Cerulean Warbler Life History

Habitat

Cerulean Warblers breed in large tracts of older deciduous forests with tall trees. In the Appalachian Mountains many warblers nest on north and east-facing slopes and seem to gravitate toward gaps or openings in the canopy. They tend to use white oak, cucumber magnolia, bitternut hickory, and sugar maple for nesting and foraging, typically avoiding red oak and red maple. During migration, they forage and rest in primary and secondary tropical forests, shade coffee plantations, and scrub. On the wintering grounds they occur in evergreen forests, woodlands, and shade coffee plantations on the eastern slopes of the northern Andes from 1,600 to 6,500 feet.

Food

Cerulean Warblers are insectivorous, eating primarily insects such as flies, beetles, weevils, and caterpillars. In the winter, they also eat some plant material. They hop along branches in the canopy and pick insects from leaves and twigs.

Nesting

Nest Placement

Together male and female Cerulean Warblers choose the nesting location. They tend to pick white oaks, cucumber magnolias, and sugar maples. They place the nest on a branch in the canopy with clumps of leaves concealing the nest site from above. Nests are often placed near gaps in the canopy. Nest height varies considerably, from 16 feet to 115 feet above the ground.

Nest Description

Females weave together bark fibers, grass stems, and hair that they bind together with spiderwebs to form a cup-shaped nest. Males occasionally help collect spiderwebs at the beginning of nest construction.

Nesting Facts

Behavior

Cerulean Warblers hop along branches in the canopy searching for insects. In Arkansas and Tennessee researchers found that they tended to forage in the top third of the tree. Breeding pairs aggressively defend their canopy territories. Males sometimes attack each other, grappling with bills and feet as they tumble toward the ground. Pairs stay together for the breeding season, but their canopy lifestyle makes studying their nesting behavior challenging. On the wintering grounds, Cerulean Warblers occur in mixed-species canopy flocks primarily foraging with tropical tanager species.

Conservation

Cerulean Warblers are uncommon and their populations declined by an estimated 1.84% per year between 1966 and 2019 (amounting to a cumulative decline of 63% over that period), according to the North American Breeding Bird Survey. Partners in Flight estimates a global breeding population of 530,000 individuals. They rate the species a 15 out of 20 on the Continental Concern Score, placing the species on the Yellow Watch List for species with declining populations. The International Union for Conservation of Nature (IUCN) lists the species as Near Threatened. Cerulean Warblers were abundant throughout the Ohio and Mississippi River valleys during the nineteenth century, but they no longer breed throughout much of the area due to habitat loss. Loss and degradation of habitat on the breeding and wintering grounds appears to be the primary driver of population declines. Conservation efforts aimed at reversing these declines are focusing on forestry practices such as long rotation timber extraction and selective logging to create natural canopy gaps and uneven-aged forest stands.

Credits

Buehler, David A., Paul B. Hamel and Than Boves. (2013). Cerulean Warbler (Setophaga cerulea), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

Dunne, P. (2006). Pete Dunne's essential field guide companion. Houghton Mifflin Harcourt, New York, USA.

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

Partners in Flight. (2020). Avian Conservation Assessment Database, version 2020.

Pieplow, N. (2017). Peterson Field Guide to Bird Sounds of Eastern North America. Houghton Mifflin Harcourt Publishing Company, NY, USA.

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.

Sauer, J. R., W. A. Link, and J. E. Hines (2020). The North American Breeding Bird Survey, Analysis Results 1966–2019. U.S. Geological Survey data release.

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

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

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