Arthropod Foraging by a Southeastern Arizona Hummingbird Guild

We tested the hypothesis that foraging for arthropods may be a viable source of energy when hummingbirds are competitively excluded from sources of nectar. We hypothesized that the Magnificent Hummingbird (Eugenes fulgens) relies more upon arthropods than the Blue-throated Hummingbird (Lampornis clemenciae) or Black-chinned Hummingbird (Archilochus alexandri) in southeastern Arizona. We were unable to quantify arthropod foraging by A. alexandri, but measured frequent arthropod foraging by both E. fulgens and L. clemenciae. E. fulgens engaged in more aerial flycatching than L. clemenciae, and their rate of flycatching attempts was higher than by L. clemenciae. Analysis of gut contents showed that E. fulgens consumes the greatest diversity of arthropods. Respiratory quotient measurements indicated E. fulgens catabolized a greater amount of fat/protein than the other species. Gut morphology of E. fulgens does not appear to differ from other hummingbirds suggesting hummingbirds in general may have the ability to use arthropods as an alternative energy source when access to floral energy is restricted. Our data are consistent with the hypothesis that the diet of E. fulgens includes more arthropods than other species with which they compete.Donald R. Powers, Jessamyn A. Van Hook, Elizabeth A. Sandlin and Todd J. McWhorte