All species of loons, grebes, and auks are monogamous, with adults forming strong pair bonds that are established or reestablished each year, probably during the spring prenesting period. The extent of remating by birds mated the previous year in these groups is still largely undocumented, though at least in alcids it is fairly high, given the relatively long life-spans and the tendencies of the birds to return year after year to essentially the same territory and sometimes to the same nest site. Such conditions would promote reestablishment of contracts between previously paired birds, since it is not believed that in these birds pair or family units normally remain intact through the winter. Although in some grebes such as the horned grebe breeding site tenacity and mate fidelity may be very strong, in others such as the colonial-nesting eared grebe, there is no evidence of this and mate fidelity is poorly developed.
Available at: http://works.bepress.com/paul_johnsgard/278/