Northern Oriole

The birds formerly known as the "Baltimore Oriole" in the east and "Bullock's Oriole" in the west were once thought to be separate species. However, when trees were planted in the Great Plains it was found that the two birds interbreed and most birds of that area have indeed become hybrids. In Lord Baltimore colors, it is one of the brightest local birds and has a voice to match its distinctive plumage.

In the east the male has bright orange breast, rump and shoulder patches while the head, back, and wings are black. Females are duller olive brown with dull orange-yellow underparts and two white wing bars. The western male is similar to the eastern male but also orange cheeks and eyebrows and a large white wing patch. The western female is whitish underneath.

The males arrive in early May, trumpeting their rich, mellow notes loud, clear and far-reaching, one of the reassuring notes of the season. The song is a rather disjointed composition of whistled two-note phrases and shorter, softer single notes broken by long pauses. It tends to be quite variable but of the same general quality and tone. Each male has a recognizably different song.

Source: http://www.wikipedia.org/