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 Why do canvasbacks parasite their nest with redheads and vice versa?
-Chason Bowman
Answer:
Hey Chason!
Redheads are actually known to parasitize canvasback nest more then a canvasback will parasitize a redhead nest. Studies have shown that redheads can parasitize 50-80% of canvasback nests. Parasitism between these two species is common because they are sympatric, meaning they occupy roughly the same habitat requirement within the same breeding seasons, but do not interbreed. Parasitism between these two species of waterfowl is also common because they have precocial young (young that display independent activity at birth), and are not fed by their parents. So the female host (usually the canvasback hen) would not expend any extra energy incubating and rearing 15 ducklings as she would if she had 10. Additional young in a brood could also buffer the host’s progeny from predation. However, if the female host resists the parasitic female as she approaches the nest and attempts to lay, it could draw attention to the nest location making in more susceptible to predation, or increase the chances of eggs being cracked, dislodged, or displaced from the nest bowl. Looking from the redhead’s point of view, unloading a few extra eggs onto another female increases her nesting productivity and adds a few more of her youngsters into the gene pool.
What a great question Chason, I hope I was able to help. We had some spectacular flocks of canvasback work into the decoys this fall at the Delta Marsh Manitoba. What a beautiful and fascinating bird! I hope you enjoy them as much as I do…they are heading your way as we speak!
Sincerely
Carly Michie - Delta Waterfowl Biologist
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