There are two particular species of magpies in North America and both of them fascinate me. They are loud like a jay, gregarious like a murder of crows, and yet are beautiful fliers with lots of color flashing to everyone with a naked eye. And the most remarkable feature to me is their tails, which stream behind them for longer than their torso. There are a few species whose tails are long, streaming eye-catchers and one is the magpie. Others include Scissor-Tailed Flycatchers, Roadrunners, and Frigatebirds.
Black-billed Magpies add tremendously to western landscapes, both with their flashy appearance and with their nests. Their color patterns are distinct and their nest hang in trees like a big bushel-basket. Often birders can spot nests in small, loose colonies. In courtship, males pursue females, often flashing their white wing patches.
Nest site sites are usually in deciduous trees from 15-30′ above ground. Nest is a huge structure, a big globular canopy of sticks about 3′ in diameter, with entrance holes on either side. Inside the canopy is a cup-shaped nest with base of mud or manure and lining of weeds, rootlets, grass, and hair. Both sexes help build nest. These birds usually have a nest full of 5-9 eggs, rarely more. The eggs are greenish gray, heavily spotted with brown. The female remains in the nest to incubate the eggs which usually take about 18 days. Male magpies feed the females during egg-laying and incubation period. And both parents bring food to nestlings and the pair has one brood per year. Young magpies have fledged after about 25-29 days after hatching. 
Not long ago, farmers saw the magpie as pests and farmers and ranchers tried to destroy their nests and shoot the birds to exterminate this species. They did not succeed. Today it is common to spot magpies in open country, farms, ranches and even in towns in the mountain west.
The Yellow-Billed Magpie is a boisterous cousin that lives in California, mostly in the Owens Valley and few other places. The species seems to have been stranded from it’s Black-Billed relatives as it resembles it in habits and behavior, despite the difference in bill color. The Yellow-billed Magpie is a riot of black, white, shimmering blue-green, and yellow. It lives in open oak woodlands of the Central Valley, the Coast Ranges, and the Sierra Nevada foothills. This magpie is gregarious throughout the year, even when nesting: dozens of pairs sometimes nest close to each other. A group called “Partners in Flight”  has noticed a serious decline in the subspecies due to habitat loss and West Nile virus. The organization put the species on the Yellow Watch List with restricted ranges.
Feeding Behavior – both species
Magpies seem to be clever diners; they forages mostly by walking on ground; they may use their bills to flip over items in search of food. Sometimes they steal food from other birds, and some birders have reported that magpie follow predators from time to time to pick up any scraps of food that they leave behind.
What does it mean if you spot a magpie flying by? To the average American, the bird symbolizes nothing but loud squawks and dumpster diving birds the size of a crow with long flowing tail feathers. In some western societies, however, the American magpie is generally seen as an ill-omen, and in many eastern communities it is viewed as a positive omen of love. The western societies associate the magpie with witchcraft, magic, divination and prophecy. They are also associated with wight-lore,  and the symbolism of bridges.
 According to wikipedia, a wight (Old English: wiht) is a mythical sentient being, often undead. In its original usage, the word wight described a living human being, but has come to be used within fantasy to describe certain immortal beings.