It is hard to identify a female or juvenile warbler that has very different plumage from a male of the same species by scrolling through a list of warbler photographs. I finally had my eureka moment when I Googled “yellow and black tail feathers”.
This feathered creature was actively hopping from branch to branch, in a pretty Cutleaf Weeping Birch, probably startling some insect snacks by spreading its tail and quickly flashing the yellow feathers. Where the female and juvenile birds have grey and yellow feathers, the breeding males have pitch black and bright orange feathers.
Oo, it has whiskers. It turns out they are specialized feathers called rictal bristles. They are common in insectivorous birds. They help protect the bird’s eyes from objects hitting them when the bird is in flight. The experiment did not sound fun for the birds.
“Particles released in front of the bird’s open mouth and blown back towards its head struck an eye more frequently after the rictal bristles had been removed.” (M. Conover and D. Miller, 1980)
Setophaga ruticilla means moth-eating redtail (based on breeding male tail colour).