Do rufous hummingbirds (Selasphorus rufus) use visual beacons?

Abstract

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.

Noise pollution alters ecological services: enhanced pollination and disrupted seed dispersal

“…Artificial flowers are frequently used in pollination studies [21,22] and those used in our experiment were constructed from 0.6 ml microcentrifuge tubes. This microcentrifuge tube size had been used previously in pollination experiments with A. alexandri [23].…”

Wild hummingbirds can use the geometry of a flower array

“…While some birds (i.e., 4 of 10) did do this, the group of birds as a whole were no more likely to choose the flower closest to the red landmark than they were to choose any of the other flowers. Although we should be cautious in our interpretation given the small sample size, we think it more likely that the landmark may have scaffolded the learning of the reward's location as seen in previous tests of landmark use in this species (Hurly et al 2010), but it was not sufficient to control the birds' test choice after the rotation and translocation of the array.…”

“…They will also encode views of the panorama surrounding the flower (Pritchard et al 2015(Pritchard et al , 2016 and perhaps local, natural landmarks (e.g., small bushes, ground squirrel holes; Nardi et al 2015, Hurly et al 2010). Now we can add geometric cues provided by the relationship among the four flowers to this list.…”

What hummingbirds can tell us about cognition in the wild

“…We trained birds to fly to a rewarded flower (a red 8cm 3 cardboard cube) in a large featureless field, then removed the flower and filmed the bird's flight path into the location of the now-missing flower. The birds flew to within 60cm in the horizontal plane and within 20cm in the vertical plane (Hurly, Franz, & Healy, 2010). They did not appear to beacon to the flower in spite of the 'flower' being highly conspicuous, as when we simply moved the flower about 1.5m, the birds flew nearer to the location of the missing flower, and hovered, before flying directly to the moved flower.…”