Most bird species that form flocks show a negative relations…
Most bird species that form flocks show a negative relationship between flock size and individual vigilance (i.e., the larger the flock, the less often an individual lifts its head to scan the surrounding environment). However, some bird species have shown a positive relationship between flock size and individual vigilance. The positive relationship is particularly strong when flocks are space-constrained, such as in small ponds or fields. What is the most likely explanation for this?