Yellow-billed Magpie Life History

Habitat

Habitat Open Woodlands

Yellow-billed Magpies are permanent residents in open oak woodlands and grassy oak savannas of central California. Like most corvid (crow family) species in North America, they have adapted to human-modified habitats in many places, including some suburban areas. They forage and nest in agricultural areas and pastures that feature tall trees for nesting; also in riparian areas, orchards, and lower foothills, so long as there are insects and water available year-round. Common tree species in Yellow-billed Magpie habitat include valley oak, blue oak, coast live oak, western sycamore, gray pine, Monterey pine, Monterey cypress, black cottonwood, Fremont cottonwood, blue gum, black locust, and various species of willow.

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Food

Food Omnivore

Like crows and other magpie species, Yellow-billed Magpies feed largely on the ground, taking insects and other invertebrates along with plant matter such as acorns and grain. They also eat trash, dog food, roadkill and other carrion, nestlings, eggs, and live rodents, which they hunt on foot, from the air, or from a perch. Yellow-billed Magpies are visual hunters, walking along until they spot food, then quickly seizing prey with the bill or picking seeds or grains from the ground. They also forage in trees, particularly on insects, and even pursue insects in flight. After heavy rains, Yellow-billed Magpies feed on earthworms brought to the surface. Like ravens, they sometime flip over dried cow manure to eat cutworms and other insects. Their well-studied diet includes hundreds of different species of larval and adult butterflies, moths, grasshoppers, ants, bees, beetles, bugs, flies, and spiders. They also eat arthropods such as ticks, sometimes picking them off deer or horses. Acorns, seeds, nuts, fruit (wild berries, grapes, figs) and grains such as wheat, oats, barley, and sorghum are also part of the diet from late summer into early winter. When food is plentiful, Yellow-billed Magpies cache (hide) excess food items, usually returning within a day to retrieve and eat the item.

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Nesting

Nest Placement

Nest Tree

Nests are set high up (average 47 feet) in large trees, often in a clump of mistletoe. Pairs sometimes reuse the previous year’s nest.

Nest Description

Both male and female spend a period of weeks building a very large nest—nearly 3 feet across. They use large sticks for a base, which they cement together with mud and cow or horse dung, then line with hair, grass, bark, and roots. Over the top of the nest, they make a dome or canopy of sticks.

Nesting Facts

Clutch Size:4-7 eggs
Egg Description:

Greenish blue or olive with dark spots and speckles.

Condition at Hatching:

Naked and helpless.

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Behavior

Behavior Ground Forager

Yellow-billed Magpies form long-term pairs that appear to be monogamous, though occasionally courtship or copulation may occur outside the pair bond. When the time for nesting approaches, the male and female stay close together, and males commence courtship by slowly walking around the females, fluffing up the plumage and adopting an upright stance, calling, and quivering the wings. Although Yellow-billed Magpies nest in loose colonies, very near other pairs, the male of a pair is generally intolerant of other males approaching the female during this period. He may chase off other males, begin a parallel walking display, or attack. Both male and female build the nest; females do more of the work of lining the nest. During this period, females remain in the nest tree for long periods, begging food from males, which males deliver once the female lays the first egg. Both parents share incubation and chick-rearing duties. They maintain their bonds by nibbling on each other’s bills and preening each other’s napes. Males often perch conspicuously during the nesting period, watching both for rivals and predators, and some males also perch high in the nesting territory during winter mornings, perhaps to continue their claim on the nest territory. After nesting, families gather into large flocks and remain together over the nonbreeding season, foraging during the day and roosting overnight together. Larger summertime flocks are probably composed of nonbreeding 1-year-old birds.

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Conservation

Conservation Restricted Range

According to the North American Breeding Bird Survey, Yellow-billed Magpie populations declined by an estimated 2.9% per year between 1968 and 2015, resulting in a cumulative decline of 76% during that period. Partners in Flight estimates a global breeding population of 110,000, rates the species a 16 out of 20 on the Continental Concern Score, and includes it on the Yellow Watch List for species with restricted range. Yellow-billed Magpies are still sometimes trapped and shot in rural areas, especially cattle operations. They have also declined precipitously in areas where rodenticides were used. During the height of the West Nile virus epidemic, in the early 2000s, scientists estimate that Yellow-billed Magpies lost half their population. Perhaps the greatest threat to the existence of this species is habitat lost to development in California’s populous Central Valley.

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Credits

Koenig, Walter D. and Mark D. Reynolds. (2009). Yellow-billed Magpie (Pica nuttalli), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

Lutmerding, J. A. and A. S. Love. (2019). Longevity records of North American birds. Version 1019 Patuxent Wildlife Research Center, Bird Banding Laboratory 2019.

Partners in Flight (2017). Avian Conservation Assessment Database. 2017.

Sauer, J. R., D. K. Niven, J. E. Hines, D. J. Ziolkowski Jr., K. L. Pardieck, J. E. Fallon, and W. A. Link (2017). The North American Breeding Bird Survey, Results and Analysis 1966–2015. Version 2.07.2017. USGS Patuxent Wildlife Research Center, Laurel, MD, USA.

Sibley, D. A. (2014). The Sibley Guide to Birds, second edition. Alfred A. Knopf, New York, NY, USA.

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