Thursday, February 22, 2018

Horned Larks and California's Vanishing Prairie

The word "prairie" probably conjures up images of the vast plains found in the middle part of the North American continent more readily than it is associated with California.  We think of tall grasses, bison, "Little House," and all that.  But many might be surprised to learn that we have our own share of prairie right here in the Great Valley of California - or at least we used to.
Horned Lark at Carrizo Plain National Monument, perhaps the best remnant of San Joaquin Valley grassland habitat.
A vast amount of California's great prairies (also called grasslands) have been paved and ploughed, through urban sprawl and the relentless spread of agriculture.  What remains has been inundated by exotic annual grasses which behave much differently than California's native prairie plant community, the perennial bunchgrasses and forbs (wildflowers and other broadleaf plants) which used to dominate the landscape.   Nowadays, some of the best places to experience California's prairies are along the fringes of the valley, as one drives east or west into the foothills.  Closest to the greater Modesto/Turlock area, there are some lovey backroads northeast of Waterford and south of Knights Ferry that lead adventurous souls into the prairie. 
[Aside: The term "prairie" is actually preferable to "grassland" when describing this ecoregion as the later implies a plant community of just grass, while more accurately it was one of mixed grasses and forbs, with stunning wildflower displays every spring.] 
Vernal pools, one of our most critically threatened habitats, still exist here and there on private land that is largely used as rangeland for cattle.  Spring is the best time to visit these areas, as the grasses are green and with any luck (and rain) the vernal pools fill and ephemeral creeks flow.  As the pools begin to dry up in April, wildflowers bloom in awe-inspiring abundance.  Most of the remaining pools are found in the "higher terraces" in the foothills surrounding the valley.  66% of California's vernal pool habitat is gone forever.
March 2017: an ephemeral creek out on the prairie south of Knights Ferry
Long ago (though very recently in the grand scale of geologic time) before Europeans settled here, the Great Central Valley was a large flood plain with two distinct basins: the Sacramento basin in the north and the San Joaquin basin in the south.  Dividing this great plain were rivers and their corresponding riparian corridors, which spanned several miles on either side of the river.  Upland areas were dominated by bunchgrass prairie, vast grasslands capable of supporting large herds of grazers (most notably tule elk, pronghorn antelope and mule deer) and populations of other herbivores, such as kangaroo rats (some endemic), pocket mice, rabbits and ground squirrels.  Of course, these animals sustained an assortment of predators: gray wolf, coyote, San Joaquin Valley kit fox (also endemic), mountain lion, bobcat, ringtail and grizzly bear.
In California, 99% of all prairie habitat has been lost, and California's grasslands are among the 21 most endangered ecosystems in the United States.
As one might imagine, with the prairies have gone most of the animal species as well.  But what about birds, those winged wonders so often capable of adapting to the human-altered environment?  Horned Larks (Eremophila alpestris) are synonymous with prairies across North America and can still be found in California, if one knows where to look. 
Horned Lark populations have declined sharply in the past several decades.  They forage on the ground for seeds and insects, nest on the ground in woven baskets placed in small depressions, and otherwise rely on areas of undisturbed open grassland for their survival.  Incidentally, developers also hone in on these same open, treeless places as ideal locations for orchards and houses. 
Horned Larks prefer areas of short or sparse vegetation and bare ground.  They manage to do alright for themselves in some human-altered environments - ploughed fields and fields of newly-sprouting row crops, mowed roadsides and airstrips, heavily grazed pasture and feedlots - as these still offer the requisite amount of open space and food sources. 
However, the population lines of Horned Larks crumble at the incessant march of almond orchards as the trees spread (a bit like a bad rash) higher into the foothills, encroaching farther and farther on the remaining prairies.  With advances in drip irrigation techniques, almond, walnut and pistachio growers are able to plant trees on rolling hills, rather than just on flat bottomlands of the valley that were flood irrigated. 
For the birds, this means less and less habitat is available as they are pushed to the fringes of the grasslands.  For me, it means that my frustration grows every time I drive into the hills and see yet another new orchard of thirsty trees planted on previously unirrigated rangeland, while the water outlook in California remains questionable at best.  But I digress.
While there are plenty of miles of open road to explore along the edges of the Great Central Valley, it is rather more difficult to find areas not behind barbed wire fences.  For public access on foot, I recommend visiting Great Valley Grasslands State Park and the adjacent Kesterson unit of the San Luis National Wildlife Refuge, which has a sordid history of its own (another story for another day).  Both of these areas have miles of trails open to intrepid visitors, with very little development in sight.  A little farther north, visitors can walk the nature trail at Jepson Prairie Preserve to see one of the best examples of surviving vernal pool habitat - and maybe even catch a glimpse of a Horned Lark!  Spring is by far the best time to visit these places, as the grasses are green, the wildflowers are blooming, and the weather on these treeless plains remains bearable!
For further reading on California's prairie ecosystem, I recommend Schoenherr's Natural History of California (specifically chapter 10, "The Great Central Valley") as well as the World Wildlife Fund's overview of the California Central Valley grassland ecoregion (link here).


  1. Very nice review of the grasslands! I've had the most success seeing Horned Larks on Willms Road south of Knights Ferry. Looks like you've seen them there as well.

    1. Thank you! And yes, that's a great area. Though I had better luck photographing them at Carrizo Plain last spring than I did along Willms Road!