Hummingbird foraging behavior in different patch types: simulation of alternative strategies
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The development of a model simulating alternative hummingbird foraging strategies is described and predictions of the model are compared with foraging patterns recorded in the field. The hypotheses that: (1) natural foraging patterns more closely resembled systematic foraging than random foraging; and (2) systematic foragers were more efficient when resource distributions were clumped versus random were tested. Simulated foraging strategies included random, area-restricted, and directional foraging. The random strategy randomly selected the flowers a hummingbird visited. The area-restricted strategy allowed a hummingbird to visit any flower directly adjacent to the current flower, with an equal probability of visiting any adjacent flower. The directional strategy was based on the previous and current flowers visited, with a hummingbird following a straight path until it encountered an edge. At an edge, the hummingbird had an equal probability of turning and moving in any direction. A three-flower memory was incorporated into the strategies, so a simulated hummingbird could not revisit the last three flowers visited. During field trials and simulations, hummingbirds foraged in patches of 36 artificial flowers with uniform, clumped, and random nectar distributions. All the flowers in a uniform patch contained nectar. A clumped patch consisted of clumps of four rewarding flowers interspersed with clumps of four empty flowers. A random patch contained randomly distributed rewarding and empty flowers. Foraging efficiency for the field foraging patterns was measured and foraging strategies were simulated as microliters of nectar consumed per time step, assuming higher rates of consumption were more efficient than lower rates of consumption. In random patches, the field foraging patterns were more efficient than the simulated foraging strategies, whereas the field foraging patterns and area-restricted strategy were the most efficient in clumped patches. In the uniform patch, the directional strategy was the most efficient, followed by the field foraging patterns and random strategy. The random strategy was more efficient in patches with random versus clumped nectar distributions, whereas the area-restricted strategy was more efficient in clumped patches. No differences existed between clumped and random patches for the directional strategy or field foraging patterns. These results suggested the hummingbirds used different foraging rules in different patch types and incorporated information not included in the simulated strategies into their foraging patterns. This approach of replicating field experiments with a spatially explicit simulation model provides a valuable methodology for evaluating the effectiveness of different foraging strategies under different patterns of resource availability. 2001 Elsevier Science B.V.
