The lives of many forest inhabitants are intertwined – sometimes in fascinating and unexpected ways. Consider how Blue Jays (Cyanocitta cristata), beech trees, bears, and a complex disease of beeches are interconnected. Blue Jays, like their nutcracker cousins, gather seeds from trees and cache them for winter use. Nutcrackers focus on pines; the jays on oaks and beech. Jays extract up to a dozen beech nuts from the tree-top burrs, hold them in their expandable throats, and fly, often several miles, to where they roost, nest, or breed. Frequently, these places support conifers. Dropping to the ground, the birds disgorge the nuts and then proceed to hide them beneath the litter, singly, in different spots several yards from the pile. Conifer trees, rocks, and other winter-visible features serve as memory cues or beacons to help relocate the cached seed. Nuts that escape being retrieved are ideally situated to germinate and eventually become trees. Often groups of beech trees are a family, having come from the same parent tree.
By this means, Blue Jays introduce, reintroduce, or redistribute groups of beech seed with such genetically determined traits as form, growth rate, and susceptibility or resistance to insects and disease.
Beech bark disease is a lethal or disfiguring disease of beech caused by the combined actions of a tiny scale insect and bark-killing fungi. The insect and one of the fungi were accidentally introduced to Halifax, N.S. before 1890. In northern New England, New York, and the Maritimes where the disease is most severe, groups of disease resistant trees occasionally occur. Genetic studies reveal that trees in groups are families and distribution patterns suggest that they were “planted” by Blue Jays. Thus, these birds influenced the structure of the beech forests and determined the patterns of resistance or susceptibility.
Beech bark disease reduces tree vigor and nut production. Beech nuts are highly desired – in some northern areas critical – for wildlife. For example, unless they gorge on fat- and protein-rich nuts before denning, female black bears cannot bear young. In some northern regions of Maine, the normal two-year seeding cycle has entrained the reproductive cycle of bears. Beech bark disease has affected this relationship and black bears will often travel long distances to where groups of disease-free trees are seeding – groups of trees that owe their origin to the activity of winter-savvy Blue Jays. It’s a complex world.