Zach and I were reading A Country Scrapbook by Lilias Rider Haggard, when we came across the passage below. The book was written around World War II, and refers to a centuries old belief that osprey (a piscivorous bird) had some sort of hypnotic effect on fish, causing them to roll over and point their bellies towards the sun. This behavior sounds very familiar, as the trematode parasite I study induces this behavior in California killifish in order to increase predation rates by birds, which are the next host in the parasite’s life cycle. I don’t know the fish species in which this behavior was observed, but it’s possible that folks were attributing to ospreys a behavior that may have been induced by the fish’s parasites. I wonder what they would think if they knew!

*Edit: I incorrectly indicated that this belief was held around WWII, when the book was referring to a belief held centuries before.

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From A Country Scrapbook by Lilias Rider Haggard:

“The event of the month has been the arrival of an osprey or fish-hawk. The osprey is a bigger bird than he looks, and it is only when he passes near the house one realises his five feet of wing span, six inches more than the heron. He beats up and down the valley and fishes over the river, turning into the wind to hover like some oversized kestrel, a characteristic action.

Centuries ago when the osprey was common in England and robbed the monastic stew ponds, this hovering was supposed to have a mesmeric effect, and as the shadow of his wings fell on the water the fish were believed to turn over on their white bellies, making them easy prey. Thus the lines:

I will provide thee of a princely osprey,
That as he flieth over fish in pools
The fish shall turn their glistening bellies up
And thou shalt take liberal choice of all.”