"This warbler was difficult to photograph as it frantically hopped from branch to branch while foraging on a native gooseberry—one of the plants that flower in early spring in this part of Canada. Gooseberries are an important source of food for exhausted songbirds migrating north over the Great Lakes, and I was thrilled to get a clear image of this warbler drinking nectar from the tiny flowers.
Warblers are mainly insect eaters, but some also have a taste for nectar. On their main wintering grounds in Central America, Tennessee Warblers often show splashes of bright color on their faces, the result of probing in red or orange flowers. Their attraction to nectar continues as they migrate north. In the open woods of southeastern Canada and northern states, the inconspicuous blooms of eastern prickly gooseberry appear in late spring, just in time for migrating warblers to seek them out."