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Grace's Warbler Life History

Habitat

Habitat Forests

Over its large range, the Grace’s Warbler nests and winters mostly in mature pine and pine-oak forests in mountainous regions. Near the southern limit of its range, it breeds in lowland savannas of Caribbean pine (Belize); whereas in the northern extreme, it ranges into Engelmann spruce–white fir forests. In Arizona and New Mexico, Grace’s Warbler favors ponderosa, Chihuahua, pinyon, Apache, and southwestern white pine forests, which often have understories of Gambel’s, Emory, Arizona white, or silverleaf oaks, alligator juniper, mountain mahogany, Utah serviceberry, and snowberry. In Mexico, similar habitats are dominated by Aztec, Cooper’s, Montezuma, Mexican yellow, and smooth-bark Mexican pines, red, white, and netleaf oaks, madrone, and manzanita. Migrants and wintering birds use habitats very similar to breeding habitats. Grace’s Warblers seldom occur in deserts or other lower-elevation habitats in the western U.S.

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Food

Food Insects

Grace’s Warblers eat insects (beetles, flies, dragonflies, caterpillars) and spiders, which they catch while foraging nimbly in the upper third of mature pine trees, well away from the trunk, along smaller branches, twigs, and in pine-needle clusters. They forage to a lesser extent in oak trees when they're available. They occasionally catch flying insects on the wing or feed on the ground. Unlike the related Yellow-throated Warbler of the eastern U.S., Grace’s does not forage along large limbs or on the trunk.

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Nesting

Nest Tree

The female selects the nest site, usually inside a pine needle cluster near the outer edge of the tree, typically more than 30 feet above the ground.

Nest Description

The female builds a flat cup of plant fibers, wool, animal hair, and string, lining it with feathers, fine grasses, rootlets, and hair, bound together with spiderweb. Nests average about 2.7 inches across and 2.2 inches tall, with interior cup 1.8 inches across and 1.3 inches deep.

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Behavior

Behavior Foliage Gleaner

Soon after they return to nesting areas, male Grace’s Warblers begin singing to advertise to females and to mark their rather large territories. Males sing and follow females for several weeks before the pair begins building a nest, a rather long period compared to most warblers. The female selects the nest site and builds the nest, as in most warbler species. Males chip loudly and chase away rival males, especially before the female lays eggs. Both male and female help incubate the eggs and rear the young. After the young fledge, family groups forage together, mixing with other warblers and with woodland birds such as Mexican Chickadees and Bridled Titmice.

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Conservation

Conservation Declining

According to the North American Breeding Bird Survey, Grace's Warbler populations declined by an estimated 1.5% per year between 1968 and 2015, resulting in a cumulative decline of 52% over that period. Partners in Flight estimates a global breeding population of 3 million, with about 1.7 million of those breeding in the United States. Partners in Flight rates the species a 14 out of 20 on the Continental Concern Score, and includes Grace's Warbler on the Yellow Watch List for species in decline. The decline of Grace’s Warbler is due in part to the loss of mature pine forests in the U.S. and Mexico, fire suppression, logging, and other forestry practices that favor smaller trees and different forest structure.

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Credits

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

Sauer, J. R., D. K. Niven, J. E. Hines, D. J. Ziolkowski Jr., K. L. Pardieck, J. E. Fallon, and W. A. Link (2017). The North American Breeding Bird Survey, Results and Analysis 1966–2015. Version 2.07.2017. USGS Patuxent Wildlife Research Center, Laurel, MD, USA.

Sibley, D. A. (2014). The Sibley Guide to Birds, second edition. Alfred A. Knopf, New York, NY, USA.

Stacier, Cynthia A. and Michael J. Guzy. (2002). Grace's Warbler (Setophaga graciae), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

Stephenson, T. and S. Whittle (2013). The Warbler Guide. Princeton University Press, New Jersey, USA.

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