Answer
Monogamy is so common in birds because male and female birds are equally skilled when it comes to parenting skills and parental care. In mammals, the primary care often falls upon the female of the pairing, as mammal offspring require milk--which only the female can offer. As birds do not rely on this lactation, both male and female parents are able to contribute to offspring care in equal ways. This likely accounts for the dependence on monogamy.
Work Step by Step
Monogamy is so common in birds because male and female birds are equally skilled when it comes to parenting skills and parental care. In mammals, the primary care often falls upon the female of the pairing, as mammal offspring require milk--which only the female can offer. As birds do not rely on this lactation, both male and female parents are able to contribute to offspring care in equal ways. This likely accounts for the dependence on monogamy.
