Hummingbirds modify their routes to avoid a poor location

Maria C Tello-Ramos,Mabel Barclay,T Andrew Hurly,Susan D Healy

doi:10.3758/s13420-021-00476-3

Maria C Tello-Ramos, Mabel Barclay + Show 2 more

Open Access

https://doi.org/10.3758/s13420-021-00476-3

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Abstract

Traplining, when animals repeat the order in which they visit a number of locations, is taxonomically widespread, but little is known about which factors influence the routes that animals follow. For example, as the quality of rewarding locations changes over time, foragers are expected to update their traplines, either to prioritize locations where the reward increases or to avoid locations that have ceased to be profitable. Here, we tested how traplining wild hummingbirds responded to increases or to decreases in the sucrose concentration of one of the flowers on their trapline. Hummingbirds did not change their trapline to visit the flower with the increased reward first, but by changing the order in which they visited flowers, they avoided a flower that contained a decreased reward. Depending on where along the trapline the reduced-content flower occurred, hummingbirds either changed the origin of their trapline or changed the direction in which they flew around their trapline. It may be that this asymmetric modification of foraging traplines is especially noticeable in risk-averse foragers, such as these territorial hummingbirds.

Highlights

Traplining, when animals repeat the order in which they visit a number of locations, is taxonomically widespread, but little is known about which factors influence the routes that animals follow
The task of estimating the shortest route connecting several locations is analogous to the travelling salesperson problem (TSP), where an individual has to find the optimal route around several locations before returning to the starting point (Schrijver, 2005)
Regardless of the complexity of this task, a wide range of animals typically arrive at the shortest route connecting several locations

Summary

Introduction

Traplining, when animals repeat the order in which they visit a number of locations, is taxonomically widespread, but little is known about which factors influence the routes that animals follow. When resources are constant in space and time, desert ants (Cataglyphis fortis) take direct paths from the nest to a known resource by using path integration (Collett et al, 1999), while displaced honeybees combine path integration information and the location of landmarks to make shortcuts when homing or travelling to a feeder (Menzel et al, 2005) How animals update their routes between multiple locations when the resources change is less well understood. When one of the flowers suddenly contained a higher reward, the bees prioritized visiting this location, even though the new route was no longer the shortest (Lihoreau et al, 2011) This scenario is relevant to centralplace foragers that feed from a resource that is stable in space but that varies with time. Nectar provided by flowers is such a resource, and so we might expect to observe similar development of, and changes to, traplines in other nectarivores

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