Each year, the Ohio Buckeye tree outside my porch window puts out a prodigious number of flower spikes, which reliably attract a few pollinators and one clever nectar thief.
Tennessee Warblers really have nothing to do with the state of Tennessee, but do migrate through there, where they were first seen and named way back in 1811. Like many small insectivores they spend the winter in the tropics, eating insects and nectar, and breed in the Canadian spruce forests where they specialize on spruce budworm and are critical to controlling outbreaks of the moth there.
Though they do visit flowers to consume nectar, they do not perform much of a pollination service for the plants, because they use their sharp beaks to pierce the flower at its base to get at the nectar at the bottom of the flower tube, thus avoiding the pollen on the anthers sticking far out of the flower.
The sugars in the nectar will be metabolized and stored as fat and should provide these tiny little birds (about 2/3 the size of a chickadee) with the fuel they need to get to the Canadian spruce forest to breed.
(these photos shot with the Sony RX10 iii bridge camera through my porch window — what an amazing little camera!)