There are 3 types:
1. monogamy (90% of birds) 1 male; 1 female. Usually for one season but sometimes permanent in long-lived species that are either nonmigratory or that winter together. Some albatrosses always come back to exactly the same spot.
2. polygamy (9%), Lasting pair bonds with a) polygyny = 1 male + 2 females; b) polyandry = 1 female + 2 males
3. promiscuity (1%) These birds are either random maters or form leks.
Once birds court, they then begin NESTING.