ability of predators to detect the forager, as well as the likelihood that the forager can escape the predator if it is not vigilant. Animals prioritise vigilance over feeding when the predation risk is high. For example, yellow-eyed juncos spend more time scanning for predators when a potential predator, a Harris's hawk (Parabuteo unicinctus), is present compared to when the hawk is absent. Another factor that influences vigilance is the benefit that is expected from foraging in the absence of predation. This is dependent on the quality of the food as well as the energetic state of the individual. If there is much to be gained from feeding, foragers may forgo vigilance. Similarly, if hungry animals have a higher chance of dying from starvation than from predation, it is more beneficial to sacrifice vigilance to fulfill their energy requirements. When three-spined sticklebacks (Gasterosteus aculeatus) are deprived of food, they prefer to feed in locations with a high density of water fleas. The cost to this choice is that the sticklebacks must concentrate on picking out the prey due to the 'predator confusion effect' where many moving targets make it difficult for predators to pick out individual prey. This choice means that the sticklebacks are less able to scan for predators however the risk of starvation is relatively higher than the risk of predation. Similarly, juncos that have been deprived of food exhibit lower levels of vigilance, instead focusing on rapid feeding which is a behaviour incompatible with scanning. Habitat and food choice The state of an animal can change due to its behaviour and vice versa due to the dynamic feedback between foraging, body reserves and predation risk. The feedback can influence an individual's choice of where, when and what to feed on. If the predation risk is so great that an animal must maintain a level of vigilance that drastically inhibits feeding, it may opt for an alternative. For example, the bluegill sunfish (Lepomis macrochirus) has the choice of foraging on plankton in the safety of reeds or on benthic invertebrates which are a better quality food source. When a predator (the largemouth bass) is present, smaller sunfish spend the majority of their time foraging in the reeds despite this choice reducing their food intake and seasonal growth rate. Sunfish that are too large to be eaten by the bass forage almost entirely on benthos. Although staying in the