The yellow-rumped warbler is a mid-sized warbler found in North and Central America. They get their name from the bright yellow rump patch that is located at the base of the tail. This patch has also the reason for their nickname, "Butter Butt". They also have yellow on their heads and yellow patches on their sides. Males are usually a striking contrast of black and white, while females tend to be more brown.
Yellow-rumps are expert foragers. They primarily eat insects which they glean from trees, males typically foraging higher in the trees then females. They will also catch insects on the wing, flying out from the branches that they have been gleaning from like a flycatcher. When there are no insects around yellow-rums will eat seeds and berries. They are the only species of warbler that can digest bayberries and wax myrtles. Because of this they are able to winter further north then other warbler species. Which is why they are usually the first warbler species that we see in spring and the last to leave in the fall.
There are four different variations of yellow-rumped warblers. Two of the forms are non-migratory. They are the Black-fronted, from north western Mexico, and the Goldman's from Guatemala. The other two forms are migratory. They are the Myrtle (top 2 photos), which breed in eastern Canada and parts of the northern United States, and the Audubon (last photo) Which breed in western Canada, Alaska, the Pacific Coast, and Rocky Mountains. Both forms winter in the southern United States, Mexico, Central America and the Caribbean.