Corvids—a family of birds that includes crows, jays, magpies, nutcrackers and ravens—are smart animals. They can make tools, recognize individual human faces and give our five-year-old children a run for their money in solving puzzles.
But now, according to a new paper published in the ornithology journal The Condor, a group of U.S. scientists say that corvids’ unique food-gathering strategies are responsible for replanting many of the forests we have destroyed across the globe.
So, could we somehow “employ” the birds in our reforestation efforts?
Forgetfulness favors forests
It’s well documented that climate change and agricultural expansion have taken a toll on our forests in recent decades. Efforts to repair such damage are often too difficult to implement or too expensive. But not, it seems, if corvids are present.
The birds are “scatter-hoarders,” which means that they wander through large territories to scavenge for fruit, meat and seeds, storing some bits to eat later. But unlike squirrels that stash their loot in one giant pile, corvids hide treats in separate places, occasionally moving them to different locations to prevent other animals from finding them.
While the birds are incredibly intelligent and have excellent visual memories, they can’t remember every single morsel they’ve horded. Each year, a certain percentage of cached seeds go uneaten. Hidden just an inch or two under the soil, these seeds have a chance to take root and sprout in the spring. Via corvids, then, trees are able to spread their seeds into places the wind or rodents couldn’t take them.
In fact, according to the new paper, over millennia many large-seeded trees have co-evolved with corvids. These trees transformed to develop seeds that are carbohydrate-rich so that the birds fill up faster. The corvids, in turn, then became less likely to ingest the seeds on the spot, sometimes carrying dozens of them at a time to locations that are 30 miles or more from where they were initially found.
Not only do corvids plant new forests in areas far from the originals, but the patches they plant tend to be both healthier and genetically diverse. The birds are picky; they often examine the seeds visually and shake them in order to determine whether arthropods or fungi have infested them. The result is that the seeds that get scatter-hoarded are the healthiest ones.
On top of that, many corvids prefer to cache their seeds in recently burned or disturbed landscapes, which are the most in need of reforestation. For example, in California’s Channel Islands National Park, birds reforested two islands. For more than 150 years, grazing, introduced livestock had ravaged the oak and pine forests there. Once the animals were removed in the 1980s, the size of the oak and pine forests doubled in just a few decades, due to the local jays that cached up to 6,000 seeds every year.
Already, in eastern Germany, foresters are tempting jays into planting new trees to regrow a damaged oak forest. They put out seeds for the birds that cache them at the edges of the existing forest. It’s estimated that the jays have been responsible for planting 2,000 to 4,000 healthy, young oaks per hectare in the reforested lands.
Corvid labor has also been proved to save a lot of money. In an urban forest in Stockholm, Sweden, it was calculated that replacing planting efforts performed annually by Eurasian jays with human labor would cost $2 per acorn, or as much as $9,400 over a hectare of forest per year. A fraction of those costs could be invested in maintaining or creating optimal jay habitat, resulting in similar forest maintenance.
Mario Pesendorfer of the University of Nebraska-Lincoln and lead author of the new paper states that the corvids’ capacity to disperse seeds to new areas will surely become even more important for the conservation of oak and pine ecosystems in the future as suitable ranges shift rapidly due to climate change. And since oaks and pines provide habitat for hundreds of animal species, the corvids’ “work” will have far-reaching, positive consequences for an abundance of wildlife.
Once again it seems as though animals may be our best partners in our efforts to conserve our natural world.
Here’s to finding your true places and natural habitats,