(1)Michael J. Vandeman, Ph.D., says when an animal is guarding a nest, it can be scared away ("flushed") for some time, at least while a human is present. Besides using up energy that may not be plentiful, eggs and young are left exposed to dangerous temperatures (hot or cold) and predators. The movement of the parent, or sometimes the odor of the human, can direct predators to the nest, causing the death of some of the young. Sometimes the parent in its rush steps on an egg or knocks it or its young out of the nest, leading to certain death for the offspring. Some parents may even abandon the nest or kill and eat the young, if they are frightened or startled enough. Young can get left behind when a parent flushes suddenly, get lost, and die of starvation or be eaten by a predator.
He goes on to say the stress of disturbance can increase energy needs, elevate heart rate (possibly leading to death), force the animal to temporarily or permanently abandon a feeding area, force it to become nocturnal, force it to spend a great amount of time watching for humans, interfere with reproduction, and in general decrease its productivity. Migratory birds, for example, have a limited amount of time to stock up on food before their trip. They often spend long periods flying over ocean, and can die if they don't have adequate nutritional reserves. So, it seems that wherever we go to escape we are in many ways harming wildlife.
