~by Jim Eagleman
Field Notes
Jays and Oaks
T
hey fly in, loud and obnoxious, typically in groups of two to four, frightening all other birds at the feeder. You are in for a show of dominance and aggression, not just with other birds, but often among themselves. “Thief, thief” is their call. It’s the blue jay. Like other misaligned wildlife with bad reputations, the jay has a good side. Several, in fact. It’s fall and you have probably noticed that the nut crop on oaks, walnuts, hickories, and beech trees is ripening. Collectively called the Mast, this annual production of nuts, along with seeds and fruits, is a giant pay-off for the wildlife that exploit them. This fall production will feed an assortment of forest wildlife through winter, including deer, turkey, many rodents, crows, and songbirds. The acorn crop alone is responsible for providing a food source for deer, making up as much as 75% of their winter diet. Occasionally white oaks produce an oversized crop of acorns. It’s usually not just one oak here and there, but often in the same year nearly all the oaks in an entire region produce an extraordinary number of acorns. This is called masting and was thought to be an adaptation against acorn predation.
54 Our Brown County • Nov./Dec. 2023
Acorns are a valuable source of winter food for many types of animals. If oak trees predictably produced a moderate number of acorns each year, the squirrels, deer, mice and jays, ducks, towhees, and all other creatures would surely increase their populations. These extra animals would outstrip the food supply and oak reproduction would plummet. But if oaks unpredictably produced many more acorns than the acorn feeders can consume, some acorns would escape the predatory scramble for food, and they would germinate. When jays aren’t at your feeder, you may have seen them fly by with an acorn in their jowls. It’s almost comical. We know they can carry up to six acorns in the mouth—three on either side. Over eons, jays have become so dependent on acorns that they have adapted both physically and behaviorally to acorn shapes. The small hook on the pointed end of a jay’s beak, for example, is designed to rip open an acorn’s husk. The jay’s expanded esophagus (called a gular pouch) enables it to carry them off efficiently. Just because a jay can carry more than one acorn at a time doesn’t mean they take them to the same place.
