The 19 cm (7.5 in) long, 47 g (1.7 oz) black-headed grosbeak is a migratory bird, with nesting grounds from southwestern British Columbia, through the western half of the United States, into central Mexico.

Females build nests among the dense foliage on an outer branch of tall broadleaved trees or shrubs, 3–35 ft (0.91–10.67 m) above ground.

The nest is in the shape of an open saucer, made of fine grass, rootlets, twigs, bark, and conifer needles.

The female lays two to five pale green, blue, or gray eggs that are spotted with reddish and dark brown.

In their wintering grounds, this grosbeak consumes many monarch butterflies, perhaps over one million per year in the overwintering colonies in Mexico.

[3] The same genetic changes that confer resistance to the poisons in the monarch and its relatives were found to have evolved in the black-headed grosbeak in a case of convergent evolution.

Two of the grosbeak's four copies of the gene encoding this protein have changes that are also found in insects adapted to feeding on plants producing the cardiac glycosides.

Black-headed grosbeaks range from the Pacific Coast to the middle of the US Great Plains and from southwestern Canada to the mountains of Mexico.

When feeding the chicks sing to their mother, rustling wings and displaying their yellow under-feathers (see image).