Crocker-Amazon Wildlife and San Bruno Mountain: Reflections from San Bruno Mountain Watch Boardmember Dr. Rosalyn Johnson

South San Francisco, CA   November 6, 2019 Submitted by San Bruno Mountain WatchSan Bruno Mountain Watch


Reflections from Dr. Rosalyn Johnson, SBMW board member

We’ve only had a few light rains so far in Crocker-Amazon, the sloping neighborhood at the farthest reach of San Bruno Mountain’s northern hill.  The hill under Crocker-Amazon has been graded and leveled in places, so it’s original topography has changed some. It has long been covered with San Francisco and Daly City houses, although it is still topped with protected and managed parkland in a natural state. Figure 1 (below) shows the slope that leads up to the County and State Park.
Photo by Tim Adams.
Houses cover the mountain’s contoured flank but the hilltop forms part of
the County and State Park systems.
Portions of the Excelsior, Crocker-Amazon, and Southern Hills neighborhoods are shown.
From most of the neighborhood you can see an overlook on the Saddle Trail in San Bruno Mountain State and County Park. It’s a high point on the hill with no houses where you may spot the occasional band of hikers admiring the view. The view from the overlook appears in Figure 2.
Some of the mountain’s animals still utilize the neighborhood as a different sort of habitat than that of the wild mountain. Coyotes, for example, are frequently seen around according to neighbors on Some of the animals here are so common in cities that they would be here even without a natural area nearby (for example, sparrows, rats and pigeons).  See Figure 3 for the species list I’ve made so far in Crocker-Amazon just walking around and in one Daly City garden.
When the rains arrive here all the weedy plants and CA native plants will start to grow again, both in the neighborhood and on the mountain. It’s the best time to get your garden started while the natural clay soils are soft and young plants can get moisture from the rain.  Establishing CA native plants at your homestead on Crocker-Amazon hill is a way to support populations of songbirds and wild native bees and the other pollinators, too.
This landscape changed the living conditions for insects and wildlife when people developed it.  For some insects, when their food plants disappeared from the area, so did they. As they went, so went the birds that fed on them. Of course, this is not a pattern that is unique to Crocker-Amazon. It is repeated many places that people live in the United States, but this habitat loss is part of the reason that bird and insect populations that have been monitored for years are falling. Pesticides and poisons that kill creatures that they do not target are another problem for those non-target insects and wildlife.  When predators become secondary deaths to rat poisons, for example, the remaining prey (or pest) population is harder to control naturally because there are fewer predators.
Turning these trends around means that your kids and your grandkids might see some of the common butterflies that we saw as children if we can bring them back.  It’s not your imagination; there really are fewer birds and butterfly species and fewer individuals of those species around now. We humans have changed enough natural habitats to suit our uses that the nature that was beginning to fray at the edges is now showing tears, globally. The information is out there in scientific papers and there is growing concern. You can Google insect and pollinator declines, milkweed loss and threats to the monarch migration, falling songbird numbers, expected threats to wildlife from climate change, and more. Sometimes it’s overwhelming how much information there is on topic. If we do nothing, declines will simply continue.
Fortunately, even without knowing all the particulars of these declines there are things that we can do now to support nature locally. We can demand protections and good management for remnant natural areas like San Bruno Mountain. And, we can improve urban habitats. Why focus on urban areas? In addition to this being where we are, so we have some control over what happens around us, urban habitats are less exposed to agricultural pesticides and herbicides than rural areas where they are more commonly applied. A surprising number of pollinating insects and bird species still share urban areas with us though several species are fewer in number and some species have disappeared. I work in this urban area to help people to put a bit of nature (in the form of local native plants) back into their yards to support pollinators and wildlife.
If you incorporate native plants into your landscaping you can support pollinators like bees and beetles that will feed on flower nectar and pollen and support butterflies and moths by planting their host plants. I mentioned before that when their plants left their creatures followed, but nature is resilient.  Bees still visit ornamental flowers, but they will also visit native flowers that you add. Birds may capture a caterpillar or two from the host plant that you plant and maintain, but some caterpillars will pupate into butterflies that will mate and lay eggs again. It’s a powerful thing bringing the natural cycle back to your yard, especially here, close to a natural protected area.

This rainy season consider adding some native plants to your landscaping to help the wild bees, butterflies, and the birds. Check out the SBMW butterfly poster for more ideas for host plants (large and small) for butterflies, and stop by the Mission Blue Nursery plant sale on November 23rd. Experienced staff and volunteers will be there to answer your questions.
If you are like me and live in Crocker-Amazon or on another slope of the mountain, planting locally-sourced native plants will be a small act of habitat restoration. Just one native plant, especially a shrub or a tree, can make a difference for native pollinators and wildlife. They deserve our support if we want to keep the birds, bees, and other creatures around.
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