Antipredator behavior: escape flights on a landscape slope

Few studies have reported flight responses of prey on landscape slopes in the wild, and little theoretical work is available. We present a formal model to predict whether prey should move up or down the hillside after detecting a perched raptor as determined by the duration of the attack once launched by the predator, perching height of the predator, and the landscape slope. We recorded escape responses of blue tits Cyanistes caeruleus and great tits Parus major when approached by a human in the field. This was done in the postfledging period, when the demand for food is high, and when the families usually move to a new site, presumably perceived to be safer, to continue foraging after being exposed to a predator. We found that great tit families, which prefer to forage close to the ground, flew uphill, matching the model’s prediction. However, blue tit families, which forage higher in the canopy, did not move uphill but moved higher up in the trees. Vertical movement upward may be the safest option if the predator is located on the ground. Modeling escape flights may encourage detailed studies of attack and escape behaviors in animals and provide insights in predator–prey interactions in general.