Photo courtesy Charles Martinez
This week’s Bird of the Week, compliments of the Weminuche Audubon Society and Audubon Rockies, is the black-headed grosbeak.
This is another of our summer birds, celebrated for its long, sweet song. In addition to incorporating elements of the songs of American robins and western tanagers, this grosbeak’s song also weaves in whistles of its northern cardinal relative.
The beaks of black-headed and evening grosbeaks are similarly large and strong, causing them to share a common name, but these birds are not closely related. Instead, the black-headed grosbeak shares ties with members of the cardinal family, including indigo and lazuli buntings, blue and rose-breasted grosbeaks, western and summer tanagers, and northern cardinals.
For a male songbird, the benefits of song outweigh the danger of alerting predators to his presence. When longer hours of daylight in spring stimulate his hormones and induce him to sing, his song identifies his species to a potential mate and is his chance to show off his stamina and readiness to breed. It announces his territory to other males and alerts them to move on.
Displaying a trait unusual in temperate zone birds, female black-headed grosbeaks also sing, and both sexes sing from the nest. It is thought that by imitating a rival male in song, a female may keep her mate close to home where he is not likely to mate with another partner. Both sexes share incubation duties and feeding of the young.
Breeding males are colored cinnamon-orange and have black heads and black and white wings. Females and immature males are streaked brown and white on the back and orange on the breast. Their heads are striped.
Strong beaks allow these birds a varied diet that includes heavy walled seeds; large, hard-bodied insects like beetles; snails; fruits including those in orchards; and berries. When they’re not on the nest, they readily come to sunflower seed feeders. Where their winter habitats in central Mexico overlap those of monarch butterflies, toxic to most birds, these grosbeaks are one of their few predators.
Phone apps like Merlin, developed by Cornell Lab, which link bird species to recordings of their songs, have become popular tools in learning to identify birds by their songs.
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