Confusion and Monogamy viz. Birds
There seems to be some confusion about monogamy in the world of birds. I have heard people say that "90% of birds are monogamous" (or some variation thereof). This is based on a study in the 60's by David Lack: "In the 1960's David Lack estimated that over 90 per cent of all birds were socially monogomous [sic], an arrangement in which a male and female work together to rear offspring" (Birkhead, p. 326). The key word there is "socially." The vast majority of birds (at least small birds, passeriforms) fuck like crazy.
From an American Robin mating behavior website:
Extra-pair copulations do occur even though the American Robin is monogamous. Females actively seek EPC’s [sic] with high quality males because females want the best genes for their offspring to survive (Slagsvold, 1996). Males try to guard female mates when they are fertile, but females are still able to partake in EPC’s and if the male does not know, he will take care of offspring that are not his own! EPC's occur because the female only increases her individual fitness if her offspring have the best genes for survival. If she finds a male who seems more fit than her mate, she will copulate with him, but have her mate raise the offspring as if they were his own.
Doesn't sound monogamous in any conventional sense to me. People need to be specific. Is a bird socially or sexually monogamous (or both, or neither)?
From an American Robin mating behavior website:
Extra-pair copulations do occur even though the American Robin is monogamous. Females actively seek EPC’s [sic] with high quality males because females want the best genes for their offspring to survive (Slagsvold, 1996). Males try to guard female mates when they are fertile, but females are still able to partake in EPC’s and if the male does not know, he will take care of offspring that are not his own! EPC's occur because the female only increases her individual fitness if her offspring have the best genes for survival. If she finds a male who seems more fit than her mate, she will copulate with him, but have her mate raise the offspring as if they were his own.
Doesn't sound monogamous in any conventional sense to me. People need to be specific. Is a bird socially or sexually monogamous (or both, or neither)?