Cerulean Warbler
Dendroica cerulea
The Cerulean warbler is a small, sky-blue bird most often seen flitting around the upper canopy of mature deciduous eastern forests. As with most warblers, males and females look quite different from each other. Male cerulean warblers are bright blue above and white below. They have black streaks on their sides and back, two white wing bars and a black line, or “necklace”, across their front. Females are dull turquoise above with a pale blue crown and yellowish-white below. They also have white wing bars but do not have the necklace or streaking that males do.
Size 4 inches
Wingspan 8 inches
Weight 0.28 – 0.35 ounces
Diet
Staple Insects
Population
The cerulean warbler’s population is dropping faster than any other warbler species in the United States. Between 1966 and 1999, it declined an average of 4% per year throughout its eastern US breeding range for a total population loss of 70%. Current estimates are at around 560,000 birds.
Range
Breeding Range Southeastern North America from the lower Great Lakes
region, southern Quebec and New England down to northern Louisiana and
northwestern Georgia. It is especially prevalent in southern Missouri and
Wisconsin, eastern Kentucky, eastern Ohio and West Virginia.
Winter Range The
cerulean warbler spends most of the year in northern South America from northern
Columbia and Venezuela down to southern Peru and northwestern Bolivia.
Behavior
Song Only the male warbler sings and his vocalization is quite distinctive – rapid buzz-like notes on one pitch followed by a short series of rising and accelerating notes, ending with a high buzz-like trill. ZHEE ZHEE ZIZIZIZI zzzzeeet.
Migration They are nocturnal migrants and usually arrive in their breeding range in late April or early May. They leave in August and migrate to forested mountain regions of western South America, where they can often be found feeding with flocks of local birds like the tropical tanager.
Reproduction
Mating Season April to May
Clutch size 3-4 eggs
They usually have only one brood per breeding season. The eggs are gray to
greenish white with brown specks. When they hatch, both parents feed the
young.
Nest The nest is made of grass, bark fragments and hair. These are all bound together with a spider web. If the female has to abandon a nest and begin a new one, she will leave behind the grass, bark and hair, but will take the spider web with her for the new nest.
Threats
Habitat destruction due to agriculture and development is a major threat. Habitat fragmentation also causes egg parasitism by brown-headed cowbirds: When cerulean warblers have nests on the edge of a fragmented area, brown headed cowbirds lay their eggs in warblers’ nest (as well as in those of other species). The cowbird eggs hatch before cerulean warbler eggs and the young cowbird will often push the unhatched warbler eggs out of the nest. The adult cerulean warblers cannot tell the difference between the brown-headed cowbird and their own young, so they raise them as their own.
Legal Status/Protection
The cerulean warbler is protected under the Migratory Bird Treaty Act*. In October 2000, 28 conservation organizations, including Defenders of Wildlife, petitioned the US Fish and Wildlife Service to list this species as threatened under the Endangered Species Act*. To date, the Service has not taken any action.
*The Migratory Bird Treaty Act implements various treaties and conventions between the U.S. and Canada, Japan, Mexico and the former Soviet Union for the protection of migratory birds. Under the Act, taking, killing or possessing migratory birds is unlawful.
**The Endangered Species Act requires the US federal government to identify species threatened with extinction, identify habitat they need to survive, and help protect both. In doing so, the Act works to ensure the basic health of our natural ecosystems and protect the legacy of conservation we leave to our children and grandchildren.
How You Can Help
- Help Cerulean Warblers and other wildlife by adopting an animal at our Wildlife Adoption Center.
- Take Action for Wildlife at our Wildlife Action Center.
For additional information
Visit Defenders' Imperiled Species: Cerulean Warbler pages for more information about what Defenders is doing to help.
Cornell Lab of Ornithology
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