Yellow-rumped warblers, also known as “butter butts” or “myrtle warblers,” are small songbirds found throughout North America. Here are some fascinating facts about these colorful little birds:
Identification
Yellow-rumped warblers are relatively small, measuring 4.7-5.5 inches in length and weighing just 0.3-0.5 ounces. Their most distinctive feature is the yellow rump patch, from which they get their name. Males have blue-gray heads, backs, and wings, with black streaks on the back and white bellies. Females are duller, with brown streaking on the back and flanks. Both sexes have a bold white patch on the wings and tail.
Range and Habitat
Yellow-rumped warblers breed in forests across Canada and the northern United States. Their breeding range extends from Alaska across to Newfoundland and south along the East Coast to North Carolina. On the West Coast, they breed down to California. They migrate in the winter down to Mexico and across to Florida, the Gulf Coast, and the Caribbean. These birds can be found in a variety of forest habitats including both coniferous and deciduous woodlands.
Diet
Yellow-rumped warblers have a diverse diet consisting of insects and other invertebrates as well as fruits and seeds. Some of their favorite foods include:
- Spiders
- Caterpillars
- Beetles
- Ants
- Flies
- Bees
- Berry seeds
- Wax myrtle berries
- Bayberry fruits
- Poison ivy fruits
Their ability to digest wax myrtle and bayberry fruits allows them to winter farther north than many other warbler species. They are sometimes called the “butter butt” warbler because of the yellow globs of bayberry wax that collect on their rumps as they eat these waxy fruits.
Migration
Yellow-rumped warblers are champion migrants, making the round trip of up to 8,000 miles from their breeding grounds to their wintering grounds every year. They migrate mostly at night and can fly 200-300 miles in a single night during migration periods. Some key facts about their migration include:
- They are one of the first warblers to appear in spring and the last to leave in fall.
- They migrate through the Appalachians and across islands in the Caribbean.
- Many winter along the U.S. Gulf Coast and in Mexico.
- Males arrive early on the breeding grounds to claim the best territories.
Nesting
Yellow-rumped warblers build cup-shaped nests in the fork of a tree. The female lays 3-6 eggs and incubates them for 11-13 days. After hatching, both parents feed the nestlings for another 9-12 days until they fledge. Other nesting facts include:
- Nests are made of twigs, bark, moss, spiderwebs, and lined with feathers.
- Females build a new nest each year, usually 5-60 feet above ground.
- Some females lay eggs in another female’s nest in a practice called brood parasitism.
- Cowbirds sometimes lay eggs in yellow-rumped warbler nests.
Conservation Status
With a large population estimated between 32-72 million, yellow-rumped warblers are considered one of the most abundant warblers in North America. They are classified as a species of Least Concern on the IUCN Red List. Population numbers appear to be stable or even increasing in some areas.
Fun Facts
- Their scientific name Setophaga coronata means “crowned moth-eater.”
- They forage by hovering to pick insects from leaves and branches.
- They are one of the top distributors of myrtle seeds across their habitat.
- Their song is a series of whistled “sweet swee swee” phrases.
- They can survive cold temperatures by lowering their body temperature and entering short-term torpor.
Importance to Ecosystems
As abundant insect-eaters, yellow-rumped warblers help control insect pest populations in forests across North America. They also play an important role in seed dispersal and pollination for plants like wax myrtles, bayberries, and poison ivy. The fruits from these plants provide critical winter food sources when insects are scarce. Their partnerships with these plants exemplify an important interdependent relationship in their forest ecosystems.
Comparisons with Other Birds
Yellow-rumped warblers overlap in range with some similar looking warbler species. Here’s how to tell them apart:
- Pine warbler – Lacks yellow rump patch, yellow on throat and breast
- Prairie warbler – Olive-gray upperparts with black streaks, yellow underparts with black streaks
- Palm warbler – Yellow underparts with brown streaking, constantly pumps tail
- Yellow warbler – Entirely yellow underparts, no white wing bars
Where to Spot Yellow-rumped Warblers
Here are some top places to spot yellow-rumped warblers throughout the year:
- Breeding grounds – Northern forests like the Boreal forest, Adirondacks, and Appalachian Mountains
- Migration stopovers – Coastlines along the Great Lakes, Atlantic Ocean, Gulf of Mexico, and Caribbean islands
- Winter grounds – Southern coastal states, Mexico, Bahamas, and Cuba
- Backyards – These birds readily visit bird feeders, especially ones stocked with suet
Conclusion
With their vibrant plumage, energetic flight, and cheerful song, yellow-rumped warblers add beauty and activity to forests and backyards across North America. Learning about their migration routes, preferred foods, nesting habits, and role in plant pollination gives us a deeper appreciation for these hardy little birds. The abundance and adaptability of the yellow-rumped warbler shows the success of an avian underdog able to thrive among much rarer and more colorful wood-warbler species.