The magpies of North America are very visually distinctive from other birds and thus easy to identify. Although the Black-billed Magpie is very similar in appearance to the European Magpie, it is larger and genetically unique. DNA analysis places our two magpies as separate from the European Magpie. Under the same DNA distinctions that the American Magpies were divided from the European Magpies, the Korean subspecies should also be divided as a unique species. The ancestral magpies, after dispersing across Eurasia and becoming isolated in Korea, then crossed over the Bering Land Bridge into the Americas at about 3 to 4 million years ago. Strictly speaking, using DNA comparisons our two magpie species could also potentially be merged as a single species.
Yellow-billed Magpies are a California endemic species that are found west of the Sierra Nevada Mountains in the Central Valley of California. Black-billed Magpies are found east of the Sierra Nevada Mountains, as far north as coastal southern Alaska, and east as far as Minnesota and Iowa. These ranges do not overlap although the Black-billed Magpie tends to wander and may occasionally (rarely) end up south into the northern range of the Yellow-billed Magpie. Normally the two North American magpies are geographically separated and are easy to visually distinguish by bill color. The magpies are part of the Corvidae family, which includes ravens, crows, and jays.
Our two North American magpies sound very similar. They are very vocal and are frequently heard before they are seen. The two most common vocalizations are described as a rapid nasal “yak yak yak” and a second slower and higher pitched ascending call described as “maaag maaag maaag”. The Black-billed Magpie is slightly larger than the Yellow-billed Magpie (19 inches vs. 16 ½ inches in length). Both magpies have extremely long tails and are two of only four indigenous birds in North America that have a tail length greater than their body length (the other two being the Scissor-tailed Flycatcher and the Fork-tailed Flycatcher). Other than the major visual difference of bill color and slightly smaller size the Yellow-billed Magpie also has a variable amount of yellow skin around the eye. It has been suggested that the amount of yellow around the eye may be both genetic and a function of molt sequence timing. The Black-billed Magpie lacks this marking or bare skin around the eyes.
Magpie plumage description
Other than the differences discussed above, Yellow-billed Magpies and Black-billed Magpies are virtually identical. The magpies have a black head, throat, upper breast, and tail. The shoulders, lower breast, and belly are white. The wings, tail and body have an iridescent blue with bronze or green sheen. In flight large white patches show on the primary wing feathers. The bright color contrasts make the magpies very distinctive in appearance and easy to distinguish.
Magpie social habits
Magpies are known to be intelligent and bold. They are also very social birds. Yellow-billed Magpies are significantly more gregarious than Black-billed Magpies. They (Yellow-billed) are more social in their habits, communal in nesting, and roosting. Yellow-billed flocks are even known to exhibit funeral like behavior for their dead. Both birds mate for life and spend year round with their mate. The caveat of this is that divorce may occur! One South Dakota study showed a very low divorce rate for Black-billed Magpies of 8% although another study in Alberta showed divorce rates as high as 63%. It would appear the American magpies show much higher marriage fidelity than the Canadian magpies!
Both Yellow-billed and Black-billed Magpies build a dome over their nest for a nice cozy nursery. Being more social, Yellow-billed Magpies nest in a loose, communal area whereas Black-billed Magpies generally build their nests separate from each other. In the case of both magpies, feeding of the female during brooding is done by the male, and feeding of the young thereafter is shared by both males and females. Being highly social seems to have some drawbacks for male Yellow-billed Magpies. The problem with the communal social structure is that extra-pair copulation is not uncommon amongst Yellow-billed Magpies. After mating, the male will guard the female to prevent her from mating with other males until she actually starts to lay eggs. Makes you wonder what the divorce rate amongst Yellow-billed Magpies is!