Self-study
In an island nature preserve, Common Eider nests are found in roughly equal numbers in highly concealing woody vegetation, wooden boxes, and open grasslands that do not conceal nests. ████ ██████ ██████ ███ █████ ████ ██ █████ ███████████ ██ █████ ██████ ███████ ████████ ██ █████ ██ ██████ ████ ██ ██ ████ ████ ██ █████████ ████ ████ ██████████ ████████ ███ █████ ██████ ███ █████ █████████ ██ █████ ██████████ ██ ██ ████ ████████ ████████ ██ █████ ███████ ███ ██████ █████ █████ ███ ██████ ██████ ██████ ████ ███ █████ ████ ██ █████ ██████ █████ ████ ████████ ██████ ███████████ █████ ██ ██████ ██████
"Surprising" Phenomenon
Common Eiders who use previously-established nests tend to use wooden box nests, rather than the seemingly-safer woody vegetation nests.
Objective
The right answer will be a hypothesis that explains a key difference between established wooden box nests and established woody vegetation nests. That difference will result in the wooden box nests being more attractive to Common Eiders, likely for some reason other than maximal protection from predators.
18.
Which one of the following, ██ █████ █████ ████ ████ ██ ███████ ████ ██ ████ ██████ █████████ ██████ ██████ ████ ███ █████ ████ ██ █████ ██████ █████ ████ ████████ ██████ ███████████ █████ ██ ██████ ██████
a
Some Common Eiders ████ ███ █████ ████ ██ █████ ███████████ ██ █████ ██████ ██████ ████ ████ █████████ ██ ██████████ ██████ ████████ █████ ██ █████ ███ ██ ███ ██████ █████████
It doesn't matter what some Common Eiders did years later. We need to know why, when they borrow established nests, they generally choose nests that aren’t maximally-protected from predation.
b
Established nests concealed ██ █████ ██████████ ███ █████████ ███ ██████ ██████ ██ ███████
In other words, Common Eiders choose the wooden box nests because they can't find anything better. Woody vegetation nests are difficult to detect, which explains why Common Eiders choose the next-best option.
c
Defensive behavior by ████ ████████ ███ █████████ █████ █████████ ██████ ███████
For this to work, we would need to know that woody vegetation nest builders are more defensive than wooden box nest builders. We don’t know that, so this isn't a useful explanation.
d
Virtually all of ███ ██████ ██████ ████████ ████████ ██ ████████ ████ ████ █████ ██ ████ █████ ██ ███ █████ ███████ ██ ███████
The stimulus doesn’t tell us that human alteration makes a difference. Besides, this doesn't differentiate the wooden box nests from the woody vegetation nests—they're both in altered habitats.
e
Foxes and other ███████ █████████ ██ ███ ██████ █████ ███ ███ ████████ ██ ███ ██████ ██████ █████████
If predators are common, why aren’t Common Eider choosing the best-protected nests? This simply intensifies the paradox in the stimulus.