How does resting posture and orientation influence escape response in shorebirds

Birds face the challenge of avoiding predators, yet the postural adjustments they use to aid their thermoregulation (resting the bill on their back plumage and standing on one leg), may diminish their capacity to detect and escape from approaching predators. This may lead to a temperature-mediated trade-off between anti-predator and thermoregulatory behaviour. In this study, I examined the effect of posture, orientation of the bird relative to their ‘blind spot’ (gap in their visual field) and temperature on the alert and escape distances of ten shorebird species to an approaching threat (273 experiments or ‘approaches’). I predicted that: 1) heat-conserving postures would be associated with shorter FIDs (flight initiation distances; the distance at which the bird commenced fleeing from the investigator); 2) low temperatures would be linked to shorter FIDs; and 3) approaches from a bird’s blind spot would result in shorter FIDs. Phylogenetically controlled mixed models investigated patterns across all species. Head posture (backrest or forward facing) did not significantly influence alert distance (AD) or FID. Standing on two legs was associated with longer ADs. Individual species’ models revealed 2 relationships for 2 species. Approaches from within the blind spot were associated with shorter ADs and FIDs in pied oystercatcher (Haemantopus longirostris), while higher temperatures were associated with shorter FIDs in red-necked stint (Calidris ruficollis). Overall, this study reveals no strong evidence that wild-living shorebirds trade-off antipredator capacity and thermoregulatory behaviours. However, the results suggest that, in certain species, bird posture and blind spot may play roles in antipredator behaviour and this warrants further investigation across a wider variety of birds.