They're also habitats for wildlife who began life on this peninsula and have no way to really leave it.
Those interests are sometimes in concert, sometimes in competition.
The Presidio is the largest of the islands, and the fact that the 1,400 acres were once an army base with stringent rules about access, populated by a military with a predictable routine, worked to the advantage of local wildlife for many years.
"There weren't as many cats, no off-leash dogs, not as much street traffic." Hopkins says. "Army bases across the country are a lot of our best habitats because of benign neglect."
"Military activities are actually easier for many of these species to deal with than an area with wide public access," says John Anderson, a professor of ornithology at College of the Atlantic who specializes in island avian populations. "It serves as a 'habitat island.' This is why you have nesting birds at the end of the runways at JFK. As long as you get a jet taking off every 30 seconds, it doesn't have much impact. On the other hand, if you have a jet making a low pass over a nesting colony once a summer, it is likely to cause a lot of disturbance."
If there's the equivalent of a jet flying low over the Presidio, it would be the increase of hikers, bikers, park staff, and volunteers regularly traipsing through areas that until recently never saw much action.
And one place that's stood empty and secluded for years is about to see an enormous influx of people.
The Public Health Service Hospital is slated to become condominiums with 250 to 400 market-rate units. It's the largest housing development in the park, and the Presidio Trust is relying on at least $1 million in net revenue from the project: it's a keystone in the overall plan for financial sustainability.
However, the decrepit building is located next to the oldest relic scrub oak habitat in Presidio Hills. "This area has been here since time began," Clark says on a recent tour through that tucked-away corner of the park.
Indeed, the overgrown dunes have an ancient, haunted feel. Listening to the unique song of the white-crowned sparrow, standing among the small scrub oaks and some of the rarest plants in the Presidio, it's possible to forget the nearby high-rises, highways, and houses and imagine a time when the whole western edge of the city was little more than acres and acres of windswept sand and scrubby brush.
"This is the first place I had interactions with park stewards and saw them doing something that worked," Clark says. "They took down a couple of trees, and people complained, but so much diversity popped up where those trees were. Pines can be great and support a lot of birds, but in an intact, native ecosystem they aren't very helpful. This area is a relic, and quail are a part of that relic."
It's clear that this original setting would be perfect for quail and anything else is just a compromise. The soil is loose and sandy, perfect for the dirt baths that clean their feathers. The ground cover is negotiable for their small stature, but there's good shelter and ample food and water.
We're just down the hill from Quail Commons, where the last six Presidio quail live, but there's a lot of unfriendly activity between here and there a road, a fence, a parking lot, and a dump where construction debris is regularly tossed.
"These two areas would be so much more valuable if they were connected," Clark says.
Through the trees that line the hills, it's possible to see the back of the old abandoned hospital. It remains to be seen if more quail will be able to live here among more people and all the things that come with them dogs and cats, trash and cars. Will the new inhabitants take quail education to heart?
As if they're harbingers of what's to come, two joggers with a baby stroller and a dog cruise by.