Spatial and temporal patterns of resource heterogeneity and foraging behavior

Abstract

Movement patterns reflect how an animal responds to aphics. variations in resource distribution, with important implications for management and conservation concerns. Foraging paths and food items provide a unique opportunity to relate movement to target resources. I studied Black-chinned (Archilochus alexandri) and Buff-bellied Hummingbirds (Amazilia yucatanensis) foraging at Turk's Cap (Malvaviscus arboreus var. drummondii) and artificial flowers in southern Texas. l quantified the distribution of nectar resources, recorded hummingbird foraging patterns in relation to nectar distributions and used patches of artificial flowers to experimentally study hummingbird foraging behavior. Nectarivore activity increased the number of M. arboreus flowers with little or no nectar and decreased the number of flowers with large amounts of nectar. With nectarivore visitation, age 1 flowers contained the greatest number of milligrams of sugar in the afternoon and the lowest in the morning. Without nectarivore visitation, the milligrams of sugar in age 1 flowers increased continuously throughout the day. Meal size correlated significantly with nectar availability for all species and sexes. A. alexandri consumed significantly more milligrams of sugar per foraging bout than A. yucatanensis, suggesting they used different foraging strategies. Female A. alexandri did not consume significantly larger meals than males, suggesting similar energetic constraints. For the artificial flower experiments, 1 evaluated foraging efficiency in terms of consumption rates, assuming higher consumption rates were more efficient than lower consumption rates. Foraging efficiency did not vary between clumped and random resource distributions for any of the species or sexes. Only male A. alexandri visited significantly more high and low quality artificial flowers than empty ones, while none of the species or sexes visited more high than low quality artificial flowers. Therefore, none of the study animals appeared to learn the location of fixed, rewarding clumps. A. alexandri females and A. yucatanensis consumed significantly more []/sec during stochastic trials than during fixed trials. A. alexandri females and A. yucatanensis visited significantly more red, low quality artificial flowers than green, high quality or empty artificial flowers. However, A. alexandri females foraged significantly more efficiently with color cues when low and high quality flowers were considered equal in value.