Foraging behavior of Archilochus colubris (Linnaeus).

Abstract

The high-energy demands of the Ruby-throated hummingbird (Archilochus colubris) require them to feed frequently. This makes them excellent organisms for studying foraging behaviors of birds. It has been shown that hummingbirds show some feeding preferences. Stiles (1976) suggested that they rank food in the following order: (1) energy content, (2) taste, (3) color. He also found that when offered glucose, sucrose, and fructose, hummingbirds would least prefer fructose, which has a bitter aftertaste. Our experiment was constructed to determine if the Ruby-throat would exhibit a preference based on taste by offering sweet, sour, and bitter solutions with equal sucrose concentrations. Our results showed that they signficantly preferred the sweet to the bitter and sour solutions. We further explored taste preferences by elevating the sucrose in the bitter and sour solutions, but keeping the sweet solution at the original level. The hummingbirds significantly preferred the elevated bitter solution to the sweet and elevated sour solutions. Our results demonstrate that hummingbirds can differentiate between tastes while using energy content as a proximate cue for foraging. Our last experiment explored optimal foraging by providing a choice of feeders with and without perches, but containing identical sucrose solutions. Although the distribution of visits to the two feeders was not significantly different, the mean numbers of dips and mean duration of visits were significantly greater for the feeder with the perch. Our results demonstrated that once hummingbirds were at the perched feeder, they optimized their foraging efficiency.