The role of a species in the community, like the job and social function of a person, is its _niche_. Similar species of animals have different niches, thus lessening competition for food and living space. Thrushes hunt close to the ground; vireos and kinglets hunt among the branches; flycatchers snap up airborne insects. The flicker feeds upon insects, excavates nesting holes that are later occupied by other species such as squirrels and owls, and is preyed upon by the great horned owl; its niche is _insect exterminator / food for carnivores / homebuilder_. The great horned owl, hunting mammals, birds, and reptiles by night, preys on species different from those hunted by the goshawk, and thus occupies a parallel niche. When it dies, its remains, like those of other animals, are decomposed and return to the soil.] Canopy Great Horned Owl Yellow-bellied Sapsucker Understory Flying Squirrel Shrub Layer Ruffed Grouse Herb Layer Red Squirrel Western Toad Forest Floor Shorttail Weasel Scavenging Insects Deer Mouse Garter Snake Soil Layer Ground Squirrel Earthworm Masked Shrew [Illustration: Sun, Green Plants, and Animals The sun is the source of energy for any plant-and-animal community. Green plants draw nitrogen and minerals from the soil, and in a process called photosynthesis use sunlight to convert raw materials (carbon dioxide and water) into carbohydrates (sugar, starch, cellulose), giving off oxygen as a by-product. Besides burning oxygen, animals depend on plants for food. Green Plants, trees and shrubs, grasses and sedges, wildflowers, ferns, mosses, algae and lichens—are fed upon by animals, which are unable to manufacture their own food. The Redback Vole, like other rodents, pikas and hares, seed-eating birds, grazing and browsing hoofed animals, and herbivorous insects, derives its energy from the seeds and other parts of green plants that it eats. The Garter Snake, feeding upon the vole, is dependent upon plants even though it does not eat them. The Great Horned Owl, preying upon the garter snake, is one more step removed from the green plants—but still dependent on them. Scavengers such as carrion beetles feed upon the carcass of the owl; the remains are then attacked by Decomposers, primarily bacteria, that break down the animal tissues into basic organic compounds. The Soil, enriched by the minerals and carbon and nitrogen compounds added to it by the decomposers (and by other processes such as fire) supports new green plant growth. Thus energy derived from the sun flows through the ecosystem in a food chain. A plant-and-animal community is a complex, interlocking web of such food chains.]