The yellow-rumped warbler is nicknamed “butter butt.” Rude? Nah. That moniker would be kind of a dig for a person, but it’s affectionate—and apt—for this common, brightly-coloured bird. Males not only have yellow butts, they also have stark yellow patches on the tops of their heads, in front of their wings, and above the base of their tails. As with some other flashy species, their colours start to fade by the fall.
Butter butts—er, yellow-rumped warblers—are hyperactive bug-eaters, often flitting about. But unlike many other warblers, yellow rumps are gregarious. They forage in groups, keeping to lower branches in plain sight instead of skulking in thick undergrowth. This makes the yellow-rumped warbler an easy one to tick off your birding bucket list. Win!
Yellow-rumped warblers also tend to spend more time in cottage country than any other member of their family. They’re generalists, and can survive on berries, seeds, and even tree sap for long stretches of time. Consequently, some arrive as early as April, and stay as late as mid-October.
The yellow-rumped warbler migrates at night. There’s less air turbulence, and it’s cooler. Just like other migrant birds that travel at night, yellow rumps seem to orient themselves towards the North Star. If it’s very cloudy or rainy, they land and wait for clear conditions to hit the road again. Stopping gives them a chance to rest, and a precious opportunity to eat (insects, mostly) so they can rebuild their depleted fat stores. Migrating takes a lot out of a little bird—some warblers lose as much as 50 per cent of their body weight during the fall journey.