Final answer:
Monogamy is a mating system where one male is paired with one female for at least one breeding season. This system has evolved due to several reasons, including mate-guarding, male-assistance, and female-enforcement. In birds, monogamy is common and the male also provides parental care for the offspring.
Step-by-step explanation:
In monogamous systems, one male and one female are paired for at least one breeding season. Several explanations have been proposed for this type of mating system. The 'mate-guarding hypothesis' states that males stay with the female to prevent other males from mating with her.
Another explanation is the 'male-assistance hypothesis,' where males that remain with a female to help guard and rear their young will have more and healthier offspring. Monogamy is observed in many bird populations where, in addition to the parental care from the female, the male is also a major provider of parental care for the chicks. A third explanation for the evolutionary advantages of monogamy is the 'female-enforcement hypothesis.' In this scenario, the female ensures that the male does not have other offspring that might compete with her own, so she actively interferes with the male's signaling to attract other mates.