Western Bluebirds tend to perch fairly low to the ground on prominent limbs, fence posts, and signs. They also tend to stay low to the ground when flying. They forage for insects by scanning the ground from a perch, then abruptly dropping to seize something they’ve spied. Outside the breeding season, Western Bluebirds are quite social, forming flocks up to about 100, sometimes with Mountain Bluebirds, American Robins, and Yellow-rumped Warblers. Their tree-cavity nest sites are a limited and valuable resource, and Western Bluebirds have to contend with competition from other bluebirds, swallows, nuthatches, some woodpeckers, House Wrens, and European Starlings. Western Bluebirds appear to be monogamous—one male pairs with one female to raise young each year. But experiments reveal that up to 45 percent of nests contain one or more young that are not the resident male’s offspring. Sometimes at nests, Western Bluebird pairs are joined by helpers who assist in raising the young. These are often adult males, but also include adult pairs and young birds.