Cerulean Warbler 2026

(C) Howard West

The Cerulean Warbler (Setophaga cerulea) is a small wood warbler (11.5 cm, 8–10 g) known for the male’s striking sky-blue breeding plumage. Males have blue backs with dark streaking, white underparts, two white wing bars, and a thin dark necklace. Females and young are bluish-green above, with a yellowish wash on their underparts and a faint whitish eyebrow. All cerulean warblers have two white wing bars in all plumages. They primarily breed in forests of the Appalachians, east to central Minnesota, south from southern Canada, and north to Tennessee. During the non-breeding season, they inhabit evergreen forests in the Andean Mountains from Colombia to Bolivia. Throughout their range, they rely on large expanses of high-quality forest habitat.

(C) Howard West

Cerulean warblers are specialized nesters. They forage, sing, and nest in the top third of deciduous trees, favoring large expanses of deciduous forest with mixed canopy openings on north- or east-facing slopes. In Pennsylvania, they have also been known to nest in riparian forests with large sycamore trees. Over the last couple of decades, their populations have declined by as much as 68%, and they are listed as a vulnerable species by the International Union for Conservation of Nature. In Pennsylvania, they are considered a species of high concern according to the State Wildlife Action Plan, with threats largely due to the loss of optimal habitat. Forest fragmentation leads to loss of optimal breeding habitat and decreased nest success. Conservation efforts commonly focus on increasing habitat quality by using long-rotation timber harvesting rather than aggressive logging, as well as selective logging to create natural canopy gaps in mature forests.

Cerulean warblers use all of Pennsylvania during the breeding season. They are most often seen along riparian trails and on deciduous forest slopes, high in the trees. Conserving optimal habitat in Pennsylvania is essential for the species, as the state lies within the core of their breeding range, and their nesting habitat continues to decline nationwide. (Karter Witmer)