Question

A wildlife biologists has adopted a number of techniques to protect the Willow Flycatcher, a bird that often nests and feeds in willows. Some techniques reflect top-down while some reflect bottom up control. Which of the following approaches demonstrates her understanding of how top-down forces affect community dynamics?
A) The biologists attempts to increase food availability by reintroducing beaver. She hypothesized that beaver will raise the water table, stimulating the growth of willow, which will result in an increase in insect abundance, giving flycatchers more food.
B) Willow Flycatchers can lose eggs to squirrels, weasels, and other predators. The biologist attempts to protect nests by putting metal collars around the base of the windows that keep ground predators from climbing up to reach the nests.
C) Both approaches rely on bottom-up forces.
D) Neither approach relies on bottom up forces.

Answer 1

Answer:

B) Willow Flycatchers can lose eggs to squirrels, weasels, and other predators. The biologist attempts to protect nests by putting metal collars around the base of the windows that keep ground predators from climbing up to reach the nests.

Explanation:  

The dynamic of a species depends on its interaction with other species. So in species management plans, among other aspects, it is important to know the trophic webs in which a species is involved and the interactions of that taxonomic group with the others in the chain.

Top-down techniques take decisions from the most global variables to the most inferior or specific ones. When referring to the trophic web, the most global variables are related to top predators, while the most inferior ones are related to the first levels of the chain.

If the researcher needs to adopt a top-down technique, the most suitable one to choose is to protect the Flycatcher´s nests from predators. Predators are the carnivores in the chain that feeds on the Flycatchers´ eggs. This action will interrupt the link between the superior predators and the flycatchers, allowing this last species to recover its population size.