construct recreational trails and interpretative areas at the summit for public usage.

Bay Area residents will likely be allowed into the site as early as the spring of 2017.


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