Chicago Wildlife Watch Talk

Non migratorius

  • ForestPreserve by ForestPreserve moderator

    Like many others, this Turdus is skipping the "migratorius" part. At least it's finding food, but the projected high tomorrow is 13 F / -11 C.


  • gardenmaeve by gardenmaeve

    Looks like it's finding some berries, anyway!


  • mason_UWI by mason_UWI scientist

    Many individuals of a species, Robins included, will not migrate if there are sufficient resources (i.e. food) to overcome the negative effects of winter (e.g. the energetic cost of staying warm in freezing temperatures). This strategy is often called "bet hedging", the robin is decreasing its temporal variance in its fitness, and by doing so accepts an overall decrease in fitness (dry scientific description).

    So what's that actually mean to our rust-breasted friend? No doubt a robin in Florida has a lower energetic cost than our Illinois robin (its warmer), but it had to fly all the way down there in order to gain those benefits. By making the decision to not migrate the robin is accepting the fact that it will be cold, in the hopes that the energy spent staying warm will be less than the cost of migrating. It's a roll of the dice, and often it pays off. A bird that does not migrate is already where it needs to be, and can lock down prime nesting habitat way before any of the other migratory birds arrive.

    Bet hedging is really interesting, and is a great way to introduce game theory into ecology. Many species all over the world hedge their bets one way or another!


  • WillowSkye by WillowSkye

    Awesome 😃