European starlings use their acute vision to check on feline predators but not on conspecifics

Abstract

Head movements allow birds with laterally placed eyes to move their centers of acute vision around and align them with objects of interest. Consequently, head movements have been used as indicator of fixation behavior (where gaze is maintained). However, studies on head movement behavior have not elucidated the degree to which birds use high-acuity or low-acuity vision. We studied how European starlings (Sturnus vulgaris) used high-acuity vision in the early stages of visual exploration of a stuffed cat (common terrestrial predator), a taxidermy Cooper’s hawk (common aerial predator), and a stuffed study skin of a conspecific. We found that starlings tended to use their high acuity vision when looking at predators, particularly, the cat was above chance levels. However, when they viewed a conspecific, they used high acuity vision as expected by chance. We did not observe a preference for the left or right center of acute vision. Our findings suggest that starlings exposed to a predator (particularly cats) may employ selective attention by using high-acuity vision to obtain quickly detailed information useful for a potential escape, but exposed to a social context may use divided attention by allocating similar levels high- and low-quality vision to monitor both conspecifics and the rest of the environment.

Modelling non-attentional visual information transmission in groups under predation

“…These results point to an explanation for the observations described by Lima (1995): one bird detecting danger and fleeing, and only some others reacting. The results also agree with the observations of Butler et al (2016): starlings significantly oriented their high-acuity vision towards a threat but not towards their conspecifics. Caraco & Bayham (1982) also found that in the observed house sparrows, the sparrows oriented themselves such that they can keep track of the neighbours.…”

The visual social environment affects non-additively neighbor spacing and interaction time in zebrafish

“…Finally, separation distance was longer when zebrafish used high relative to low acuity vision in the low visual social risk scenario, but the difference in the visual field region used vanished in the high social risk scenario. Birds have also been shown to vary their use of high vs. 21 low acuity vision depending on perceived individual risk (i.e., exposure to a predator model vs. conspecific model; Butler and Fernández-Juricic 2018). In the case of zebrafish, under low perceived social risk, it is possible that individuals were able to divide their visual attention and adjust their spacing depending on which portion of their visual field they were using at the moment of visually inspecting the conspecific.…”

“…Additionally, low density fish schools could detect predators more quickly because of greater group visibility (Rountree and Sedberry 2009;Pita et al 2015). In these low-density groups, individuals may orient themselves utilizing regions of the visual field with low acuity to monitor changes in conspecific behavior while the centers of acute vision may be focused on the environment for threats (Butler and Fernández-Juricic 2018). The presence of a threat could be quickly transmitted across the group via social information, leading to rapid changes in the spatial configuration of the school ending in spatially tighter (e.g., higher density) schools.…”

The (Under)Use of Eye-Tracking in Evolutionary Ecology

“…Several avian eye-tracking studies to date have shown that animals are capable of rapidly modulating how they allocate attention in response to environmental changes in order to maximise fitness. For example, European starlings (Sturnus vulgaris) are more likely to fixate on the predator (versus non-threat) stimuli if they are present simultaneously [28,29] and peafowl (Pavo cristatus) exhibit decreased fixation on conspecifics in the presence of a predator [20].…”