Guess which local summer bird (male) is orange and black, has a thick bill, and eats monarch butterflies in the winter but doesn’t get sick? If you still aren’t sure, the next hint is … the male sounds like a loud robin on caffeine. You guessed it right; it’s the Black-headed Grosbeak (and I know you didn’t look at the photo). The adult males are brightly colored with a rich orange-cinnamon over most of the body and a patch of lemon yellow on the belly. The black wings have contrasting white bars, while the black tail has contrasting white spots. Females have a brownish head with buff to white or lemon yellow crown and distinct eye-stripe, dull cinnamon to buff body plumage with variable amounts of yellow and sometimes with black streaking. Her brown wings and tail have white bars/spots. Both have grayish thick bills and flash bright yellow under the wings.
This common summer bird is one of our larger, more brilliantly-colored western songbirds that migrate north from Mexico each spring to exploit insects, snails, spiders, fruits, and seeds in our deciduous forests, city parks, and backyards. The large finch-like bird breeds primarily west of the Mississippi and a bit into Canada.
Black-headed Grosbeaks are one of only a few bird species that eat Monarch butterflies which also migrate to Mexico in winter. Apparently this species can tolerate the noxious chemicals that accumulate in these butterflies from their milkweed diet. However, Black-headed Grosbeaks only eat Monarchs in about 8-day cycles, allowing them to rid their bodies of the toxins between feedings.
Another cool fact about Black-headed Grosbeaks is that it usually takes males 2 years to mature and sport their breeding plumage. First year males vary from looking like a female to looking nearly like an adult male. Only those yearling males closely resembling adult males may attempt to breed. The female Black-headed Grosbeak builds a thin open cup nest, usually on an outer branch of a small willow, alder, cottonwood, or other broad-leaved tree or shrub. The nest materials include twigs, weeds, tiny roots, and needles and are lined with hair and other fine plant materials. They lay 2-5 greenish-blue eggs with red spotting.
Male Black-headed Grosbeaks sing their resonating robin-like song from conspicuous perches. To attract females, males also fly with wings and tails spread. Both sexes sing, but have different songs. Black-headed Grosbeaks are monogamous for the entire nesting season; both share in the incubation and other chick-rearing duties. The adults brood the young for about two weeks until hatch and continue to feed the young for another two weeks until fledging. Black-headed Grosbeaks only raise one brood a year. After the nesting season, these birds will group in relatively large flocks and exploit berry crops before heading south for the winter. In Montana, this species arrives in mid-April but is gone by the end of July.
Black-headed Grosbeaks like large, predominantly deciduous trees with a rich understory, such as in groves of cottonwood, aspen or alder and willows along stream margins. In our drier western habitats, they would be associated with pinion-juniper woodlands and oak-savannas. Based on breeding bird surveys across the west, this population appears to be slightly increasing, probably due in part to their adaptation to suburban areas with large shade trees, parks, and feeders, and tolerance to human disturbances. This is certainly one bird that you’ll have no trouble adding to your bird list next summer.
By Gael Bissell of Flathead Audubon