Just after sunrise on a still-cool July morning, Carla Cicero bushwhacks through a willow thicket in northern California's Lassen Volcanic National Park. A column of sleepy-looking graduate students follows her, many of them hauling packs draped with netting, aluminum poles, and canvas bags. Chirping loudly but unseen in the branches above them are the songbirds they seek. Although Cicero, a curator and researcher at UC Berkeley's Museum of Vertebrate Zoology, is going off-trail, she's following a track rich with history. Eighty years ago, zoologist Joseph Grinnell trekked through this park–and all across California–meticulously describing and collecting the wildlife he found. Cougars and pikas made his list, but also ordinary creatures like finches, mice, lizards, and salamanders. Grinnell eventually surveyed 50 sites in Lassen over a six-year period and collected more than 4,500 specimens.
But Cicero's work is no historical reenactment. Similar research elsewhere in the Sierra and a steady rise in temperatures are fueling scientists' concerns that climate change and other factors may be altering wildlife ranges in the heart of Grinnell's old stomping grounds. To test these theories, Cicero's field team is part of a multi-year effort to retrace Grinnell's biological audit of California's high country. For the last five years, groups from the Grinnell Resurvey Project have covered the state from San Jacinto Peak in the south to the Warner Mountains 550 miles to the north. Instead of relying on computer models or remote sensors, they are climbing peaks, setting traps, and acquiring samples–just like Grinnell did. By collecting from the same areas and comparing new findings to historic notes and drawings, they hope to learn how habitats have changed, which species have vanished, and if global warming is playing a role.
After a two-mile hike, Cicero's team arrives at a clearing near Manzanita Lake and quickly goes to work. Some swing machetes to enlarge the area, while others stake out poles and nets to create a nearly invisible, featherlight barrier 12 feet high and 36 feet long.
Within a few minutes a brown creeper flies blindly into the fine threads–the first capture of the day. Yellow warblers, fox sparrows, Cassin's purple finches, and other species soon follow as the team sets up additional nets around the lake. Researchers identify and count the trapped birds, then either release them or collect them for the museum.
"Grinnell was a genuine explorer," says Cicero, a bird specialist with a doctorate from UC Berkeley. To reach the Sierra's remote locations in the early 1920s, Grinnell pushed his rickety Ford along the region's few dirt roads until it could go no farther. Continuing on foot, he and his assistants followed error-ridden USGS maps deep into the backcountry, hauling shotguns, traps, and cameras to record their finds.
Before Grinnell, no one had so systematically documented California's wildlife. His interest in biology began as a teenager collecting birds near his Pasadena home. At Stanford, his hobby progressed into a scientific career devoted to shooting, trapping, and preserving tens of thousands of small animals, most of which now reside in neatly organized drawers at the Berkeley museum he helped found in 1908. He also left behind 13,000 detailed pages of observations, musings, illustrations, hand-drawn maps, and photos in 35 volumes of journals. "Grinnell preserved data for the future," says Cicero. "He never anticipated all the things we can do now, like DNA analysis and geographic mapping, but he knew it was short-sighted to collect data only for himself." Today, the museum's extensive collections are a gold mine for researchers, and Grinnell's attention to detail enables biologists like Cicero to follow his footsteps with remarkable precision.
Early findings from Lassen indicate that change is in the air. Two-thirds of the park's bird species, including dusky flycatchers and brown creepers, adjusted their ranges in the last 80 years, mostly moving higher. Brown-headed cowbirds, which were absent in Grinnell's time, now inhabit alpine forests, while once-common ruby-crowned kinglets have mostly vanished. But are these changes due to global warming, habitat changes, or new wildlife-management policies? Earlier surveys of Sierra habitat, which began in 2003 in Yosemite, found that many animals, such as piñon mice and pikas, have moved to higher, colder altitudes, possibly in response to the rising temperatures recorded throughout the state.
After a long day of setting nets and trapping birds at Manzanita Lake, Cicero and her colleagues return to their basecamp to swap observations and fill their notebooks with handwritten notes. A few dexterous students skin and stuff the birds they collected that day, preserving them–just as Grinnell did their ancestors–to aid the next generation of wildlife explorers.