EPCs delay commitment.

from The Myth of Monogamy by David P. Barash page 42 nonfiction ~1 min read

Imagine that you are a male in one of these "last in, first out" species. Add to this the fact that ecological circumstances may dictate that you and your mate must spend considerable time apart. Not knowing for certain whether she has copulated with anyone else in the interim, your best strat­egy is to copulate often. That way, you increase the chances that yours will be the most recently deposited sperm-hence, the ones most likely to fertil­ize your mate's next egg.

All this assumes, of course, that the male and female have already made a reproductive commitment to each other-through courtship, building a nest, perhaps jointly defending a territory, and so on. In other cases, when EPCs loom large in evolution's strategic planning but the prospective pair have not yet decided to settle down together, there are alternatives to mate­ guarding or copulating often. One of these is to refrain from making a com­mitment. For example, male ring doves behave aggressively toward females that reveal by their behavior that they have recently copulated with other males. The result is to delay the pairing, which is probably adaptive, since it means that by the time a male ring dove commits himself to a female with a colorful past, she will have already revealed that past by laying fertilized eggs. It is interesting that ring doves have an unusually short duration of sperm storage, so the suspicious male does not have long to wait.

—David P. Barash, The Myth of Monogamy, p. 42