Black-headed Grosbeak Life History

Habitat

Habitat ForestsBlack-headed Grosbeaks breed in complex habitats with a diversity of plants and ready access to water. They avoid monotonous stretches of unbroken dry chaparral, desert, grassland, or dense coniferous forests, but inhabit edges where those habitats are disturbed or meet others. A combination of large trees and rich understory seems ideal, whether found in groves of cottonwood or aspen on floodplains or stream margins, in broken pine forests or deciduous canyons and valleys, or in gardens, orchards, and suburban developments. Grosbeaks choose winter habitats in subtropical and tropical lowlands in Mexico with similar features. During migration they tend to seek out shrubs and trees rich in berries.Back to top

Food

Food InsectsBlack-headed Grosbeaks' massive bills make them well equipped for cracking seeds, but those beaks are just as useful for snatching and crushing hard-bodied insects or snails. Insects (especially beetles), spiders, and other animals make up about 60% of their breeding-season food. Fruits and seeds make up most of the rest. Berries are a favored food during migration. Among wild fruit, juneberries, poison oak, and elderberries make common meals. Other regular foods include grains like oats and wheat, and weed seeds such as dock, pigweed, chickweed, and bur clover. They also feed on cultivated orchard fruit like figs, mulberries, cherries, apricots, plums, blackberries, and crabapples. In spring and summer, they feed at sunflower seed feeders and at nectar feeders set out for orioles. Where their range overlaps with wintering monarch butterflies, grosbeaks eat large numbers of these insects. Black-headed Grosbeaks don’t seem to suffer from the toxins concentrated in the monarchs’ bodies, which render them inedible to most birds.Back to top

Nesting

Nest Placement

Nest TreeNests are typically placed in the outer branches of a small deciduous tree or bush near a stream, up to about 25 feet high. They are generally well concealed by leaves and branches. Spots may be chosen to make nest cooling easy.

Nest Description

The female builds a bulky, loosely constructed nest that’s about 5–7 inches across and 2–4 inches deep. She uses slim twigs, stems, rootlets, and pine needles with no mud or cementing. She lines the 3–4 inch wide inner cup with finer stems, rootlets, hair, string, and green material, making a 1–2 inch deep hollow. It usually takes her 3 to 4 days to build the nest, gathering most of the material in the first days and intensifying assembly later on. The loose construction (sometimes so loose that the eggs can be seen through the bottom) may help provide ventilation to keep nest and eggs cool.

Nesting Facts
Clutch Size:2-5 eggs
Number of Broods:1 brood
Egg Length:0.9-1.1 in (2.3-2.7 cm)
Egg Width:0.7-0.8 in (1.7-1.9 cm)
Incubation Period:12-14 days
Nestling Period:10-14 days
Egg Description:Pale to greenish blue with brown or reddish brown spotting.
Condition at Hatching:Helpless, nearly naked, with eyes closed; sparse grayish white down on apricot skin.
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Behavior

Behavior Foliage GleanerBlack-headed Grosbeaks glean most of their food in the treetops and understory, less frequently lunging at prey, and occasionally snatching flying prey from the air. They hop on branches or at feeders, cracking seeds and hard-bodied insects with their heavy bills. After spring migration, tight-knit pairs form quickly. Males court females with vigorous singing and striking displays called "nuptial flights" lasting 8 to 10 seconds: the male flutters up from a perch, singing and spreading his wings and tail to reveal the bold white-on-black patterns, rising several feet before settling back on the same perch. Singing helps with territorial defense, although both males and females will attack other grosbeaks that intrude. Aerial grappling attacks can be ferocious. They tend to tolerate species such as warblers and Bushtits that come near the nest, but they attack predators including Western Scrub-Jays and Steller’s Jays. Both males and females sing on the nest, and they share the chick-rearing duties of sitting on the eggs and feeding the young about equally. Black-headed Grosbeaks may form loose flocks during fall migration and winter.Back to top

Conservation

Conservation Low ConcernBlack-headed Grosbeak populations are stable or increasing throughout their range, according to the North American Breeding Bird Survey conducted between 1966 and 2014. Partners in Flight estimates the global breeding population at 14 million, with 4% breeding in Canada, 75% spending some part of the year in the U.S., and 100% in Mexico. They rate a 9 out of 20 on the Continental Concern Score and are not on the 2014 State of the Birds Watch List. While urbanization has destroyed some prime habitats, the grosbeaks' adaptability has served them well. They aren't particularly fussy about breeding habitat or nest materials, nesting in many species of trees and shrubs. Nor are they fussy eaters, mixing a wide variety of animal and plant foods. They inhabit disturbed landscapes like irrigated field edges, second-growth forests, orchards, and suburban greenbelts, though they keep their distance from intensive human activity. In some areas, Scrub and Steller's jays are significant nest predators, but grosbeaks seem relatively resistant to brood parasitism by the Brown-headed Cowbirds that trouble other birds in their range.Back to top

Backyard Tips

Attract Black-headed Grosbeaks by setting out sunflower seed feeders, and don't be surprised to find them at nectar feeders set out for orioles. They'll even nest in backyards and gardens where enough cover is available and water is nearby.

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Credits

Lutmerding, J. A. and A. S. Love. Longevity records of North American birds. Version 2015.2. Patuxent Wildlife Research Center, Bird Banding Laboratory 2015.

North American Bird Conservation Initiative. 2014. The State of the Birds 2014 Report. US Department of Interior, Washington, DC, USA.

Ortega, Catherine and Geoffrey E. Hill. 2010. Black-headed Grosbeak (Pheucticus melanocephalus), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

Partners in Flight (2017). Avian Conservation Assessment Database. 2017.

Sauer, J. R., J. E. Hines, J. E. Fallon, K. L. Pardieck, Jr. Ziolkowski, D. J. and W. A. Link. The North American Breeding Bird Survey, results and analysis 1966-2013 (Version 1.30.15). USGS Patuxtent Wildlife Research Center 2014b. Available from http://www.mbr-pwrc.usgs.gov/bbs/.

Sibley, D. A. (2014). The Sibley guide to birds, second edition. Alfred A. Knopf, New York, USA.

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