The Yellow-billed Magpie, Pica nuttalli, is a large bird in the crow family found only in California. It inhabits the Central Valley and the adjacent chaparral foothills and mountains. Apart from its having a yellow bill and a yellow streak around the eye, it is virtually identical to the Black-billed Magpie (Pica hudsonia) found in much of the rest of North America. mtDNA sequence analysis (Lee et al., 2003) indicates a close relationship between these two, rather than between the outwardly very similar Black-billed and European Magpies (P. pica); the two American forms could be considered as one species.

However, the Korean subspecies of the European Magpie (P. p. sericea) is more distantly related to all other (including North American) forms judging from the molecular evidence, and thus, either the North American forms are maintained as specifically distinct and the Korean (and possibly related) subspecies are also elevated to species status, or all magpies are considered to be subspecies of a single species, Pica pica.

Combining fossil evidence (Miller & Bowman, 1956) and paleobiogeographical considerations with the molecular data indicates that the Yellow-billed Magpie's ancestors became isolated in California quite soon after the ancestral magpies colonized North America (which probably happened some 3-4 mya) due to early ice ages and the ongoing uplift of the Sierra Nevada, but that during interglacials there occurred some gene flow between the Yellow- and Black-billed magpies until reproductive isolation was fully achieved in the Pleistocene.

The Yellow-billed Magpie prefers groves of tall trees along rivers and near open areas, though in some cities they have begun to nest in vacant lots and other weedy places. A pair of birds builds a dome-shaped nest with sticks and mud on a high branch. They nest in small colonies. These birds are permanent residents and do not usually wander far outside of their breeding range.

These birds forage on the ground, mainly eating insects, especially grasshoppers, but also carrion, acorns and fruit in fall and winter.

The scientific name commemorates the English naturalist Thomas Nuttall.