Species of the Forest

Forests are complex ecosystems. Healthy forests are composed of many species, inter-species relationships, habitat types and ecological processes. Depicted here are just seven species found in western Pennsylvania forests. Each represents a specific facet of forest ecology for conservation and management planning.

Forest Interiors
Neo-tropical Forest Interior Birds
Eastern North America’s forests provide breeding habitat for dozens of passerine bird species that migrate long distances to spend their winters in central and South America. Examples include many warblers, vireos, flycatchers, thrushes and tanagers. Because these birds require deep forest habitats for successful reproduction, they are often referred to as “forest interior” species. Interior forest conditions exist only hundreds of meters away from large openings and edges. Pennsylvania’s forests provide a significant percentage of total breeding habitat for some species. For some species that number is as high as 15-20 percent.

Conifer Tree Species
Comstock’s Sallow (Feralia comstocki)
This attractive moth is associated with conifer coverage in our forests. The caterpillars of this, and the two other Feralia species, are obligate conifer feeders, especially browsing on pines and hemlocks. Therefore, these moths are linked to the historic decline of evergreen trees in forest habitats across Pennsylvania.

Large Intact Forests
Northern Goshawk (Accipiter gentilis)
This large secretive raptor is a denizen of expanses of mixed conifer-deciduous forest. Due to a requirement of more than 1000 acres of forest habitat for a single pair’s nesting, populations of northern goshawk are indicators of high quality contiguous forested landscapes, where it nests in large trees.

Interrelationship of Forest Species
Rose Hooktip
The rose hooktip moth (Oreta rosea) is not normally an unusual species to encounter in many forests of Pennsylvania. However, it is a prime example of the interrelationships between forest species. The caterpillar of this moth feeds almost entirely upon shrubs in the genus Viburnum. Because these plants are favored as food by the white-tailed deer, the decline of these shrubs has meant that several species of viburnum-dependent moths are also now uncommon.

Diverse Habitat
Timber Rattlesnake (Crotalus horridus)
Of all species of rattlesnakes in the world, this is one of the few true forest inhabitants. Once found in 80 percent of Pennsylvania’s counties, it is now reduced to only the most remote regions. For survival, a forest covered slope with deep rock crevices is needed for communal hibernation. Females breed only every third year. Males wander distances of 5 kilometers and more in one summer, largely in search of females.

 

Natural Predators
Lungless Salamanders
One of the richest diversities of salamanders on earth is found in the forests of eastern North America. The lungless salamanders are in the family Plethodontidae, which is the salamander family that includes the largest number of species in Pennsylvania and the world. The 15 species recorded from Pennsylvania use a variety of forest environments from the margins of streams to rock crevices to rich humus on the forest floor. These predatory amphibians feed largely on various invertebrates.

Old Growth Forests
Flying squirrels
Both the southern flying squirrel (Glaucomys volans) and the northern flying squirrel (G. sabrinus) occur in Pennsylvania. These nocturnal squirrel species most often make their nests in tree cavities, especially old woodpecker holes. More mature and old growth forests are most favorable for this habit. The southern species inhabits deciduous forest, while the somewhat larger northern one is found at higher elevations and latitudes where conifers are more abundant.

Photo Credits
Northern Goshawk - Montana Fish, Wildlife and Parks
Canada Warbler - Powdermill Nature Reserve
Rose Hooktip - John Rawlins, Carnegie Museum
Northern Flying Squirrel - Hal Korber
Timber Rattlesnake - E. R. Degginger
Comstalk Sallow - John Rawlins, Carnegie Museum
Red-Backed Salamander - Paul Myers

Go to the next article, Conservation Concepts.