Do rufous hummingbirds (Selasphorus rufus) use visual beacons?
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Animals are often assumed to use highly conspicuous features of a goal to head directly to that goal (‘beaconing’). In the field it is generally assumed that flowers serve as beacons to guide pollinators. Artificial hummingbird feeders are coloured red to serve a similar function. However, anecdotal reports suggest that hummingbirds return to feeder locations in the absence of the feeder (and thus the beacon). Here we test these reports for the first time in the field, using the natural territories of hummingbirds and manipulating flowers on a scale that is ecologically relevant to the birds. We compared the predictions from two distinct hypotheses as to how hummingbirds might use the visual features of rewards: the distant beacon hypothesis and the local cue hypothesis. In two field experiments, we found no evidence that rufous hummingbirds used a distant visual beacon to guide them to a rewarded location. In no case did birds abandon their approach to the goal location from a distance; rather they demonstrated remarkable accuracy of navigation by approaching to within about 70 cm of a rewarded flower’s original location. Proximity varied depending on the size of the training flower: birds flew closer to a previously rewarded location if it had been previously signalled with a small beacon. Additionally, when provided with a beacon at a new location, birds did not fly directly to the new beacon. Taken together, we believe these data demonstrate that these hummingbirds depend little on visual characteristics to beacon to rewarded locations, but rather that they encode surrounding landmarks in order to reach the goal and then use the visual features of the goal as confirmation that they have arrived at the correct location.
KeywordsBeacon Local cue Landmark Rufous hummingbirds
We thank the Natural Sciences and Engineering Research Council of Canada for funding SF and TAH and the Natural Environment Research Council (UK) for funding SDH. We thank David Shuker, Wolfgang Wiltschko and two anonymous reviewers for comments on an earlier version of the manuscript and Mark Klassen, Jono Henderson, Melissa Bateson, Erica Jeffery, Chelsea Matisz, Becci Dearnley, Melissa Groeneweg, Erika Droessler, Kim Urbaniak, Lucy Asher and Craig Barnett for their cooking and general field work support. These experiments comply with the laws of Canada and were conducted with the approval of the University of Lethbridge Animal Welfare Committee and under permits from Alberta Sustainable Research Development and Environment Canada.
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