Europe and N. America
"Structurally complex riparian vegetation communities provide many different habitats and support a diverse array of animal species. Different groups of animals occupy or use the different layers of vegetation, and this multi-story arrangement is often present nowhere else in the arid landscapes. Canopies of plants growing on stream banks provide shade, cooling stream water, while roots stabilize and create overhanging banks, providing habitat for fish and other aquatic organisms.
Game birds, squirrels and other rodents, and several kinds of browsers also feed on the fruit or foliage of elderberry. Bears love to eat the elderberry fruits while deer, elk, and moose browse on the stems and foliage. The elderberries are important sources of summer food for many kinds of songbirds. For example, the western bluebird, indigo bunting, common house finch, red-shafted flicker, ashthroated flycatcher, black-headed grosbeak, scrub jay, Stellar jay, ruby-crowned kinglet, mockingbird, red-breasted nuthatch, Bullock’s oriole, hooded oriole, song sparrow, white-crowned sparrow, western tanager, California thrasher, russet-backed thrush, brown towhee, Audubon warbler, cedar waxwing, Lewis and Nuttall's woodpecker, wren-tit, grouse, pheasant, and pigeons all eat elderberries.
The valley elderberry longhorn beetle (VELB) (Desmocerus californicus dimorphus) was listed as threatened under The Endangered Species Act on August 8, 1980. The elderberry beetle is endemic to moist valley oak riparian woodlands along the margins of rivers and streams in the lower Sacramento and upper San Joaquin Valley of California where elderberry grows. The primary threat to the VELB is loss of habitat, insecticide and herbicide use, and lack of elderberry shrubs/trees as a food plant for the beetle. The mitigation for VELB habitat loss, considered a taking under The Endangered Species Act, is quite stringent (U.S. Fish and Wildlife Service Mitigation Guidelines).
In general, longhorn beetles are characterized by somewhat elongate and cylindrical bodies with long antennae, often in excess of 2/3 of the body length. Male VELB have a metallic-green pattern of 4 oblong maculations, surrounded by a bright redorange border. The body length is about 13-21 mm, and antennae are about a long as the body. Females are more robust, with body length about 18-25 mm, and the dark pattern is not reduced.
Elderberry is planted because of its forage and cover value, productivity, adaptability, and ease of establishment. It is a useful ground cover for stabilizing streambanks and eroding sites. It provides food, cover, perching, and nesting sites for many species of birds and food and cover for various other wildlife, and it is important as browse for mule deer and elk. In the spring the leaves may be strongly scented and less palatable, but they sweeten and become more palatable by fall." 
"Edible berries and flower are used for medicine, dyes for basketry, arrow shafts, flute, whistles, clapper sticks, and folk medicine. Elderberries are high in Vitamin C. The active alkaloids in elderberry plants are hydrocyanic acid and sambucine. Both alkaloids will cause nausea so care should be observed with this plant. Warning: The fruit of all elderberries should be cooked to degrade the alkaloid compounds before consuming.
The wood is hard and has been used for combs, spindles, and pegs, and the hollow stems have been fashioned into flutes and blowguns.
Elderberries are quite edible. The blue or purple berries are gathered and made into elderberry wine, jam, syrup, and pies. The entire flower cluster can be dipped in batter and fried while petals can be eaten raw or made into a fragrant and tasty tea. The flowers add an aromatic flavor and lightness to pancakes or fritters.
The elderberry is of well-known value to the Indians of North America and the many purposes it serves. Elderberry is highly prized by both Spaniards and Cahuillas. Throughout the months of July and August the small clusters of berries are gathered in large quantities. These clusters are dried carefully on the drying floor and preserved in considerable amounts. When wanted, they are cooked into a rich sauce that needs no sweetening. A Cahuilla family during this season of the year will subsist largely on these messes of "sauco." Frequently, the elderberry was so greatly enjoyed that families would live for weeks on little else. Many were dried for use in the winter, and were either recooked or eaten raw. Elderberries are still highly prized for food by modern Indian people.
Elderberry twigs and fruit are employed in creating dyes for basketry. These stems are dyed a very deep black by soaking them for a week or so in a wash made from the berry stems of the elderberry. The Cahuilla split basketry materials from the aromatic sumac (Rhus trilobata).
Elderberry branches were used to make the shaft of arrows. Flutes and whistles were constructed by boring holes into stems hollowed out with hot sticks. Clapper sticks were made by splitting the stem and clapping the two halves against each other. Clapper sticks were used ceremonially in the round-house to accompany singing and dancing. The pith of the stems was used as tinder, and the stem itself was employed as a twirling stick for starting the fire. Hollowed-out elderberry stems can be made into squirt guns.
In the middle ages elderberry was considered a Holy Tree, capable of restoring good health, keeping good health, and as an aid to longevity.
Fruits of elderberry are gathered from the wild for wine, jellies, candy, pies, and sauces. The plants are commercially cultivated for fruit production in Oregon. Sambucus canadensis and S. nigra have long been used in the same way, and cultivars of both have been developed. All parts of the elderberry plant are considered to be a valuable healing plant in many folk medicine traditions. Elderberry flowers contain flavenoids and rutin, which are known to improve immune function, particularly in combination with vitamin “C.”
The flowers also contain tannins, which account for its traditional use to reduce bleeding, diarrhea, and congestion. The flowers are the mildest part of the plant and prepared as a tea, are used to break dry fevers and stimulate perspiration, aid headache, indigestion, twitching eyes, dropsy, rheumatism, appendix inflammation, bladder or kidney infections, colds, influenza, consumption (bleeding in lungs), and is helpful to newborn babies. Used as a wash, the flowers or leaves are good for wounds, sprains, and bruises, as well as for sores on domestic animals. The leaves, which are stronger, have a slightly laxative property. Applied externally, leaves, flowers, bark and twigs are excellent as a poultice, mixed equally with chamomile, for soreness, inflammations, joint stiffness, and to reduce the swelling of bee stings. The flowers and berries, employed as a diuretic, can aid arthritis and rheumatism. Steeped in water, the flowers are used externally to aid in complexion beauty, tone and soften the skin, and lighten freckles or spots. The berry juice made into salve aids burns and scalds. The juice taken internally will act as a purgative." 
"Browse rating: Good for goats; good to fair for sheep; good to poor for deer; fair for cattle; and fair to poor for horses." 
 Stevens, M. COMMON ELDERBERRY Sambucus nigra L. ssp. canadensis (L.). (2003). Contributed by: USDA NRCS National Plant Data Center & the Biota of North America Program. https://plants.usda.gov/plantguide/pdf/cs_sanic4.pdf