About The Cerulean Warbler
Sky Blue, White, and Dark Streaks
Cerulean Warbler Characteristics
The Cerulean Warbler is around 4 inches long and weighs between 8-10 grams. They weigh about the same as two nickels and are about the size of a ping pong ball.
The male cerulean has a sky-blue color from the top of its head to its back, with white wingbars, and black stripes on the wings and tail. Males will also have white underneath and a dark-blue “necklace.”
The female cerulean has an aqua or seafoamgreen color with yellow underneath. Females will also have a white supercilium stripe – which is a pale white stripe from the beak to the eye.
Easiest to detect in spring and summer by its loud buzzy song, similar to Black-throated Blue Warbler but usually richer and more distinctly three-parted; much lower-pitched than Blackburnian Warbler.
Forests, Fire, and Ridgelines
Cerulean Warbler Habitat Needs
Across the state, the Cerulean Warbler prefers large blocks of mature, deciduous forest. However, they appear to key in on disturbance within these large forest blocks for nesting. Historically, these disturbances, or breaks in the canopy, were likely caused by insect outbreaks, wind storms, and other natural events. Perhaps most notably, fire likely played an important role in creating and maintaining these patchy openings as well.
Ceruleans also seem to key in on topographic features when choosing nest sites. Ridgelines are often chosen in Indiana, which is consistent with nest locations from other states (Weakland and Wood 2005). Tree species also seem to matter, and white oak, chestnut oak, and several species of hickories are common components of breeding habitat. The largest trees (>16 inches in diameter) are often chosen as nest locations (Wood, P.B. et al, 2013).
Declining, State-Endangered, and Habitat Loss
Cerulean Warbler Conservation Status
The Cerulean Warbler has lost around 70% of its global population and it has been significantly declining since the 1970’s – one of the fastest declining migratory songbirds in the United States.
Currently, the Cerulean Warbler’s population size sits at 530,000. The American Bird Conservancy has listed the Cerulean Warbler as Near Threatened. This category means that the Cerulean Warbler has a risk of becoming endangered in the future. In Indiana, the Cerulean Warbler is listed as State-Endangered.
There are many reasons for the decline in Cerulean Warbler populations. In North America, there is less desirable breeding habitat due to the lack of disturbance in forest canopies, forest fragmentation, and forest structure changes with beech-maple forests dominating oak/hickory forests.