by Tina Yerkes, Ph.D.
Why in the world, I've been asked many times, would you spend years in a dilapidated trailer in prairie Canada with no water or heat, studying redheads? Because, I've invariably answered, they are cool ducks, and don't you know why redheads are so interesting?
At that point, I get a lot of blank, strange looks, and then I proceed to tell the story of a day in the life of the parasite queen: the hen redhead.
Most female ducks arrive on their breeding grounds with a simple decision to make: lay eggs or don't. Female redheads, on the other hand, have several different paths available to them: don't lay eggs; lay eggs in their own nest; lay eggs in another female's nest; or lay eggs in another female's nest and lay eggs in their own nest.
When females lay their eggs in another duck's (the host's) nest, it is called brood parasitism. There are two types of parasitism: when females lay eggs in nests of their own species, and when females lay eggs in nests of other species. Female redheads do both.
Dual-strategy females, those that parasitize other ducks' nests and then lay eggs in their own nest, always parasitize first and then build a nest, lay eggs, and care for their young. (Parasitic eggs receive no care from biological mothers, but instead rely on the charity of host hens.)
To make this even more complicated, individual female redheads often do different things from one year to the next. One year they may only parasitize, and the next they may lay in their own nest. At this point in the story, I get astonished, puzzled looks and more questions.
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How do redhead females decide what to do each year? What are the benefits of parasitism to redheads? And doesn't it harm the host female? Now I have my audience hooked, and I know I'm creating a future redhead fan.