The Yellow-billed Magpie is omnivorous, eating a variety of plant and animal foods. Insects, however, make up most of the diet. The Yellow-billed Magpie has been seen pecking insects off the backs of mule deer.
The covered nest requires maintenance to the canopy throughout the nesting season. The Yellow-billed Magpie usually builds a new nest each year, but if a nest fails early in the breeding season the pair will refurbish an old nest for a renesting attempt rather than build a new one.
The oldest recorded Yellow-billed Magpie was a female and at least 9 years, 11 months old when she was found in California.