Black-headed Grosbeaks nest in most deciduous and mixed wooded habitats away from southwestern deserts. It is partial to oak and pine-oak habitats but also occurs in riparian lowlands with cottonwoods and dry pinyon-juniper slopes. This species preys in insects, including butterflies, and eats berries and seeds. Migrants may turn up in any wooded habitat.
Casual during migration and winter to the Midwest and Est. BNlack0headed hybridizes occasionally with Rose-breasted in range overlap on the Great Plains.
VOICE SONG and CALLS similar to Rose-breasted Grosbeak but slightly higher; song more rapid, less flowing
The Black-headed Grosbeak is one of the few birds that can safely eat the poisonous monarch butterfly.
Their nests are so thinly constructed that eggs can be seen through the bottom. However, nests are less thin in northern California. Thin nests may provide ventilation and help keep them cool.
They hybridize with their eastern counterpart, the Rose-breasted Grosbeak, along their mutual boundary. This situation arose when the treeless prairies, which once formed a barrier between the two, became dotted with towns and homesteads, providing suitable habitats for both species.
A group of grosbeaks are collectively known as a “gross” of grosbeaks.