On the wild side—May, 2012
by Tina Mitchell
Members of the Cardinalidae family along with cardinals and buntings, male Black-headed Grosbeaks arrive from their wintering grounds in Mexico a bit before the females do, generally in early May. Their lovely, lilting, slightly buzzy songs—which some say sound like an operatic American Robin—rings through our area until late August or early September. Birds in the southern parts of their range stay year-round; Colorado birds likely winter in Mexico. Black-headed Grosbeaks choose a wide variety of different habitats for breeding, generally at altitudes between 5,000 and 8,000 feet. In Colorado, they have been documented in riparian (river) forests, scrub oak, pinyon/juniper, aspen and ponderosa pine, to name just a few. A decidedly western bird, Colorado hosts only about 3.2% of the breeding population, coming in sixth behind California, Oregon, New Mexico, Washington, and Arizona.
Males and females look quite different from each other: Males (see photo above) show off striking black, white, and rufous colors with lovely lemon yellow under their wings, while the females—especially in comparison to the males—are rather drab with brown streaks on a warm, buffy background (right). Officially entitled Pheucticus melanocephalus, the species name seems obvious—from Greek for “black” (melano) and “head” (cephalus). But the genus name Pheucticus—“painted with cosmetics”—is a bit odd. It likely was first applied to the Rose-breasted Grosbeak—a very close relative of Black-headed Grosbeaks—which has a brilliant red “bib” on its otherwise white chest. The common name—grosbeak—derives from French for “large beak,” which indeed they have.
About 60% of their diet is insects and spiders; the rest, fruit and seeds. On their wintering grounds, they are one of only a few species that eat Monarch butterflies, despite the fact that Monarchs contain toxins deadly to most birds. Grosbeaks never eat the wings, which contain the greatest concentration of the toxins—so perhaps that’s part of how they limit their ingestion of toxins.
In most songbird species, only the male sings, as a way to attract a mate and to defend a territory. However, both males and female Black-headed Grosbeaks sing—and often, right from the nest. Both males and females will incubate the eggs, although only the female develops a full brood patch, a highly vascularized bare area of skin used to keep the eggs and featherless nestlings warm. Babies hatch after about 2 weeks and crawl out of their nests to perch in trees 10 – 14 days after hatching—a good 2 weeks before they can fly! The babies then sit very quietly on tree limbs and the parents keep track of whom to feed by remembering where the kids are. Both parents work to find food for the nestlings. Once the fledglings can fly, they again communicate constantly with their parents using a “whee-urr” call. If you have these grosbeaks in your area, you’ll hear these calls all through the daylight hours. Given that the babies spend so much time out of the nest before they can get around well, it’s amazing that lots of people don’t find baby Black-headed Grosbeaks dropping from the trees above them—a testament to skilled parenting and good-gripping baby feet!
Thanks to Wikimedia Commons for the two photos. You can see photos and hear a sample of their songs and calls here.