The bird itself has become harder to observe in recent decades, as its numbers have decreased in parts of its range. The sky-blue upperparts of the male Cerulean Warbler are difficult to observe in summer: At that season, the birds stay high in the tops of leafy trees in the eastern United States and extreme southern Canada. These long-distance migrants breed in mature eastern deciduous forests and spend the winters in … They are found in deciduous forests of eastern North America during the breeding season and the Females and immature birds have greyer or greenish upperparts, a pale stripe over the eye, and no streaking on the back and no neck. Females are equally well-dressed, wearing a dusky hue of blue-green. All of these birds have wing bars and a thin pointed bill. Cerulean Warbler. That’s the male Cerulean Warbler, a brilliant blue songbird with a cerulean neck band and streaks down the sides. Setophaga cerulea. Adult males have pale cerulean blue and white upperparts with a black necklace across the breast and black streaks on the back and flanks. The cerulean warbler’s summer range extends eastward from the Great Plains in eastern North and South Dakota, Nebraska, Kansas, and Oklahoma; south to Arkansas, Mississippi, Tennessee, northern Alabama and Georgia, and South Carolina; north to Massachusetts, southern Quebec, southeastern Ontario, Michigan, Wisconsin, and central Minnesota. The cerulean warbler is a small songbird of the New World warbler family.