Foraging and Population Ecology of Steller’s Jays in Redwood Forests: Implications for Marbled Murrelet Conservation
On any given summer day in the heart of California’s old-growth redwood forests, at any number of campgrounds, you might find visitors marveling at the towering giants, enjoying a picnic, and being entertained by charming guests.
The guests are the curious and clever native birds, Steller’s jays.
A little breadcrumb here, a dropped potato chip there may not seem like much. And it’s entertaining to watch a bird pluck your lunch right out from under you.
But a five-year study led by Elena West and Zachariah Peery from the University of Wisconsin, and sponsored by Save the Redwoods League and other organizations, has proven that Steller’s jays’ appetite for human food is a major problem.
The study had West and her team tracking the foraging patterns, diet, and their effects on Steller’s jay populations in four parks in Central and Northern California. These sites were chosen not just for their large populations of Steller’s jays, but because of another native inhabitant—the marbled murrelet.
The marbled murrelet is a federally protected native seabird that nests in stands of old-growth forest. While the Steller’s jay is out entertaining campers, the shy murrelet is hiding from these natural predators.
West believes the Steller’s jay human-food addiction presents a major challenge. “They’re incredibly intelligent, they’re good learners, and they have great spatial memory. And because they’re omnivores, they can eat a range of food, including food left out by humans. We also see jays adapting to areas where humans are living, which has allowed their populations to expand.”
And in fact, that is just what they are doing. West’s study found that between 35 and 50 percent of the diet of jays in sampled campgrounds was made up of human food, increasing over the summer months when campground visitation is at its highest.
But it’s not just a little free food that’s the worry. These eating habits are altering the very ecology of the entire ecosystem.
West and her colleagues found that Steller’s jays are changing their foraging patterns and their territory sizes, allowing for more jays to occupy the same given area, increasing risk to marbled murrelets.
The marbled murrelet suffers from other environmental stressors, including too few nest sites because of lost old-growth redwood forests and reduced availability of ocean fish which is their preferred food. While these issues are difficult to solve, park visitors can help lessen the risk to marbled murrelets from Steller’s jay predation by keeping all human food away from wildlife.
If successful, we can help prevent extirpation of the marbled murrelet in the Santa Cruz Mountains and maintain the delicate balance of species in the coast redwood forest.