Final answer:
Male peacocks expend energy through courtship displays by exhibiting their vibrant plumage to attract females, a process driven by intersexual selection. Such displays are part of the natural selection which impact the energy budget available for parental care and survival.
Step-by-step explanation:
An example that describes how an animal expends energy in finding, selecting, or winning a mate is the case of the male peacock displaying its vibrant plumage during courtship. Male peacocks invest significant amounts of energy to maintain and showcase their colorful feathers to attract females, an example of intersexual selection. This is a visually striking form of communication that indicates the male's health and genetic quality to potential mates.
Significant energy is also spent by animals in other mating systems like monogamous, polygynous, and polyandrous relationships. These mating rituals, while necessary for reproduction, may impact the energy available for other activities, such as caring for offspring or individual survival. The intense selection pressure for these displays is a result of natural selection, as they help in the process of finding and securing a suitable mate for reproduction.