Deciduous forests are primarily found in the northern half of the world in the Eastern United States and Canada, Central Europe and Eastern Asia. Four distinctly observable seasons distinguish deciduous forests from other biomes, and the plants and animals that live in these areas have developed adaptations that allow them survive the drastic seasonal climate variations that characterise the deciduous forest.
Deciduous trees define the deciduous forest and, in order to adapt to winter water shortages, lose their leaves in the autumn. During the winter months, temperatures drop below freezing, and tree roots can no longer draw water from the soil. Water evaporates from pores found on the undersides of leaves, so if deciduous trees kept their leaves, they'd constantly lose water through their leaves without being able to regain it from the soil. As temperatures cool during autumn, leaf veins on deciduous trees close, trapping sugars in the leaves and resulting in colour changes. When the leaf veins close fully, the leaf drops from the tree. In the spring, new leaves generate and resume photosynthesis, producing and storing energy that the tree will use to survive the winter.
Wildflowers add colour to the forest landscape during the spring and are a common sight in the deciduous forest. While trees occupy the uppermost level of the forest, wildflowers grow close to the ground and, after the leaves of the canopy have fully emerged, don't receive much sunlight as a result. For this reason, many wildflowers found in deciduous forests tend to bloom early in the spring, before the tree leaves have fully developed. These species go dormant during the shady summer and remain dormant through the fall and winter. Other species of wildflowers are shade-tolerate and produce flowers and fruit throughout the summer.
The cardinal, named for its vivid red plumage, is a common songbird species found in the North American deciduous forest. Unlike many other songbird species, which migrate to warmer climates for the winter, the cardinal endures the winter cold, sustaining itself by foraging on the ground, sometimes in groups, for seeds. During the spring, cardinals nest in low shrubs, particularly at forest edges. Males and females are rarely far apart during this time, communicating through their songs as they build their nests and care for hatchling. During the spring, cardinals become highly territorial, so much that they will even fight their own reflection in a window or mirror.
Squirrels are among the most visible and noisiest of deciduous forest mammals, building nests in the hollows and branches of deciduous trees. In the summer months, squirrels can be seen throughout the forest, leaping and scrambling from branch to branch, perpetually in search of food. They have an attuned sense of balance, helped by their large, fluffy tails, and rarely fall or injure themselves in their capers. Squirrels eat just about anything, from nuts and berries to bird eggs, and survive the barren winter by stockpiling nuts and acorns, hiding them in hollow trees or burying them in the ground. When food becomes scarce, they use their keen sense of smell to relocate what they've buried.