One of the reasons why flowering plants became the most diverse group of land plants is their ability to associate with animals to enhance their reproduction. Some of the earliest examples of this mutualism involved insects looking for food in plants and inadvertently pollinating them. Vertebrates are latecomers to these mutualisms, but birds present many nectar-feeding clades and repeated convergent evolution of bird-pollinated plants is also striking both in traits and diversity. One particular set of convergences both among these birds and plants has long attracted the attention of researchers: the match between the shape/size of bills and flowers. Traditional explanations for the coevolution of bill-flower matching include that bird-pollinated plants evolved traits, such as long and thin corollas, to prevent specific visitors (e.g. insects) from accessing the nectar, and that increased matching benefits both the bird (nectar extraction efficiency) and the plant (pollen transfer). Focusing on a highly-specialized group, hummingbirds, I present a workflow to examine the expected benefits from the bill-flower matching. This theoretical and methodological framework includes experiments under controlled conditions with captive birds (e.g. variable nectar access and properties), in semi-controlled conditions with free-living ones (e.g. PIT-tagged hummingbirds), and ways to quantify performance during actual floral visits (e.g. high-speed videography) in the wild. I propose to link inferences from experiments and natural behaviors to validate emerging models of nectar extraction and hummingbird energetics. Additionally, I discuss evolutionary forces, other than nectar-feeding, on the evolution of hummingbird bills and foraging behavior, that may influence their performance and behavioral strategies, ultimately shaping the interactions with competitors and the plants they pollinate/feed from.