Richard Prum: prediction

Transcript context

…How well can we explain why fairy wrens are different in their mating practices? How much explanatory power does ornithology have there? We need to talk a little bit about what makes fairy wrens extraordinary in other ways. Fairy wrens live in cooperative groups, extended families that include multiple males and females of reproductive age. Usually, a large number of them are at least male offspring of previous years that are hanging around helping mom and dad or some adults raise their relatives. This probably arises — and is very common in Australian birds — it probably arises because of very high habitat variability, in particular variability in rainfall, as you see already. Thinking about Australia, we think a lot about whether there’s a drought or not, right? Under those conditions, you never really know whether you’re going to have enough resources to raise kids. Another feature is that the habitat is rich in some times of the year, and so as a result, they’re packed cheek to jowl, so there’s no real estate for the kids to go off to. They stay at home, move into the basement, and help their parents until they can inherit the back 40 or take over or bud off, if you will, into a new territory. That means there’s a lot of reproductive opportunities between groups, but the groups are in separate territories. A lot of what happens in these cooperative species like fairy wrens, people found out, is that the females mate-multiply. That is, they can mate with other members of the group besides the mature or most dominant male. Or they can mate with other males in other groups. Is it variability of rainfall that makes Australian birds weirder?…

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