For example, masting by boreal conifers such as pines and spruce can result in avian population “eruptions” during which various seed-eating bird species are found far south of their normal winter ranges. (Acorn eating was described by one well-known anthropologist as “the most characteristic feature of the domestic economy of the California Indians.”) Interestingly, many of the scientists studying masting in the early 20th century were zoologists whose main interest was the effect of variable seed production on animal populations. Here in California, acorns were a critically important food for Indigenous peoples. Early references date to the Middle Ages, when a common activity during the late fall was to use sticks and clubs to knock down acorns as food for swine when the crop was good. Masting has been of interest to foresters for over 200 years and to farmers and others dependent on the productivity of the natural world for millennia. And it turned out to be a big world: masting species include not only oaks but many conifers and a variety of other taxa, mostly in temperate and boreal regions of the globe (although there is as yet relatively little data from the tropics). Such issues inhabit the world of “masting” or “mast-fruiting”-the production of highly variable and synchronized seed crops from one year to the next. Did that mean trees close by had produced a good crop of acorns? And what about the birds that came back after abandoning their territories? We had no idea where they spent the winter, but presumably it wasn’t far away. Little was known about what factors determine whether it’s a good or a bad acorn year, however. It was well known that the size of the acorn crop varies dramatically from year to year and that this variability is critically important to the demography of many species, including the acorn woodpeckers. These questions eventually led me to a second career, of studying acorn production by oaks, the dominant tree genus throughout much of low- and mid-elevation, temperate California. But where had they gone? How far had they flown to find acorns to eat? And why had the acorn crop failed to begin with? We knew why they’d left: there were no acorns to store or eat during the cold, rainy winter months. But then, the following spring, nearly all the abandoned territories-each roughly seven to 20 acres of oak woodland with one or more granaries in which the birds store acorns-were recolonized, mostly by former group members. It was apparently the end of the study, and possibly of my hopes for a degree. Twenty-four of the 34 acorn woodpecker groups we were following-over 120 painstakingly banded birds-abandoned their territories, leaving a small fraction of individuals to eke out a living over the winter. For the first year since I’d begun studying these group-living birds, as a UC Berkeley graduate student a decade earlier, none of the oaks at our study site bore more than a pathetically poor acorn crop. (Photo by Elaine Miller Bond)įall 1983 brought hard times to acorn woodpeckers in upper Carmel Valley. If you like this, you'll probably love some of my other great freebies like the Leaves Nature Journal or Farming Guided Writing and Handwriting Practice.A variety of oaks. Looking for more Harvest themed activities? Check out my Leaves Unit and Pumpkin Unit Bundles.
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