Females usually choose their mates; this is intersexual selection.

• Elaborate courtship rituals among the Western Grebe ensure his commitment.

• Marmot males demonstrate reproductive fitness by controlling resources.

• A male may bring an item of value - a "nuptial gift" - as a sign of his reproductive fitness.

• Fancy and bright plumage demonstrates a male's fitness; females are usually less colorful.
  

Exceptions occur when the male has a heavy reproductive investment.