Brood parasitism is indeed found in cowbirds from South America, where the genus *Molothrus* probably originated, and so although it follows that brood parasitism almost certainly evolved in that genus in the first place for reasons other than because they needed to follow a wandering mammal, the Brown-headed Cowbird's well-documented dependence on nomadic bison certainly made brood parasitism uniquely valuable for it, at least until we decimated the bison while introducing cattle.
It's virtually impossible to know the full story about any species--we're always finding out more. Learning new information doesn't mean we throw out a whole body of old but accurate observations--it means we work out how all the pieces of information, including both DNA/evolutionary biology and natural history fit together. Otherwise, we're just like the blindfolded people each describing one part of the elephant, with nobody getting the full picture. Best, Laura Erickson Duluth On Thu, Apr 22, 2021 at 4:02 PM Steve Weston <swesto...@gmail.com> wrote: > I had written in a recent post: > "Cowbirds are quite common. Habitat is forest edges, also farm yards. > Originally they apparently co-evolved with bison and it has been > hypothesized they developed their parasitism as a mechanism to breed and > leave their young behind as they followed the bison." > > While I can well document that information, Tony Hertzel informed me: > "Current thinking among evolutionists says that brood parasitism in > cowbirds first evolved in South America millions of years before > Brown-headeds were around and well away from any bison. The concept of the > species co-evolving with bison makes no sense when you think about how that > might occur." > I can definitely see how that hypothesis could have been developed with > little factual information to support it. Thank you, Tony! > > Steve Weston > On Quigley Lake in Eagan, MN > swest...@comcast.net > > ---- > Join or Leave mou-net: http://lists.umn.edu/cgi-bin/wa?SUBED1=mou-net > Archives: http://lists.umn.edu/archives/mou-net.html > > During the pandemic, the MOU encourages you to stay safe, practice social > distancing, and continue to bird responsibly. > -- Laura Erickson Duluth, MN she/her/hers For the love, understanding, and protection of birds www.lauraerickson.com www.patreon.com/lauraerickson You were made and set here to give voice to this, your own astonishment. —Annie Dillard Please consider the environment before printing this e-mail. ---- Join or Leave mou-net: http://lists.umn.edu/cgi-bin/wa?SUBED1=mou-net Archives: http://lists.umn.edu/archives/mou-net.html During the pandemic, the MOU encourages you to stay safe, practice social distancing, and continue to bird responsibly.
