Oak Trees and Wildlife

One of the most beneficial trees for wildlife is the oak tree. Oaks offer food, shelter, cover, and nesting sites for a number of animals. The branches, nooks, crannies, and hollow areas in oak trees afford protection from the elements, a place to rest, escape predators, and nesting areas to raise the young. Many animals feed on the small twigs, buds, shoots, and leaves of oaks as well. Oak trees attract hundreds of insects and invertebrates that feed on their foliage. These insects attract insectivorous birds, reptiles, frogs, and mammals developing a very dynamic food web within the forest. Because oak trees attract such a wide variety of insects they are considered to be one of the most important trees for woodland inhabiting birds. Oak trees also produce acorns which are a very important winter food for deer, fox, bear, squirrels, turkey, wood duck, and many birds. Animal populations tend to increase or decrease based on yearly acorn production a testament to the importance of oak trees. As oaks mature they typically produce more acorns and develop a large hollow area which further enhances their value for wildlife.

Oak trees tend to be longer lived, slower growing trees that develop best in full sunlight to moderate shade. Acorns may be able to germinate and develop a small tree in dense shade, but the oak tree will cease growing in shady conditions, waiting until it can exploit a gap in the canopy and continue its development. In this holding pattern the small oak trees are vulnerable to deer browse or they may eventually succumb to lack of sunlight. Trees such as red maple, black gum, hickory, beech, sugar, maple, black birch, and hemlock can develop much better in the shade and they will overtake the young oaks underneath a dense canopy. Many of the oak forests we now have are a result of former land clearing and logging practices that created conditions beneficial to oak germination and growth. In the past large forest fires were also much more common throughout our region which gave rise to more oak regeneration. The thick bark oak tree is more resistant to forest fires and they are more likely to continue growing when the thinner barked maple, beech, birch or white pine tree may succumb following a forest fire. Oak and oak-pine forests are considered to be fire dependent communities by ecologists. Many of our present oak forests contain trees in their golden years and the understory is full of shade tolerant maple, birch, gum, and beech trees. In ecological terms an oak forest is considered to be intermediate while a beech birch maple forest is considered to be a climax forest community. This means that in the absence of disturbances as the older oaks succumb to old age the forest composition will change and the forest will contain more maple, birch, beech and gum, and less oaks. And, the prevailing trend seen throughout the east is that oak numbers are indeed declining. Along with changes brought about by forest succession, factors such as gypsy moth mortality, oak decline and other diseases, feeding activity of white tail deer, logging operations that remove oak and little else, forest fragmentation, and invasive plants that overrun the forest thereby suppressing most native plants are all contributing to the decline of oak trees.

To understand how intricately nature interacts it has been shown that a reduction in the amount of oak trees is impacting numerous forest interior bird species including the wood thrush and wood pewee. Many of these species are displaying sustained population declines of 3% - 4% per year. Other factors contributing to this decline include loss of habitat from forest fragmentation, increased mortality, nest parasitism, overabundance of deer, cell towers, wind turbines, and acid rain.

Lighting a controlled burn of the pine swamp, Frederick City Watershed

Credit: maryland.gov

Recognizing that the gradual loss of oak canopy may impact future wildlife populations, plant diversity, and the forest products industry many foresters, wildlife managers, and forest ecologists etc. are attempting to encourage the retention of oak forests or the establishment and development of oak tree regeneration where it is suitable to do so. In the fall of 2019 a prescribed burn was conducted at the “Pine Swamp” area on the Frederick City watershed. The purpose of this controlled burn was to encourage pitch pine, shortleaf pine and oak development by controlling the thin barked maple, beech, and birch trees that had colonized the site while reducing fire danger by eliminating some of the downed fuels that were scattered around the site. The burn was deemed a success and preliminary evidence suggests that numerous young pine and oak trees are developing in the area that was burned in 2017. Besides these “silvicultural” practices to encourage oak regeneration, landowners can plant oak seedlings, and protect their oak trees from destructive insects like gypsy moth to help maintain this majestic tree on our landscape.

Article by FCFCDB

Nature Note for 5/9/20