What birds are non mogogamous?

Answer 1

Overall, a relatively small proportion of birds tend to exhibit non-monogamous mating behaviors. The alternative to monogamy is usually called "polygamy." The different type of polygamy include polygyny (2%), polyandry (< 1%), and polygynandry (rare). The vulgar equivalents to these forms of polygamy would be a female harem, a male harem, and an orgy/over promiscuity.

Gill's Ornithology (2007) discusses mating strategies and life-history in depth, and reports that less than 10% of species are overtly non-monogamous. On the other hand, genetic analyses of lineages in several species indicate that several presumably monogamous species of birds "cheat" on their partners during the breeding season (of the species examined, only about 14% were "faithful"). The scientific term for this philandering by birds is "extra-pair copulations." Sometimes---e.g. when resources are abundant---normally monogamous birds will practice polygamy. Red-winged Blackbirds, Indigo Buntings, and Marsh Wrens, for instance, will sometimes practice polygyny when the males control high-quality territory.

Species that tend to be regularly polygynous include the Southern Red Bishop and the Golden-backed Weaver (both African). The Spotted Sandpiper is an example of a polyandrous species. Lekking is a common type of display among promiscuous birds, where males gather together in a group and display for females. The displays of Sage Grouse have actually been mimicked by humans, and Blue Manakins are famous for their elaborate performances.

There's also brood parasitism, but that's more of a general reproductive strategy than a particular mating system. As I said, Gill covers all this fairly comprehensively.